Tamper-resistant sensors with one or more shaped, flexible layers

Abstract

Tamper-resistant assembly (600; 800; 1500; 2100) which exhibits: a tamper-responsive sensor (500; 605; 610, 611, 612; 811, 821; 821, 822; 1200; 1510, 1520; 1510', 1520'), wherein the tamper-responsive sensor has: at least one shaped, flexible layer (510; 1700) with a first side (511; 1701) and a second side (512; 1702) opposite the first side, wherein the at least one shaped, flexible layer has surface curvatures (513) extending from the first side and surface curvatures (513) extending from the second side, wherein the at least one shaped, flexible layer is folded together as at least one flattened, folded-over layer; and Circuit lines (501; 1705) forming at least one resistance network, wherein the circuit lines are arranged on the first side and / or the second side of the at least one shaped, flexible layer, wherein the circuit lines are at least partially wrapped around the surface curvatures extending from the at least one of the first sides or the second side of the at least one shaped, flexible layer.

Description

BACKGROUND

[0001] Numerous activities require secure electronic data transmissions. To facilitate secure electronic data transmissions, an encryption / decryption system can be implemented on an electronic assembly or printed circuit board assembly contained in equipment connected to a data transmission network. Such an electronic assembly is a tempting target for criminals because it may contain codes or keys for decrypting intercepted messages or encrypting fraudulent messages. To prevent this, an electronic assembly can be mounted in a housing, which is then encased with a security sensor and encapsulated with polyurethane resin.A security sensor, in one or more embodiments, may be a sheet or layer of insulating material on which circuit elements, such as conductive traces, are fabricated in a confined space. The circuit elements are destroyed if the sensor is torn, and the tear can be detected, generating an alarm signal. The alarm signal can be transmitted to a monitoring circuit to reveal an attack on the integrity of the assembly. The alarm signal can also trigger the erasure of encryption / decryption keys stored within the electronic assembly.

[0002] The document US 2002 / 0 084 090 A1 relates to an electronic circuit article with tamper detection, comprising: a layer of flexible dielectric having a first side and a second side; a screen-printed pattern of flexible, electrically conductive first circuit lines forming a first resistance network on the first side; and a photolithographically produced pattern of flexible, electrically conductive second circuit lines forming a second resistance network on the second side.

[0003] The document US 2012 / 0 047 374 A1 relates to an electronic device comprising: a printed circuit board with electronics mounted thereon; a housing substantially surrounding the printed circuit board, the housing comprising at least a first part attached to a second part, the printed circuit board being mounted to the second part; a security shield covering a first region of the printed circuit board and configured to detect tampering, the security shield being integrated into the first part of the housing, a second region of the printed circuit board being covered by the housing and located outside the security shield, both the first and second regions containing electronics;one or more pressure-sensitive switches mounted on the circuit board within the first region, wherein the first portion of the housing includes one or more features that engage the one or more pressure-sensitive switches such that movement of the first portion away from the circuit board causes the one or more pressure-sensitive switches to disengage; and security electronics on the circuit board within the high-protection region connected to the security shield and the one or more pressure switches, the security electronics configured to zero the data stored in the first region of the circuit board if the security shield detects tampering or if one or more of the one or more pressure switches are released.

[0004] The document US 2015 / 0 307 250 A1 relates to a packaging for important and high-value items for the purpose of preventing counterfeiting, which is made of at least one single-layer material with a protective agent, characterized in that the packaging is made of at least two material layers that are monolithically bonded by means of a chemical bond, by gluing or by heat sealing with copolymers or coextrusive polyethylenes, in the form of a container with a housing, a bottom and a lid or in the form of an adhesive tape that wraps around the packaged object, wherein the bonded surfaces of the packaging components or adhesive tape sides are parallel or at an angle of 0.01° to 90.0° to each other, with a locking connection that is made in the form of at least one step between the mating surfaces,wherein at least one of the locking connection surfaces has at least one additional protective means that can be destroyed if tampered with. SUMMARY

[0005] The invention is based on the object of creating a tamper-evident assembly and its manufacturing method, as well as a component of an electronic assembly, wherein the tamper-evident assembly and the component of an electronic assembly provide improved protection against tampering. This object is achieved by the features of the corresponding independent claims.

[0006] Provided herein, in one or more aspects, is an improved tamper-evident assembly including, for example: a tamper-evident sensor. The tamper-evident sensor includes: at least one shaped flexible layer having opposing first and second sides; circuit lines forming at least one resistive network, wherein the circuit lines are disposed on at least one of the first side and the second side of the at least one shaped flexible layer; and wherein the at least one shaped flexible layer having bends with the circuit lines, and the circuit lines at least partially overlie the bends of the at least one shaped flexible layer.

[0007] In another aspect, an electronic assembly component is provided, including, for example: an electronic assembly; an electronic assembly housing at least partially enclosing the electronic assembly; and a tamper-responsive electronic circuit structure associated with the electronic assembly housing. The tamper-responsive electronic circuit structure includes a tamper-responsive sensor.The tamper-responsive sensor includes, for example: at least one shaped, flexible layer having opposing first and second sides; circuit lines forming at least one resistive network, wherein the circuit lines are disposed on at least one of the first side and the second side of the at least one shaped, flexible layer; and wherein the at least one shaped, flexible layer having circuit lines has bends, and the circuit lines are at least partially overlying the bends of the at least one shaped, flexible layer.

[0008] In another aspect, a manufacturing method is provided that includes manufacturing a tamper-responsive assembly. The manufacturing includes providing a tamper-responsive sensor. Providing the tamper-responsive sensor includes: providing at least one shaped, flexible layer having opposing first and second sides; disposing circuit lines comprising at least one resistor network on at least one of the first side and the second side of the at least one shaped, flexible layer; and wherein the at least one shaped, flexible layer having bends with the circuit lines, and the circuit lines at least partially overlie the bends of the at least one shaped, flexible layer.

[0009] Additional features and advantages are realized by the techniques of the present invention. Other embodiments and aspects of the invention are described in detail herein and are considered part of the claimed invention. BRIEF DESCRIPTION OF THE DIFFERENT VIEWS OF THE DRAWINGS

[0010] One or more aspects of the present invention are particularly pointed out and expressly claimed by way of example in the claims at the end of the specification. The above and other objects, features, and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: Fig. 1 is a partially cutaway view of one embodiment of a tamper-resistant electronic package that may include a tamper-responsive electronic circuit structure; Fig. 2 is a cross-sectional view in elevation of one embodiment of a prior art tamper-evident electronic package including an electronic circuit; Fig. 3A illustrates an embodiment of a tamper-responsive sensor having one or more flexible layers and circuit lines forming at least one tamper-detection network; Fig. 3B is a cross-sectional view of another embodiment of a tamper-responsive sensor in elevation; Fig. 3C is a cross-sectional elevation view of another embodiment of a tamper-responsive sensor; Fig. 3D is a cross-sectional view of another embodiment of a tamper-responsive sensor in elevation; Fig. 3E is a cross-sectional elevation view of another embodiment of a tamper-responsive sensor; Fig. 4A is a partial illustration of one embodiment of a tamper-responsive sensor having a corrugated layer of flexible dielectric with circuit lines; Fig. 4B is an alternative embodiment of a tamper-responsive sensor having multiple corrugated layers of a flexible dielectric with circuit lines; Fig. 5A is an embodiment of a tamper-responsive sensor having a flattened, folded layer with circuit lines; Fig. 5B is a partial plan view of the flattened, folded layer with circuit lines of Fig. 5A is; Fig. 5C is a partial cross-sectional elevation view of a tamper-responsive sensor having a flattened, folded layer with circuit lines and at least one other layer overlying one or both sides of the flattened, folded layer; Fig. 5D shows another embodiment of the tamper-responsive sensor of Fig. 5C, further including a frangible layer for enhanced tamper detection capability; Fig. 5E is a partial cross-sectional elevation view of a tamper-responsive sensor having a flattened, folded layer with circuit lines and at least one other layer overlying the bottom surface of the flattened, folded layer; Fig. 5F is a partial cross-sectional elevation view of another embodiment of a tamper-responsive sensor having a flattened, folded-over layer with circuit lines sandwiched between two other layers overlying opposite sides of the flattened, folded-over layer; Fig. 5G illustrates a partial cross-sectional elevation view of another embodiment of a tamper-responsive sensor having a plurality of flattened, folded-over layers with circuit lines separated by at least one other layer in a stack of layers; Fig. 5H illustrates a partial cross-sectional elevation view of another embodiment of a tamper-responsive sensor comprising a stack of layers including a plurality of flattened, folded-over layers with circuit lines and a plurality of other layers, for example, a plurality of other flexible layers disposed above and / or below the flattened, folded-over layers with circuit lines; Fig. 6A is a cross-sectional elevation view of a tamper-respondent assembly comprising an electronics housing and a tamper-respondent electronic circuit structure having a tamper-respondent sensor, the tamper-respondent sensor comprising a flattened, folded-over layer with circuit leads wrapped around the electronics housing; Fig. 6B is a cross-sectional elevation view of a tamper-respondent assembly comprising an electronics package and a tamper-respondent electronic circuit structure having a plurality of tamper-respondent sensors, the tamper-respondent sensors comprising a plurality of discrete flattened, folded-over layers of circuit lines, with a flattened, folded-over layer wrapped and doubled along the edge or side of the package around the flattened, folded-over layers of circuit lines located above and below the package; Fig. 6C is a plan view of an embodiment of the tamper-responsive assembly of Fig. 6B from above (or from below); Fig. 6D is a cross-sectional elevation view of another embodiment of a tamper-respondent assembly including an electronics housing and a tamper-respondent electronic circuit structure having a plurality of tamper-respondent sensors, wherein the tamper-respondent sensors include a plurality of flattened, folded-over layers with circuit leads, and one flattened, folded-over layer is wrapped along the edge of the electronics housing and the other flattened, folded-over layers located above and below the electronics housing are wrapped around the flattened, folded-over layer positioned around the edge of the electronics housing; Fig. 6E is a plan view of one embodiment of an upper (or lower) tamper-responsive sensor for use in a tamper-responsive assembly, such as that shown in Fig. 6D, wherein the upper (or lower) tamper-responsive sensor is shown as a flattened, folded-over layer, for example only; Fig. 6F is a plan view of another embodiment of an upper (or lower) tamper-responsive sensor in a tamper-responsive assembly, such as shown in Fig. 6D, wherein the upper (or lower) tamper-responsive sensor is shown as a flattened, folded-over layer, for example only; Fig. 6G is a cross-sectional elevation view of another embodiment of a tamper-respondent assembly including an electronics housing and a tamper-respondent electronic circuit structure having a plurality of tamper-respondent sensors, wherein the tamper-respondent sensors include two flattened, folded-over layers with circuit lines surrounding and overlapping the electronics housing along the edge or side thereof; Fig. 7A is a plan view of one embodiment of a first tamper-responsive sensor to be interwoven with a similarly constructed second tamper-responsive sensor; Fig. 7B is a plan view of one embodiment of a tamper-responsive electronic circuit structure having two discrete tamper-responsive sensors, such as in Fig. 7A, which are woven into an interwoven multi-sensor layer; Fig. 7C illustrates, as another example, a stack of interwoven multiple sensor layers that may be used, for example, in conjunction with an electronics housing within a tamper-evident assembly to define a secure space; Fig. 8A is a cross-sectional elevation view of one embodiment of a tamper-responsive assembly or tamper-resistant electronic device including (in part) a tamper-responsive sensor integrated into a multilayer printed circuit board; Fig. 8B is a top view of the multilayer printed circuit board of Fig. 8A, which is an embodiment of the safe space where it is partially defined within the multilayer printed circuit board; Fig. Figure 9 is a partial cross-sectional elevation view of a tamper-responsive assembly including (in part) a multilayer printed circuit board and an integrated tamper-responsive sensor; Fig. 10 illustrates one embodiment of a process for fabricating a multilayer printed circuit board with an integrated tamper-responsive sensor; Fig. 11 is a partial cross-sectional elevation view of a tamper-responsive assembly including an electronics package and an associated tamper-responsive sensor, and a multilayer printed circuit board with an integrated tamper-responsive sensor therein; Fig. 12 illustrates an embodiment of a process for attaching a tamper-responsive sensor to an internal surface of an electronics package, for example, for use with a device described herein with reference to Fig. 8A to 11; Fig. 13A is an isometric bottom view of an embodiment of an electronics package, such as that shown in Fig. 8A, Fig. 11 & 12, and illustrates placement of an inner sidewall tamper-responsive sensor over an inner sidewall surface of the electronics enclosure; Fig. 13B the structure of Fig. 13A, wherein an inner major surface tamper-responsive sensor is provided over an inner major surface of the electronics enclosure, and wherein the illustrated inner major surface tamper-responsive sensor at least partially overlaps the inner sidewall tamper-responsive sensor; Fig. 13C is an enlarged view of a corner of the electronics housing and the tamper-responsive sensors of Fig. 13B, which illustrates that the inner major surface tamper-responsive sensor is located at an inner corner of the electronics housing above the inner sidewall tamper-responsive sensor, is an invention; Fig. 14A is an isometric bottom view of an embodiment of an electronics housing or electronic assembly housing, such as shown in Fig. 13A to 13C; Fig. 14B is an enlarged view of the inner side wall corner of Fig. 14A, illustrating the area 14B thereof; Fig. 15A is a bottom perspective view of an embodiment of a tamper-responsive assembly including an electronics package such as that shown in Fig. 14A to 14B; Fig. 15B is an exploded view of the tamper-responsive assembly of Fig. 15A; Fig. 16A is an isometric view of one embodiment of an inner sidewall tamper-responsive sensor for covering an inner sidewall surface of the electronics package, such as shown in Fig. 14A is shown; Fig. 16B is an isometric bottom view of the electronics housing and the tamper-responsive sensor located on the inner side wall of Fig. 15A & 15B, wherein the inner sidewall tamper-responsive sensor is shown positioned over the inner sidewall surface of the electronics enclosure; Fig. 16C is an enlarged view of the tamper-responsive assembly of Fig. 16B, illustrating a portion 16C thereof; Fig. 17A an enlarged view of the Fig. 15A & 15B illustrated embodiment of the tamper-responsive sensor located on an inner major surface; Fig. 17B shows the tamper-responsive sensor located on the inner main surface of Fig. 17A, the corner tabs of which are shown erected for positioning, as in Fig. 15A & 15B illustrates, represents; Fig. 17C the tamper-responsive assembly of Fig. 15A & 15B, in which the tamper-responsive sensor is positioned on the inner major surface and from which the one or more security elements are removed; Fig. 18 is a perspective view of the one or more security elements shown in Fig. 15A & 15B, for the illustrated tamper-responsive assembly; and Fig. 19A is a partial cross-sectional elevation view of another embodiment of a tamper-responsive assembly including a structure with a rigid surface and a tamper-responsive sensor attached to the rigid surface of the structure; Fig. 19B is a cross-sectional elevation view of another embodiment of a tamper-responsive assembly having a tamper-responsive sensor attached to an electronics package and to a rigid surface of another structure, such as a heat spreader; Fig. 20A is a partial isometric view of another embodiment of a tamper-responsive sensor for a tamper-responsive assembly; Fig. 20B is a partial isometric view of another embodiment of a tamper-responsive sensor for a tamper-responsive assembly; Fig. 21A is a cross-sectional elevation view of another embodiment of a tamper-responsive assembly having first and second tamper-responsive sensors attached to an electronics package; Fig. 21B is an isometric view of an embodiment of a tamper-responsive sensor located on an inner major surface having one or more conductive traces in one or more connection regions thereof; and Fig. 21C is a cross-sectional view of the tamper-responsive assembly of Fig. 21A in elevation showing an attempted attack through the electronics housing and an adhesive appearing on the one or more conductive traces. DETAILED DESCRIPTION

[0011] Aspects of the present invention and certain features, advantages, and details thereof are described in more detail below with reference to the non-limiting example(s) illustrated in the accompanying drawings. Descriptions of well-known materials, manufacturing tools, machining techniques, etc., are omitted in order not to unnecessarily obscure the invention in detail. It is to be understood, however, that the detailed description and specific example(s), while illustrating aspects of the invention, are intended to be illustrative and not limiting. Various substitutions, modifications, additions, and / or arrangements within the spirit and / or scope of the underlying inventive concepts will become apparent to those skilled in the art from this disclosure.It should further be noted that reference is made below to the drawings, which are not drawn to scale for clarity, wherein the same reference numerals used throughout the various figures identify the same or similar components. It should also be noted that numerous inventive aspects and features are disclosed herein, and each disclosed aspect or feature, unless inconsistent, may be combined with any other disclosed aspect or feature as desired for a particular application to create a secure space around an electronic component or assembly to be protected.

[0012] First, Fig. 1 of the drawings, which illustrates one embodiment of an electronic assembly component 100, configured for discussion purposes as a tamper-resistant electronic assembly component. In the illustrated embodiment, an electronic assembly package 110 is provided, for example, containing an electronic assembly that, in one embodiment, may include a plurality of electronic components such as an encryption and / or decryption module and associated memory. The encryption and / or decryption module may include security-relevant data, for example, where access to the data stored in the module requires use of a variable key, and the type of key is stored in the associated memory within the package.

[0013] In one or more implementations, a tamper-resistant electronic component such as the one illustrated is designed or arranged to detect attempts to tamper with or penetrate the electronic assembly package 110. Accordingly, the electronic assembly package 110 further includes, for example, monitoring circuitry that, when tampering is detected, activates an erasure circuitry to erase data stored in the associated memory as well as in the encryption and / or decryption module in the data transfer card. These components may be mounted on and interconnected by a multilayer circuit board, such as a printed circuit board or other multilayer substrate, and powered internally or externally by a power supply provided within the electronic assembly package.

[0014] In the illustrated embodiment, and as one example only, the electronic assembly package 110 may be surrounded by a tamper-evident sensor 120, an encapsulant 130, and an outer, thermally conductive housing 140. In one or more implementations, the tamper-evident sensor 120 may include a tamper-evident laminate wrapped around the electronic assembly package 110, and the encapsulant 130 may be provided in the form of a molded part. The tamper-evident sensor 120 may include various detection layers monitored, for example, by a ribbon cable through the package monitor for sudden, forcible attempts to enter the package 110 and damage the package monitor or the erasure circuitry before data can be erased from the encryption module.The tamper-responsive sensor may, for example, be any such product commercially available or described in various publications and issued patents, or any improved product such as disclosed herein.

[0015] For example, the tamper-responsive sensor 120 may be formed as a tamper-responsive laminate having a series of separate layers, such as an outermost tamper-responsive layer comprising a matrix of, for example, diagonally extending or sinusoidally extending conductive or semiconductive lines printed on a standard, thin, insulating foil. The matrix of lines forms a series of continuous conductors that would be interrupted if attempts were made to penetrate the foil. The lines may be formed, for example, by printing a carbon-loaded polymer thick film (PTF) ink onto the foil and selectively connecting the lines on each side by conductive vias near the edges of the foil.Connections between the leads and a data link card's housing monitoring device can be provided, for example, via one or more ribbon cables. The ribbon cable itself can, if desired, be formed from lines of conductive ink printed on an extension of the film. Connections between the matrix and the ribbon cable can be made via connectors formed on an edge of the film. As mentioned, the laminate can be wrapped around the electronic assembly housing to define the tamper-responsive sensor 120 surrounding the housing 110.

[0016] In one or more implementations, the various elements of the laminate may be adhered to and wrapped around the housing 110 in a manner similar to wrapping a package in gift wrap, defining the tamper-responsive sensor shape 120. The assembly may be placed in a mold, which is then filled with, for example, cold-cast polyurethane, and the polyurethane may be cured and hardened to form an encapsulation 130. The encapsulation, in one or more embodiments, may completely surround the tamper-responsive sensor 120 and the housing 110, thereby forming a complete environmental seal that protects the interior of the housing. The cured polyurethane is resilient and increases the robustness of the electronic component during normal use.Optionally, an outer thermally conductive housing 140 may be provided over the encapsulation 130 to, for example, provide further structural rigidity to the electronic component.

[0017] It should be noted that as an improvement within a sealed electronic component such as the one in Fig. 1 and described above, structures and methods for facilitating heat transfer from one or more electronic components disposed therein to the outside may be provided through the housing and any other layers of the electronic component.

[0018] Fig. 2 illustrates in detail one embodiment of a typical tamper-evident electronic package 200. The electronic package 200 is defined, for example, by a lower metal half-shell 202 and an upper metal half-shell 204. Outer surfaces of the lower metal half-shell 202 and the upper metal half-shell 204 may be provided with spacers 206, with an electronic assembly 208 resting on the spacers 206 defined in the lower metal half-shell 202. The electronic assembly 208 may, for example, include a printed circuit board 210, with electronic components 212 electrically connected via conductors (not shown) defined in or on the printed circuit board 210.

[0019] Hollow spacers 213 may be placed beneath indentations 206 in the upper metal half-shell 204, and rivets 214 may be provided extending through openings in the indentations 206, through the hollow spacers 213, and through openings in the printed circuit board 210 to the lower metal half-shell 202 such that the electronic assembly 208 is securely fixed within the housing formed by the lower and upper metal half-shells 202, 204. A safety net or tamper-evident sensor 216 is wrapped around the top, bottom, and four sides of the housing formed by the upper and lower metal half-shells 202, 204. As illustrated, in one or more embodiments, the upper metal half-shell 204 may include an opening through which a bus 220 extends.One end of the bus 220 may be connected to conductors (not shown) on a printed circuit board 210, and the other end may be connected to conductors (not shown) on a printed circuit board 222. Because the bus 220 passes through the opening, the bus extends between an inner edge region 223 of the safety net 216 and an overlapping outer edge region 224 of the safety net 216. A composite of wires 226, in one embodiment, connects the safety net 216 to conductors on the printed circuit board 210. Circuits on the printed circuit board 210 are responsive to a break or open circuit in the safety sensor array 216, in which case an alarm signal may be issued via the bus 220 and, furthermore, encryption / decryption keys stored within the electronic assembly 208 may be erased.

[0020] In one or more implementations, a liquid polyurethane resin may be applied to the safety net 216 and cured. An outer thermally conductive housing 228, such as a copper housing, may be filled with liquid polyurethane resin, with the electronic assembly and an inner housing and safety net suspended therein. Upon curing of the resin, the electronic assembly, the inner housing, and the safety net may be integrated into a polyurethane block or encapsulation 230, as shown. The housing 228 is mounted on the printed circuit board 222, which may be accomplished, for example, using pins 240 that extend through slots in the printed circuit board 222 and terminate in flanges 242, which are subsequently bent out of alignment with the slots.The bus 220 can be connected via the printed circuit board 222 to connectors 244 located, for example, along an edge of the printed circuit board 222.

[0021] If tamper-evident encapsulation is considered, the electronic component must maintain defined tamper-evident requirements such as those outlined in the National Institutes of Standards and Technology (NIST) publication FIPS 140-2, a U.S. government computer security standard used for the approval of cryptographic modules. NIST FIPS 140-2 defines four security levels, referred to as Level 1 through Level 4, with Security Level 1 providing the lowest level of security and Security Level 4 providing the highest level of security. At Security Level 4, physical security mechanisms are provided to create a complete protective enclosure around the cryptographic module with the intent of detecting and responding to any unauthorized attempt at physical access.An intrusion into the encryption module's enclosure from any direction is detected with a very high probability, resulting in the immediate zeroing of all Critical Security Parameters (CSPs) in plaintext. Security Level 4 encryption modules are suitable for operation in physically unprotected environments. Security Level 4 also protects an encryption module from security compromises due to environmental conditions or fluctuations in voltage or temperature outside the module's normal operating ranges. Intentional deviations beyond the normal operating ranges can be exploited by an attacker to counteract the encryption module's security measures.The encryption module is required to either include special environmental protection features designed to detect fluctuations and zero critical security parameters, or to undergo rigorous environmental fault testing to provide reasonable assurance that the module will not be affected by fluctuations outside its normal operating range in a manner that may compromise the module's security.

[0022] To meet the demands of ever-improving intrusion protection technology and the higher-performance encryption / decryption functions provided, improvements to the tamper-evident, tamper-resistant electronic package for the subject electronic assembly are desired. Numerous improvements are described herein, for example, tamper-responsive assemblies and tamper-responsive sensors. It should be noted that the numerous inventive aspects described herein may be used individually or in any desired combination. Furthermore, in one or more implementations, the improvements to a tamper-resistant electronic package described herein may be provided to operate within limited space constraints for existing devices.For example, one or more of the concepts described can be designed to work with the size limitations of the Peripheral Component Interconnect Express (PCIe) and the constraints resulting from encapsulation, for example, in an isolating encapsulation.

[0023] Therefore, in the following, with reference to Fig. 3A to 21C describe various approaches and / or improvements for creating a secure space for accommodating one or more electronic components, such as one or more encryption and / or decryption modules and associated components of a data transmission card or other electronic assembly.

[0024] Fig. 3A illustrates a portion of one embodiment of a tamper-responsive layer 305 (or a laser or penetration-responsive layer) of a tamper-responsive sensor 300 or a security sensor, as discussed herein. Fig. 3A, the tamper-responsive layer 305 includes circuit lines or traces 301 provided on one or both opposite sides of a flexible layer 302, which in one or more embodiments may be a flexible insulating layer or film. Fig. 3A illustrates circuit lines 301, for example, on one side of the flexible layer 302, with the traces on the opposite side of the film, for example, having the same pattern but (in one or more embodiments) offset to lie between circuit lines 301 directly beneath gaps 303. As described below, the circuit lines on one side of the flexible layer may have a line width W l and have a grid spacing or a distance between lines W ssuch that penetration of layer 305 at any location results in damage to at least one of the circuit traces 301. In one or more implementations, the circuit traces may be electrically connected in series or parallel to define one or more conductors that may be electrically connected in a network to a package monitor that monitors the electrical resistance of the traces, as described herein. Detection of an increase or other change in electrical resistance caused by cutting or damaging one of the traces causes data within the encryption and / or decryption module to be erased.Providing conductive lines 301 in a pattern, such as a sinusoidal pattern, may advantageously make it difficult to breach a tamper-responsive layer 305 without detection. In this regard, it should be noted that the conductive lines 301 could be provided in any desired pattern. For example, in an alternative implementation, conductive lines 301 could be provided as parallel, straight conductive lines, if desired, and the pattern or orientation of the pattern may vary between sides of a layer and / or between layers.

[0025] As mentioned, as intrusion technology advances, it must continue to improve to maintain its leadership. In one or more implementations, the tamper-responsive sensor 300 summarized above may be Fig. 3A over an outer surface of an electronics housing such as one described above in connection with Fig. 1 & 2. As further described herein, the tamper-responsive sensor may alternatively cover or line an interior surface of an electronics housing to provide a secure space around at least one electronic component to be protected. Numerous improvements to the tamper-responsive sensor itself are described below.

[0026] In one or more aspects, a tamper-responsive sensor 300 is disclosed herein whose circuit lines 301 have reduced line widths W lof, for example, 200 µm or less, such as less than or equal to 100 µm, or more particularly in the range of 30 to 70 µm. In contrast, conventional web widths are usually on the order of 350 µm or more. Reducing the width W l The spacing width W is also determined according to the circuit lines. s 303 between the lines to less than or equal to 200 µm, such as less than or equal to 100 µm or, for example, to a range of 30 to 70 µm. Advantageously, the width and pitch of the circuit lines by reducing the line width W l and the distance W sThe circuit lines 301 between the lines within the tamper-sensitive sensor 300 are of the same order of magnitude as the smallest currently available intrusion instruments, and therefore, any intrusion attempt will necessarily result in the removal of a sufficient amount of one or more circuit lines to cause a change in electrical resistance, thereby detecting the tampering intrusion. It should be noted that if the circuit lines are designed with the smaller dimensions disclosed herein, any cutting or damage to the smaller-sized circuit line will also be more likely to be detected, that is, due to a larger change in electrical resistance. For example, if a 100 µm wide line is cut 50% during an intrusion attempt, the remaining available line width for conducting current is reduced to 50 µm.Compared to, for example, a 50% reduction in a more conventional line width of 350 µm to approximately 175 µm, this change is more likely to result in a detectable change in electrical resistance. The smaller the width of the conductive circuit line, the more likely it is that tampering with that line will be detected.

[0027] It should also be noted that a variety of materials can be advantageously used to form the circuit lines. For example, the circuit lines can be printed from a conductive ink (such as a carbon-loaded conductive ink) on one or both opposite sides of one or more of the flexible layers 302 in a stack of such layers. Alternatively, a metal or metal alloy could be used to form the circuit lines, for example, copper, silver, silver-carbon, or nickel-phosphorus (NiP), or Omega-Ply. ®, offered by Omega Technologies, Inc. of Culver City, California (USA), or Ticer™, offered by Ticer Technologies, Chandler, Arizona (USA). It should be noted that the process used to form the thin circuit lines or traces on the scale described herein depends in part on the choice of material used for the circuit lines. For example, when fabricating copper circuit lines, additive processing such as plating copper traces or subtractive processing such as etching away unwanted copper between trace lines may be used. Furthermore, for example, when using a conductive ink as the material for the circuit lines, thin circuit lines on the scale disclosed herein may be achieved by focusing on the rheological properties of the conductive ink formulation.Furthermore, instead of using simple pneumatics to force the conductive ink through an opening in a stencil with a squeegee, the screen emulsion can be very thin (e.g., 150 to 200 µm), and a squeegee angle can be used to shear the ink to achieve tearing of the conductive ink, rather than pumping the conductive ink through the screen openings.It should be noted that the screen for printing thin line widths as described herein may, in a specific embodiment, have the following characteristics: a thin polyester thread for warp and weft having a size of on the order of 75 micrometers; a thread count between 250 and 320 threads per inch; a mesh size of, for example, 150 micrometers; an open area between threads that is at least 1.5 to 2.0 times the particle size of the conductive ink; and to maintain dimensional stability of the print, screen bounce due to screen tension during a squeegee pass is kept to a minimum.

[0028] In one or more implementations, the circuit lines 301 of the tamper-responsive sensor 300 are electrically connected to define one or more resistive networks. Furthermore, the circuit lines can be configured by selecting the line material, the line width W l and the cable length L l include one or more resistive circuit lines to provide a desired electrical resistance per line. As an example, a "resistive circuit line" as used herein may include a line with a continuous electrical resistance of 1,000 ohms or more. In a specific example, a circuit line width of 50 µm may be used with a circuit line thickness of 10 µm, and the line length L land the material must be selected to achieve the desired electrical resistance. With the dimensions described, good electrical conductors such as copper or silver can also be used, and due to the thin dimensions mentioned above, a resistance network can still be formed. Alternatively, materials such as conductive ink or the aforementioned Omega-Ply ® or Ticer™ to define resistive circuit lines.

[0029] In another aspect, the thickness of the flexible layer 302 itself can be further reduced compared to a typical polyester layer by selecting a crystalline polymer to form the flexible layer or flexible substrate. As an example, the crystalline polymer could comprise polyvinylidene difluoride (PVDF) or Kapton, or another crystalline polymer material. Advantageously, using a crystalline polymer as the substrate film can reduce the thickness of the flexible layer 302 to, for example, a thickness of 2 mils compared to a more conventional amorphous polymer layer of approximately 8 mils. The thickness of a crystalline polymer can be significantly reduced while still maintaining the structural integrity of the flexible substrate, advantageously enabling significantly greater folding and greater reliability of the sensor after folding.It should be noted that the radius of any bend or curvature of the sensor is necessarily limited by the thickness of the layer containing the sensor. Thus, by reducing the thickness of the flexible layer to, for example, 2 mils in a stack of four tamper-responsive layers, the stack thickness of approximately 30 mils for a typical polyester film can be reduced to 10 mils or less by using crystalline polymer films.

[0030] As noted, the circuit lines 301 forming the at least one resistive network may be disposed on either the first side or the second side of the opposite sides of the flexible layer(s) 302 within the tamper-responsive sensor 300, or on both the first and second sides. One embodiment of this is described in Fig. 3B, illustrating circuit lines 301 on both opposite sides of the flexible layer 302. In this example, the circuit lines 301 on the opposite sides of the tamper-responsive sensor 302 may each have line widths W l of less than or equal to 200 µm, and these line widths may be the same or different. Furthermore, the pitch width W sbetween adjacent lines of the circuit lines 301 may also be less than or equal to 200 µm and may also be the same or different. In particular, the circuit lines may have different line widths on the two different sides of the tamper-respondent layer, and the spacing widths between lines may also be different. For example, a first side of the tamper-respondent layer may have circuit line widths and spacings between lines of approximately 50 micrometers, whereas the second side of the tamper-respondent layer may have circuit lines and spacings between lines of 70 micrometers. By providing such different widths, intrusion by the sensor is potentially made more difficult.Circuit lines 301 on opposite sides of the flexible layer 302 may also have the same or different patterns and the same or different orientations. If they have the same pattern, the circuit lines may be offset, as noted above, so that the circuit lines on one side are aligned with spaces between circuit lines on the other side.

[0031] As in Fig. As illustrated in Figure 3C, the tamper-sensitive sensor 300 may include a stack of tamper-sensitive layers 305 secured together with an adhesive 311, such as a double-sided adhesive film. The process may be repeated to obtain any desired number of tamper-sensitive layers, or more specifically, any desired number of layers of circuit lines 301 within the tamper-sensitive sensor to obtain a desired intrusion-protection sensor.

[0032] In Fig. 3D illustrates an alternative tamper-responsive sensor 300' wherein a plurality of flexible layers 302 having circuit lines are secured together with an adhesive 311, and, as an example, circuit lines are provided on one or both sides of each flexible layer. In this example, a first flexible layer 302 includes first circuit lines 301, and a second flexible layer 302 includes second circuit lines 301'. In one or more implementations, the first circuit lines may have a first line width W l and the second circuit lines may have a second line width W lwherein the first line width of the first circuit lines 301 differs from the second line with the second circuit lines 301'. For example, the width of the first circuit lines may be 50 µm, and the width of the second circuit lines may be 45 µm. It should be noted that in this example, any desired combination of circuit line widths may be used, it being understood that the circuit line widths may differ between at least two of the layers. In addition, the first circuit lines 301 of the first flexible layer may have a first pitch width W s between lines, and the second circuit lines 301' of the second flexible layer may have a second pitch width W sbetween lines, wherein the first spacing width of the first circuit lines may differ from the second spacing width of the second circuit lines between lines. Note that this concept also applies to circuit lines on only one side of the flexible layer 302, where two or more of the flexible layers in the stack defining the tamper-respondent sensor may have different circuit line widths and / or different spacing widths between lines. This concept can be extended to any number of tamper-respondent layers within the tamper-respondent sensor to provide a desired level of tamper protection.

[0033] Additionally or alternatively, the first circuit lines 301 of the first flexible layer may be formed from a first material, and the second circuit lines 301' of the second flexible layer may be formed from a second material, wherein the first material of the first circuit lines 301 may be different from the second material of the second circuit lines 301'. For example, the first circuit lines 301 may be formed from conductive ink, and the second circuit lines 301' may be formed from a metal such as copper. By providing the tamper-responsive sensor 300 with at least some of the circuit lines formed from a metal material such as copper, improved tamper detection may be achieved.

[0034] For example, a burglary tool penetrating one or more layers of metal circuit lines 301' could generate debris that is dispersed during the burglary attempt and causes one or more other tamper-responsive layers within the tamper-responsive sensor 300' to be shorted or otherwise damaged. If desired, more than two materials may be used in more than one layer of circuit lines within the tamper-responsive sensor.

[0035] Fig. 3E illustrates another embodiment of a tamper-evident assembly 300. In this implementation, a plurality of tamper-evident layers 305 are attached to another flexible layer 320 in a stack using, for example, one or more layers of an adhesive film 311. In one or more implementations, the another flexible layer 320 could comprise a deformable metal foil. In the illustrated example, the deformable metal foil is disposed between two tamper-evident layers 305 and is thus disposed between two layers of circuit lines 301 on the different tamper-evident layers 305. For example, the deformable metal foil 320 could comprise a sheet of copper or a copper alloy.By providing a thin, deformable metal foil 320 having a thickness on the order of, for example, 0.001", an attempt to penetrate the tamper-responsive sensor 300 would inevitably penetrate the deformable metal foil 320, generating debris carried along by the burglary tool or drill. This metal debris would facilitate detection of the burglary attempt by potentially shorting or otherwise damaging one or more of the tamper-responsive layers 305 within the tamper-responsive sensor 300. As a variation, the deformable metal foil 320 could be applied directly to one side of a flexible layer 302, with the opposite side having circuit lines that would form the at least one resistive network.It should be noted that a similar concept applies when one or more of the layers of circuit lines 301 are formed from metal circuit lines, such as copper or silver, and other layers of circuit lines 301 are formed from, for example, conductive ink. In such embodiments, cutting one or more metal lines would generate metal residue that would be carried by the intrusion tool and ultimately interact with one or more other circuit lines of the tamper-responsive electronic circuit structure, increasing the likelihood of damage and, consequently, detection of the intrusion attempt.

[0036] Based on the description provided herein, those skilled in the art will understand that the above-mentioned Fig. 3A to 3E may be used with any of a variety of different tamper-responsive assemblies and, if desired, may be preformed in any of the various configurations described below. For example, one or more of the tamper-responsive sensors of Fig. 3A to 3E, in conjunction with an electronics enclosure to at least partially enclose one or more electronic components to be protected, with the tamper-responsive sensor overlying or adhered to an exterior surface of the electronics enclosure. Alternatively, in one or more implementations, the tamper-responsive sensor could be provided to cover or line an interior surface of the electronics enclosure, such as in one or more of the tamper-responsive assemblies described below.

[0037] In contrast to a previous tamper-evident sensor, which may utilize a single substrate of flexible dielectric with circuit lines on either the top or bottom surface or both, tamper-evident sensors are provided herein that, in one or more embodiments, include multiple layers of materials and circuits to provide an improved tamper-resistant, tamper-evident packaging to meet the demands of ever-improving intrusion prevention technology requirements for protecting encryption / decryption functions. Fig. 4A & 4B provide exemplary tamper-responsive sensors comprising stacks of layers, each including at least one shaped, flexible layer, which may be configured, for example, as a corrugated layer of flexible dielectric with circuit lines on one or both sides. Note that a "shaped layer" herein refers to a specially shaped layer, for example, fabricated with curves that extend at least partially out of plane. For example, in a corrugated layer, as shown, the curves may have a vertical component, resulting in a waveform of the shaped layer.

[0038] As in Fig. 4A, a tamper-responsive sensor 400 may, for example, include a first sensor layer 410, a second sensor layer 420, and a third sensor layer 430, with the second sensor layer 420 sandwiched between the first and third sensor layers 410, 430. In this configuration, the second sensor layer 420 includes a molded, flexible layer 401 having opposing first and second sides with circuit lines 402, which may include, for example, circuit lines such as metal lines (e.g., Cu or Au lines), wires, printed conductive ink (e.g., carbon ink), resistive materials, etc., forming at least one resistive network on the first side and / or on the second side of the molded, flexible layer.In one or more embodiments, the circuit lines may comprise narrow pitch circuits, for example, circuit lines with a width in the range of 20 to 50 micrometers and spacings of 20 to 50 micrometers between the circuit lines. In one or more implementations, the shaped, flexible layer comprises at least in part a dielectric material (such as polyimide, Mylar™, Teflon™, etc.), in such an example the layer is referred to as a corrugated layer of flexible dielectric, with the circuit lines at least partially overlying the curvatures of the corrugated layer of the dielectric, as illustrated. Note that in the example of . Fig. 4A shows a cross-section through the tamper-sensitive sensor 400 intersecting multiple layers of circuit lines on the various sensor layers. The wiring patterns of the circuit lines can have any desired configuration. For example, the circuit lines can be arranged orthogonally, angularly, or randomly with respect to adjacent, underlying, or overlying circuit lines of the tamper-sensitive sensor. This possibility applies to all tamper-sensitive sensors disclosed herein in which circuit lines are provided on multiple different surfaces of a tamper-sensitive sensor.As a further variation, each tamper-responsive electronic circuit structure may have a unique circuit line configuration or set of circuit line configurations associated, for example, with a serial number of the provided tamper-responsive electronic circuit structure. Furthermore, any number of sensor layers may be associated with the at least one molded, flexible layer of the tamper-responsive sensor.

[0039] Therefore, in one or more embodiments, the first sensor layer 410 and the third sensor layer 430 may further comprise a flexible layer of material having circuit lines disposed on the first and / or second sides thereof, forming one or more resistive networks. For example, conductive circuit lines may be provided on both the first and second sides of the flexible layers of the first sensor layer 410, the second sensor layer 420, and the third sensor layer 430, such that a vertical cross-section through the stack of layers intersects multiple layers of circuit lines.In this design, by forming the second sensor layer 420 with curvatures, for example, by forming the second layer in a corrugated manner, protection against physical intrusion, such as by a drill, without detection by the resistor network(s) is advantageously improved by making it more difficult to detect the position of the circuit lines defining the resistor networks.

[0040] For example, the second sensor layer 420 may initially comprise a thin, flexible layer of material, for example, a thin, flexible layer having a thickness comparable to the desired minimum radius of bending curvature for the desired corrugation of the second sensor layer. In one or more implementations, the second sensor layer may be corrugated by sourcing a flat, flexible sensor, which is then passed through a set of heated top and bottom rollers, each having intermeshing gears, to create the desired sinusoidal pattern in the sensor layer. One or more outer circuit layers or foils, comprising the circuit lines that form the one or more resistive networks, may then be layered, as desired, onto one or both of the first and second sides of the formed layer to define the formed, flexible layer.In one or more implementations, an adhesive may be used to attach the circuit layers or films comprising the one or more resistive networks to the molded layer. For example, the adhesive could include a PSA, an epoxy, an acrylic, a thermoset, a thermoplastic, an electrically conductive epoxy, a thermally conductive epoxy, etc., one or more of which could also be used to attach the plurality of sensor layers 410, 420, 430 to each other within the stack of layers.

[0041] As in Fig. 4B, a plurality of second corrugated layers 420 of a flexible dielectric with circuit lines may be provided in the stack of layers of the tamper-responsive sensor 400, for example, wherein adjacent corrugated layers of the flexible dielectric are separated by a substantially flat, flexible layer, wherein additional circuit lines may be present defining one or more additional resistive networks. In the illustrated embodiment, adjacent corrugated layers of the flexible dielectric with circuit lines are separated by a sensor layer 425, which in turn may include circuit lines on one or both sides thereof.

[0042] Connections of the tamper-responsive sensors and sensor layers described herein, for example, for monitoring circuits disposed within the associated secure space defined by the tamper-responsive electronic circuit structure, may include input / output contacts or connectors formed on one or more edges of the tamper-responsive sensor (or sensor layer), or one or more ribbon cables extending from the tamper-responsive sensor into the secure space, as would be apparent to one of ordinary skill in the art.

[0043] Fig. 5A & 5B depict another embodiment of a tamper-responsive sensor 500. As illustrated, the tamper-responsive sensor 500 includes at least one molded, flexible layer 510 having opposing first and second surfaces 511, 512. Circuit lines 501 forming at least one resistive network are provided on the first and / or second sides 511, 512 of the molded, flexible layer 510. As noted, the circuit lines may comprise any desired pattern of conductive circuit lines advantageous for a particular tamper-responsive sensor technology and may include multiple sets of circuit lines in different regions or zones of the molded, flexible layer. For example, the circuit lines may be conductive lines such as metal lines (e.g., copper lines), wires, printed conductive ink (e.g., carbon ink), etc.provided on the first and / or second side of the molded, flexible layer 510. As shown in . Fig. 5A, the shaped flexible layer in this embodiment again includes bends 513, with the shaped flexible layer having bends being folded over as a flattened, folded-over layer. Note that the circuit lines 501 forming the at least one resistive network on the first side 511 or the second side 512 of the shaped flexible layer 510 at least partially overlie at least some of the bends 513 such that the circuit lines are wrapped over or within the bends 513 and, in the transverse cross-sectional view, provide multiple layers of circuit lines formed on the same curved surface of the shaped flexible layer.In one or more embodiments, the shaped flexible layer 510 may be a corrugated layer that has been flattened by applying a force in the z-direction of a measured xy shear force, thereby creating a controlled flattening collapse of the multi-dimensional shaped flexible layer 510.

[0044] Fig. 5C to 5H illustrate various examples of a tamper-responsive sensor comprising a stack of layers, wherein one or more of the layers comprises a shaped, flexible layer 510, such as described above in connection with Fig. 5A & 5B. For example, Fig. 5C illustrates a stack of layers including the molded, flexible layer 510, with at least one other layer 520 overlying the first side 511 and / or the second side 512 of the molded, flexible layer 510. In one or more embodiments, the at least one other layer 520 overlying the molded, flexible layer 510 may be or include an opaque layer of material for concealing the position of the circuit lines or a frangible layer of material that shatters upon tampering and facilitates damaging the circuit lines forming the at least one resistive network to assist in detecting the attack on the tamper-responsive sensor.In one or more implementations, the opaque layer of the material may be a dark, non-transparent material that hides what lies beneath, or in one or more embodiments, the opaque material could be a material of the same color as the resistive circuit lines of the underlying layer that hides and camouflages the covered circuit lines.

[0045] In Fig. 5D, a plurality of other layers 521, 522 overlie one or both sides 511, 512 of the shaped, flexible layer 510. In one example, the plurality of other layers may include both a frangible layer 521 and an opaque layer 522 disposed on one side of the shaped, flexible layer 510 or on both sides of the shaped, flexible layer 510.

[0046] In further embodiments, one or more of the other layers may themselves comprise a flexible dielectric material with circuit lines forming at least one other resistive network on the first side or on the second side thereof. Fig. 5E illustrates another layer 520 overlying the second side 512 of the molded, flexible layer 510, and Fig. 5F illustrates another layer 520 overlying the first side 511 and another layer 520 overlying the second side 512 of the molded flexible layer 510.

[0047] Fig. 5G & 5H illustrate additional embodiments of a tamper-evident sensor 500 comprising a stack of layers. In these embodiments, a plurality of molded, flexible layers 510 are provided along with one or more other layers overlying one or more sides 511, 512 of the molded, flexible layers 510. As noted, the one or more other layers may comprise a variety of layers, such as an opaque flexible layer, a frangible layer, or additional flexible layers with circuit lines that form additional resistive networks of the tamper-evident sensor as desired to provide an improved tamper-resistant packaging with tamper evidence for a particular application.

[0048] Fig. 6A to 6G illustrate various embodiments for a tamper-responsive assembly, generally designated 600, in which a secure space is defined for protecting one or more electronic components or an electronic assembly, as discussed herein. Referring to Fig. 6A, a tamper-responsive assembly 600 may include an electronics housing 601, such as a rigid, conductive housing, and a tamper-responsive electronic circuit structure 602 associated with the electronics housing 601. As shown, the tamper-responsive electronic circuit structure 602 includes a tamper-responsive sensor 605.In one or more implementations, the tamper-responsive sensor 605 includes at least one shaped flexible layer having opposing first and second sides, circuit lines forming at least one resistive network disposed on the first and / or second sides, and shaped bends provided within the shaped flexible layer, wherein the circuit lines at least partially overlie the bends of the shaped flexible layer, such as described above in connection with the exemplary embodiments of FIG. Fig. 4A to 5H.

[0049] When implementing Fig. 6A, a single, continuous, tamper-evident sensor 605 is provided that is wrapped around the electronics housing 601 and includes overlaps 606 where the ends join along the electronics housing 601. For example, the single, continuous, tamper-evident sensor 605 could be wrapped around the electronics housing 601 in any manner similar to wrapping a gift. By way of example only, the electronics housing 601 could be a 6-sided metal container sized to contain the electronics to be protected. Further, in this configuration, the tamper-evident sensor 605 configured as described above can be used in a package of an electronic assembly, as initially described in connection with Fig. 1 & 2 described.

[0050] Fig. 6B through 6G illustrate further embodiments of the tamper-responsive assembly 600. In one or more of these embodiments, multiple discrete tamper-responsive sensors 610, 611, 612 are illustrated. For example, each tamper-responsive sensor may include one or more molded, flexible layers with circuit lines extending at least partially across the curves of the molded, flexible layers, as described herein.

[0051] In the example of Fig. 6B, an upper tamper-responsive sensor 610 and a lower tamper-responsive sensor 611 are provided, respectively overlying the upper and lower major surfaces of the electronics housing 601. Furthermore, a sidewall-located tamper-responsive sensor 612 wraps around the edge of the electronics housing 601 and, in this example, has a sufficient width to wrap over the upper tamper-responsive sensor 610 and the lower tamper-responsive sensor 611, thus overlapping 606 them, as illustrated. The extent of the overlap 606 can be adjusted as desired to prevent attack by the tamper-responsive electronic circuitry at the edges where the various tamper-responsive sensors 610, 611, 612 meet.

[0052] Fig. Figure 6C is a plan view of one embodiment of the assembly of Fig. 6B from above, wherein the tamper-responsive sensor 612 is shown wrapped around the upper tamper-responsive sensor 610 provided over the upper major surface of the electronics housing 601. A corresponding wrap of the tamper-responsive sensor 612 around the lower tamper-responsive sensor may also be employed. In this configuration, note the provision of diagonal folds 615 at the corners where the tamper-responsive sensor 612 overlaps the upper tamper-responsive sensor 610. This example of Fig. 6C for an overlap and foldover is provided merely as an example, and other overlap and foldover configurations may be employed without departing from the scope of the claims presented herewith. In this six-sided package example, the sidewall tamper-evident sensor 612 is a separate sensor that wraps around the perimeter of the electronic assembly package 601 and overlaps the upper and lower tamper-evident sensors 610 and 611, respectively.

[0053] Fig. 6D represents a variant of the tamper-responsive assembly 600 from Fig. 6B, wherein the upper tamper-responsive sensor 610 and the lower tamper-responsive sensor 611 extend beyond the top and bottom surfaces of the electronics housing 601, respectively, and are folded over to overlap the sidewall tamper-responsive sensor 612 provided along the edge or perimeter of the electronics housing 601.

[0054] Fig. 6E & 6F illustrate alternative embodiments of the upper tamper-responsive sensor 610 for use in various embodiments of a tamper-responsive assembly, including, for example, an assembly as shown in Fig. 6D, wherein the upper tamper-responsive sensor 610 is wrapped around an edge of the housing and the sidewall tamper-responsive sensor 612 is sized to the width of the edge or sidewall of the electronics housing 601. In the embodiment of the upper tamper-responsive sensor 610 of Fig. 6E, corner recesses or indentations 607 are made to facilitate folding of the illustrated edge flaps over the tamper-responsive sensor 612 located on the side wall, such as in Fig. 6D. If desired, additional tamper-evident corner sensors (not shown) can be used as filler over the corners where the edge flaps meet at the corners of the assembly package to provide an even more tamper-resistant enclosure with tamper evidence along the respective edges of the edge flaps. It should be noted that in this configuration, the sidewall tamper-evident sensor 612 ( Fig. 6D) is completely wrapped around the electronics housing 601 and thus necessarily provides coverage at the edges where the edge flaps meet.

[0055] As a variant, Fig. 6F illustrates an upper tamper-responsive sensor 610 having corner cutouts 608 reduced to slots or channels to define tabs from the edge flaps at the corners of the edge flaps to allow further folding along the edge or sidewall of the electronics enclosure 601. That is, the further tabs can be folded across the edge between adjacent edge flaps at the corners when the upper tamper-responsive sensor 610 is folded over the sidewall tamper-responsive sensor 612, such as in Fig. 6D illustrates.

[0056] It should be noted that in the embodiments of Fig. 6A to 6D, the tamper-responsive sensors may have respective input / output (I / O) wiring extending from one or more ends thereof into a region below an overlap region of two of the tamper-responsive sensors, the I / O wiring extending into the secure space of the device to electrically connect to the tamper-detection circuitry. For example, the resistor networks within the tamper-responsive sensors may be electrically connected to circuitry within the secure space for monitoring the networks. The monitoring circuitry may include various bridging and / or comparator circuits and utilize conventional electrical connection within the secure space of the electronics package 601.Any number of connection designs can be used, for example, depending on the number and properties of the resistor network provided within the tamper-responsive sensors.

[0057] In the embodiment of Fig. 6G is the tamper-sensitive sensor 612 ( Fig. 6D) has been removed, and the size of the upper and lower tamper-responsive sensors 610, 611 is expanded to allow the upper and lower tamper-responsive sensors 610, 611 to overlap along the edge or side wall of the electronics housing 601 where they are folded over, as shown.

[0058] It should be noted that despite the representation in Fig. 6A to 6G could be implemented as flattened, folded layers of one or more of the respective illustrated tamper-responsive sensors in other ways. For example, one or more of the top, bottom, or sidewall tamper-responsive sensors in the illustrated examples could be other shaped, flexible layers as described in Fig. 4A to 5H, or other unformed, flexible layers with circuit lines forming resistive networks on one or both opposite sides of the flexible layer(s). Further examples of tamper-responsive sensors are described below in connection with Fig. 7A to 7C.

[0059] Fig. 7A to 7C illustrate another embodiment of a tamper-responsive circuit structure having one or more interwoven multiple sensor layers. In particular, Fig. 7A, a first tamper-responsive sensor 700 is illustrated as including at least one first layer 701, such as a flexible dielectric layer, having opposing first and second sides. First circuit lines 702 are provided on the first side and / or the second side of the at least one first layer 701 to form at least one first resistive network. A plurality of slots 703 are provided in the at least one first layer 701, with the first circuit lines recessed a predetermined minimum distance, for example, 2 to 10 mils, from the plurality of slots 703.

[0060] As in Fig. 7B, the tamper-responsive electronic circuit structure may include an interwoven multi-sensor layer 720 defined by interweaving the first tamper-responsive sensor 700 with a second tamper-responsive sensor 710, which, in one or more embodiments, is constructed similarly to the first tamper-responsive sensor 700. In particular, the second tamper-responsive sensor 710 may include at least one layer, such as a flexible layer, having opposing first and second sides, and second circuit lines disposed on the first and / or second sides of the at least one second layer, defining at least one second resistive network.It should be noted that the at least one first resistor network and at least one second resistor network may be identically or differently structured resistor networks. In one or more implementations, for example, the width of the circuit lines or traces in the different resistor networks, as well as the pitch between the lines, may vary. By providing slots within the first tamper-responsive sensor 700 and the second tamper-responsive sensor 710, the resulting fingers of the first and second tamper-responsive sensors may be interwoven to define an interwoven multi-sensor layer 720 having a checkerboard pattern, such as shown in FIG. Fig. 7B illustrates.

[0061] As in Fig. 7C, an improved tamper-evident electronic circuit structure can be achieved by stacking two interwoven multi-sensor layers 720 in which the slit lines, and in particular the intersections of the slit lines, are offset to provide a more tamper-resistant electronic structure with tamper evidence. For example, the interwoven multi-sensor layer 720 of Fig. 7B may be a first interwoven multi-sensor layer, and the circuit structure may include a second interwoven multi-sensor structure overlying the first interwoven sensor layer, wherein the second interwoven multi-sensor layer is arranged in a manner as described, for example, above in connection with Fig. 7A & 7B, formed from additional discrete, tamper-responsive sensors. In this configuration, the second interwoven multi-sensor layer 720' may be constructed such that the slot intersections between the discrete, tamper-responsive sensors woven into this layer are not aligned with those of the first interwoven multi-sensor layer 720 when stacked.For example, the slots in the second interwoven multi-sensor layer 720' could be spaced differently than those in the first interwoven multi-sensor layer 720, such that the intersections of the slots in the second interwoven multi-sensor layer are offset from those in the first interwoven multi-sensor layer, or the second interwoven multi-sensor layer 720' could be constructed consistent with the first interwoven multi-sensor layer 702 but slightly offset from the first interwoven multi-sensor layer when stacked. Advantageously, if desired, in one or more implementations, one or more interwoven multi-sensor layers 720, 720' can be employed as one of the top, bottom, or sidewall tamper-responsive sensors described above in connection with. Fig. 6A to 6G have been described.

[0062] As another example, Fig. 8A & 8B illustrate an embodiment of another tamper-responsive assembly or tamper-resistant electronic component 800 including electronic circuitry 815.

[0063] With reference in its entirety to Fig. 8A & 8B, the electronic circuit 815 includes a multilayer circuit board 810 incorporating a tamper-responsive sensor 811, thereby facilitating the definition of a portion of a secure space 801 associated with the multilayer circuit board 810 that extends into the multilayer circuit board 810. In particular, the secure space 801 in the embodiment of Fig. 8A & 8B partially within the multilayer circuit board 810 and partially above the multilayer circuit board 810. One or more electronic components 802 are mounted on the multilayer circuit board 810 within the secure space 801 and may include, for example, one or more encryption modules and / or decryption modules and associated components, wherein the tamper-evident electronic component comprises a data transmission card of a computer system in one or more embodiments.

[0064] The tamper-evident electronic package 800 further includes a housing 820, such as a socket-like housing, which is attached to the multilayer circuit board 810, for example, within a through-going groove (or trench) 812 formed within a top surface of the multilayer circuit board 810. In one or more embodiments, the housing 820 may comprise a thermally conductive material and act as a heat sink to facilitate cooling of the one or more electronic components 802 within the secure space. A safety net or tamper-responsive sensor 821, such as the tamper-responsive sensors described above, may be provided. Fig. 4A through 7C may be bonded to the housing 820, for example, by wrapping it around the inner surface of the housing 820 in a manner that facilitates defining the secure space 801 along with the tamper-evident sensor 811 integrated into the multilayer circuit board 810. In one or more implementations, the tamper-evident sensor 821 extends down into the through-groove 812 in the multilayer circuit board 810 and may, for example, even be partially or completely wrapped around the bottom edge of the housing 820 within the through-groove 812 to provide enhanced tamper detection where the housing 820 is bonded to the multilayer circuit board 810.In one or more implementations, the housing 820 may be securely attached to the multilayer printed circuit board 810 using, for example, a bonding material such as an epoxy or other adhesive.

[0065] As in Fig. 8B, one or more vias 813 for external circuit connection may be provided within the multilayer printed circuit board 810 to provide electrical connection to the one or more electronic components 802 ( Fig. 8A) within the secure space 801. These one or more external circuit connection vias 813 may provide electrical connection to one or more external signal lines or planes (not shown) integrated into the multilayer circuit board 810 and extending, for example, into (or below) a secure lower region of the secure space 801, as further explained below. Electrical connections to or from the secure space 801 may be provided by connecting to such external signal lines or planes within the multilayer circuit board 810.

[0066] As mentioned with reference to Fig. 8A & 8B, the secure space 801 defined in association with the multilayer printed circuit board 810 may be sized to accommodate electronic components 802 to be protected and configured to extend into the multilayer printed circuit board 810. In one or more implementations, the multilayer printed circuit board 810 includes an electrical connection within the secure space 801 defined in the board, for example, for electrically connecting the multiple tamper-evident layers of the integrated tamper-evident sensor 811 to associated monitoring circuitry also disposed within the secure space 801.

[0067] It should be noted that the Fig. 8A & 8B is presented merely as an example. In one or more implementations, the electronic circuit may include a plurality of multilayer circuit boards, each having a tamper-responsive sensor integrated into the multilayer circuit board with a corresponding connector located within a secure space defined between two adjacent multilayer circuit boards that interconnects selected wiring of the multilayer circuit boards. In such an implementation, the overlying multilayer circuit board could be hollowed out to accommodate, for example, the connector and / or one or more other electronic components between the multilayer circuit boards. Furthermore, other configurations of the housing 820 and / or other approaches to interconnecting the housing 820 and the multilayer circuit board 810 may be employed.

[0068] As another example, Fig. 9 illustrates a partial cross-sectional elevation view of one embodiment of the multilayer printed circuit board 810 and the housing 820. In this configuration, the integrated tamper-evident sensor includes multiple tamper-evident layers, including, for example, at least one tamper-evident underlay (or base) layer 900 and at least one tamper-evident frame 901. In the illustrated example, two tamper-evident underlay layers 900 and two tamper-evident frames 901 are illustrated merely by way of example. The lowermost tamper-evident underlay layer 900 may be a continuous sensing or detection layer that extends entirely beneath the secure space defined within the multilayer printed circuit board 810.One or both of the tamper-evident underlay layers 900 below the secure space 801 may be divided into multiple circuit regions, as discussed below. Within each tamper-evident underlay layer, or more precisely within each circuit region of each tamper-evident underlay layer, multiple circuits or conductive traces are provided in any desired configuration, such as that described above in connection with . Fig. 3. Furthermore, the conductive paths within the tamper-sensitive layers can be implemented, for example, as a resistive layer, to which parallel circuits are difficult to connect, as further explained below.

[0069] As illustrated, one or more external signal lines or planes 905 penetrate the secure space 801 between, in this embodiment, two tamper-evident underlay layers 900 and then electrically connect up into the secure space 801 through one or more conductive vias arranged in any desired location and pattern. In the illustrated configuration, the one or more tamper-evident frames 901 are disposed at least within the area defined by the through-groove 812 that receives the bottom of the housing 820. Together with the security sensor 821 associated with the housing 820, the tamper-evident frames 901 define the secure space 801 where it extends partially into the multilayer printed circuit board 810.Since the secure space 801 is at least partially defined within the multilayer printed circuit board 810, the one or more external signal lines 905 can be safely connected to the one or more electronic components 802 (. Fig. 8A) mounted on the multilayer printed circuit board 810 within the secure compartment 801. Furthermore, the secure compartment 801 may accommodate electrical connection of the conductive traces of the multiple tamper-sensitive layers to one another, for example, via suitable monitoring circuits.

[0070] Additional security may be provided by extending the tamper-evident underlay layers 900 (and, if desired, the tamper-evident frame 901) outward beyond the through-groove 812 that receives the housing 820. In this way, an attack at the interface between the housing 820 and the multilayer printed circuit board 810 may be made more difficult because the attack would require removing the tamper-evident underlay layers 900, the lower edge of the tamper-evident sensor 821 associated with the housing 820, and the tamper-evident frames 901 of the integrated tamper-evident sensor.

[0071] Variants of the multilayer printed circuit board 810 from Fig. 8A are possible. For example, in this embodiment, the integrated tamper-evident sensor includes a plurality of tamper-evident backing layers 900 and a plurality of tamper-evident frames 901, as described above, and a three-plate structure having one or more external signal lines or layers disposed between an upper ground plane and a lower ground plane. This configuration would facilitate high-speed transmission of signals into and out of the secure space, and in particular, to and from the one or more electronic components located within the secure space.

[0072] It should also be noted that after the secure space has been defined within the multilayer printed circuit board 810, conductive vias within the secure space between layers of the multilayer printed circuit board 810 can be either aligned or staggered as desired, depending on the implementation. For example, aligning conductive vias may facilitate providing a shortest connection path, whereas staggering conductive vias between layers may further enhance the security of the tamper-resistant electronic device by making it more difficult to attack the secure space through or around one or more tamper-responsive layers of the multiple tamper-responsive layers.

[0073] The tamper-sensitive layers of the integrated tamper-sensitive sensor formed within the multilayer printed circuit board of the electronic circuit or electronic package may include multiple conductive traces or lines formed, for example, between respective sets of input and output contacts or vias at the trace connection locations. Any number of conductive traces or circuits may be employed in defining a tamper-sensitive layer or a tamper-sensitive circuit region within a tamper-sensitive layer. For example, 4, 6, 8, etc., conductive traces may be formed in parallel (or otherwise) within a particular tamper-sensitive layer or circuit region between the respective sets of input and output contacts to these conductive traces.

[0074] In one or more implementations, the multilayer circuit board may be a multilayer wiring board or a printed circuit board formed, for example, by building up the multiple layers on the board. Fig. 10 illustrates an embodiment for forming and patterning a tamper-responsive layer within such a multilayer printed circuit board.

[0075] As in Fig. 10, in one or more implementations, a tamper-evident layer, such as a tamper-evident backing layer or a tamper-evident frame disclosed herein, may be formed by providing a material stack comprising, at least in part, a structural layer 1001, such as a prepreg (or pre-impregnated) material layer, a sheet material layer 1002 used to define the desired trace patterns, and an overlying layer 1003 of a conductive material to be patterned to define conductive contacts or vias that electrically connect the pattern of traces formed within the sheet material layer 1002, for example, at trace termination locations.In one or more implementations, the trace material layer 1002 may comprise nickel-phosphorus (NiP), and the overlying conductive layer 1003 may comprise copper. It should be noted that these materials are provided merely as examples, and that other trace and / or conductive materials may be used in the structure 1000.

[0076] A first photoresist 1004 is provided over the structure 1000 and patterned with one or more openings 1005 through which the overlying conductive layer 1003 can be etched. Depending on the materials and etching processes employed, a second etching process may be desired to remove portions of the trace material layer 1002 to define the conductive traces of the respective tamper-responsive layer. Subsequently, a first photoresist 1004 can be removed, and a second photoresist 1004' is provided over the structural elements of the conductive layer 1003 that are to remain, such as the input and output contacts.Subsequently, exposed portions of the conductive layer 1003 are etched, and the second photoresist 1004' may be removed, with each opening in the layer filled with, for example, an adhesive (or a prepreg), and a next buildup layer is provided, as shown. Note that in this implementation, most of the overlying conductive layer 1003 is etched away, leaving only the conductive contacts or vias where desired, for example, at the termination locations of the traces formed within the layer by patterning the trace material layer 1002. Note that any of a variety of materials may be used to form the conductive lines or traces within a tamper-responsive layer.Nickel-phosphorus (NiP) is particularly advantageous as a material because it is resistant to contact with solder or the use of a conductive adhesive to bond it, making it difficult to bridge from one circuit or track to the next during an attempt to penetrate the protected, secure space of the electronic circuit. Other materials that could be used include OhmegaPly. ® , offered by Ohmega Technologies, Inc., of Culver City, California (USA), or Ticer™, offered by Ticer Technologies of Chandler, Arizona (USA).

[0077] The traces or circuits within all tamper-sensitive layers, and in particular the tamper-sensitive circuit regions of the integrated tamper-sensitive sensor together with the tamper-sensitive sensor 821, may be electrically connected to monitoring or comparison circuits provided, for example, within the secure space 801 of the multilayer printed circuit board 810. The monitoring circuits may include various bridging or comparison circuits and a conventional electrical connection to a printed wiring board within the secure space 801, for example, located within the secure space defined by the tamper-sensitive frames 901 ( Fig. 9) and the manipulation-responsive backing layers are defined.

[0078] It should be noted that different tamper-sensitive circuit regions on different tamper-sensitive layers can advantageously be electrically connected, for example, to the same comparator circuit or Wheatstone bridge circuit of the monitoring circuits. In this way, any number of connection configurations are possible.For example, if each of two tamper-sensitive backing layers has 30 tamper-sensitive circuit regions and each of two tamper-sensitive frames has 4 tamper-sensitive circuit regions, the resulting 68 tamper-sensitive circuit regions can be connected in any configuration within the secure space to create the desired arrangement of circuit networks within the secure space that is monitored for changes in electrical resistance or tampering. In this regard, it should be noted that the power supply or battery for the tamper-sensitive sensor may be located outside the secure space, with the sensor designed to trigger and destroy any protected or critical data if the power supply or battery is tampered with.

[0079] Fig. 11 is an enlarged fragmentary view of the tamper-responsive assembly of Fig. 8A through 9 show a tamper-evident electronic circuit structure 1100 having a plurality of tamper-evident sensors 821, 822 disposed on the inner surface 825 of the housing 820. As illustrated, in one embodiment, the housing 820 and the inner sidewall tamper-evident sensor 821 are aligned at the bottom edge and extend into a through-going groove or trench 812 in the multilayer printed circuit board 810 containing or associated with the electronic circuitry to be protected, as discussed above. The tamper-evident sensors 821, 822 may overlap, for example, by several millimeters or more to provide additional tamper protection along the edge where the tamper-evident sensors 821, 822 meet within the electronic assembly housing 820.

[0080] Fig. 12 illustrates an example of a process for adhering a tamper-responsive sensor 1200 to the inner surface 825 of the housing 820. In this example, a single tamper-responsive sensor 1200 replaces the tamper-responsive sensors 821, 822 in the example of Fig. 11. The attachment device and the approach of Fig. 12 could also be applied to attaching the plurality of tamper-evident sensors 821, 822, for example, to the inner surface of the electronic assembly package 820. As illustrated, a connecting fastener 1210 may be used in conjunction with a first push-and-clamp mechanism 1211 and a second push-and-clamp mechanism 1212 to hold the tamper-evident sensor 1200 in place while an adhesive 1205 cures between the tamper-evident sensor and the inner surface 825 of the package 820. It should be noted that, in one or more embodiments, the radius of the tamper-evident sensor 1200 may vary in the corners of the package to accommodate tolerances of the flexible tamper-evident sensor having the one or more molded, flexible layers.

[0081] Fig. 13A to 13C illustrate an example process for adhering the tamper-responsive electronic circuit structure 1100 of Fig. 11 to the inner surface 825 of the electronics housing 820. As shown in the isometric bottom view of Fig. 13A, the inner surface 825 of the electronics housing 820 includes an inner sidewall surface 1300 and an inner main surface 1301. The tamper-respondent sensor 821, also referred to herein as an inner sidewall tamper-respondent sensor, may be attached to the inner sidewall surface of the housing 820 using an adhesive, such as a thermosetting adhesive, along with a suitable interconnect fastener and push and clamp mechanisms (not shown), for example, to align the tamper-respondent sensor 821 with the lower edge of the inner sidewall surface 1300.

[0082] As in Fig. 13B, in one or more implementations, the tamper-responsive sensor 822 may be simultaneously or subsequently bonded to the inner major surface 1301 ( Fig. 13A) of the electronics housing 820. It should be noted that in this embodiment, the tamper-responsive sensor 822 is sized to at least partially overlap the tamper-responsive sensor 821 that is attached to the inner sidewall surface 1300 ( Fig. 13A). This overlap is shown in more detail in the partial enlargement of an inner corner 1302 of the electronics housing 820 in Fig. 13C. By providing two or more discrete tamper-responsive sensors, attaching the tamper-responsive electronic circuit structure to an electronics package is advantageously facilitated by allowing greater flexibility for aligning a particular sensor with a particular portion of the electronics package, such as the lower edge of the inner sidewall surface of the electronics package 820, as in the example of Fig. 13A to 13C is possible.

[0083] As in Fig. 13C, an inner corner 1302 of the electronics housing 820 may be shaped with one or more curved portions and one or more flat portions of the angled sidewall to facilitate wrapping the tamper-responsive sensor 821 over the inner sidewall surface 1300 (as further explained below). It should be noted that various tamper-responsive sensors may overlap within the electronics housing 820, and wrap-around arrangements may be employed, such as the external wrapping of sensors around the electronics housing shown in Fig. 6A to 6G. In the embodiment of Fig. 13A to 13C, the connections to the resistor networks of the tamper-responsive sensors 821, 822 may be provided in the region of overlap between the sensors, which in the embodiment of Fig. 8A to 10 facilitate defining the safe space between the electronics housing and the multilayer printed circuit board.

[0084] One consideration in a tamper-evident assembly, and more specifically, a tamper-evident electronic circuit structure, for example, as described herein, arises from the need to pass the interior sidewall-located tamper-evident sensor through one or more interior sidewall corners of an electronics enclosure, as described. As noted above, in one or more embodiments, the tamper-evident electronic circuit structure includes one or more tamper-evident sensors adhesively attached or secured to interior surfaces of the electronics enclosure. These interior surfaces include an interior main surface and an interior sidewall surface, for example, having at least one interior sidewall corner.As noted, the one or more tamper-sensitive sensors may each be formed from one or more flexible layers having circuit lines on one or more layers defining tamper-detection networks, such as resistor networks, that may be connected to monitoring circuitry for detecting intrusions into the secure space defined by the tamper-sensitive assembly. During manufacturing, the flexible layers of the one or more tamper-sensitive sensors may stretch and possibly warp within one or more interior sidewall corners of the electronics enclosure while the sensor is being attached to the enclosure.This stretching or warping within the corner(s) could result in the breakage of one or more circuit lines defining the tamper-detection networks to be monitored, thereby rendering the tamper-responsive assembly unusable for its intended use. Furthermore, any distortion of the one or more tamper-responsive sensors across the interior surface, such as at the interior sidewall corner(s) of an interior sidewall panel, could result in potential breakage points, which would cause the tamper-responsive assembly to fail a NIST FIPS 140-2 Level 4 security test. Therefore, the following describes, with reference to . Fig. 14A through 18 describe various improvements to tamper-responsive assemblies as disclosed herein that solve this problem.

[0085] Fig. 14A & 14B illustrate an embodiment of an electronics package 1400 similar to the package 820 described above in connection with Fig. 8A to 13C. With reference in its entirety to Fig. 14A & 14B, the electronics housing 1400 in this example includes an interior major surface 1401, which may be substantially flat, and an interior sidewall surface 1402, which in this example connects to the interior major surface 1401 via a curved (or rounded) transition region 1403 around the inner perimeter of the electronics housing 1400. The region 1403 provides a gradual transition between the interior sidewall surface 1402 and the interior major surface 1401, which in one or more embodiments may be oriented orthogonally to each other. In the illustrated configuration, the electronics housing 1400 also includes a plurality of interior sidewall corners 1410, which may be configured to facilitate a transition between adjacent sides of the electronics housing 1400. For example, in the enlarged view of Fig. 14B illustrates an inner sidewall corner 1410 connecting to a first side 1404 and a second side 1405 of the electronics enclosure 1400. In one or more implementations, each inner sidewall corner may be similarly configured. In the exemplary embodiment, shown merely by way of example, the inner sidewall corner 1410 includes a flat angled sidewall portion 1411 and first and second curved sidewall portions 1412, 1413 located on opposite sides of the flat angled sidewall portion 1411, as shown.

[0086] For example, a flat angled sidewall portion 1411 may be oriented at a 45° angle to the adjacent first side 1404 and second side 1405 of the electronics enclosure 1400, which may be perpendicular to each other in one or more embodiments. In one or more implementations, the first and second curved sidewall portions 1412, 1413 may have similar bend radii, for example, approximately five times or more than the thickness of the tamper-responsive sensor attached to the inner sidewall surface of the electronics enclosure 1400.In the illustrated example, the transition region 1403 extends between the inner sidewall surface 1402 and the inner main surface 1401 within the inner sidewall corners 1410, where a lower portion 1411' of the flat angled sidewall section 1411 curves outwardly in transition to the inner main surface 1401, and lower portions 1412', 1413' of the first and second curved sidewall sections 1412, 1413 also curve further outwardly in transition to the inner main surface 1401, as illustrated. It should be noted that the corner configuration of . Fig. 14A & 14B is shown merely as an example and that the present invention may be used with other corner constructions without departing from the concepts disclosed herein. Furthermore, as noted, in one or more implementations, the electronics housing 1400 may be used in conjunction with a multilayer printed circuit board, such as the one described above in connection with Fig. 8A to 12 to define a secure space around one or more electronic components or an electronic assembly comprising, for example, an encryption and / or decryption module and associated memory.

[0087] The electronics enclosure 1400 may be constructed from a variety of materials and have a variety of different configurations. In one or more implementations, the enclosure may be a rigid, thermally conductive enclosure (made, for example, from a metal material) to facilitate conduction of heat from one or more electronic components within the secure space defined (at least in part) by the tamper-responsive assembly. It should also be noted that the rectangular configuration of the electronics enclosure 1400 could be replaced by any of a variety of different enclosure configurations, each of which may include one or more interior sidewall corners configured, for example, as shown in Fig. 14A & 14B illustrated.

[0088] Fig. 15A & 15B illustrate bottom isometric views of another embodiment of a tamper-responsive assembly employing the electronics package 1400. Referring generally to Fig. 15A & 15B, a tamper-responsive assembly 1500 includes, in one or more implementations, the electronics housing 1400, which, as noted, is intended to at least partially enclose one or more electronic components or an electronic assembly to be protected. The electronics housing 1400 includes an interior main surface and an interior sidewall surface including at least one interior sidewall corner, such as described above in connection with Fig. 14A & 14B. Tamper-evident assembly 1500 further includes a tamper-evident electronic circuit structure including at least one tamper-evident sensor attached to and at least partially covering the one or more interior surfaces of electronics enclosure 1400. As further explained below, the one or more tamper-evident sensors are configured to facilitate good contact and adhesion of the sensor to the interior surfaces of the enclosure, such as the one or more interior sidewall corners of electronics enclosure 1400, such that secure coverage of the interior surface(s) of the electronics enclosure by the one or more tamper-evident sensors is provided.

[0089] As illustrated, in one or more implementations, the tamper-responsive electronic circuit structure associated with the electronics package 1400 may include an inner sidewall tamper-responsive sensor 1510 and an inner major surface tamper-responsive sensor 1520 along with a security band 1530.In the illustrated example, the inner sidewall tamper-responsive sensor 1510 may be formed with an integrated flex ribbon cable or extension 1511 to facilitate electrical connection of the at least one resistor network within the inner sidewall tamper-responsive sensor 1510 to corresponding monitoring circuits (not shown) located, for example, within the secure space defined at least in part by the tamper-responsive assembly of FIG. Fig. 15A & 15B. Similarly, the inner main surface tamper-responsive sensor 1520 may be configured with an integrated flex ribbon cable or extension 1521 to also facilitate electrical connection of the inner main surface tamper-responsive sensor 1520 to the monitoring circuitry. A bonding agent (not shown), such as a thermosetting adhesive, may be used to bond the inner sidewall tamper-responsive sensor 1520 to the inner sidewall surface 1402 ( Fig. 14A) and on inner side wall corners 1410 ( Fig. 14A). A similar adhesive could be used to adhere the inner major surface tamper-responsive sensor 1520 to the inner major surface 1401 ( Fig. 14A) and to adhere to the inner sidewall tamper-responsive sensor 1510 where the sensors overlap. The security band 1530 may further be adhesively secured over the overlap between the inner major surface tamper-responsive sensor 1520 and the inner sidewall tamper-responsive sensor 1510, such that, in one or more implementations, a transition region 1403 ( Fig. 14A) between the inner sidewall surface and the inner main surface around the inner perimeter of the electronics housing 1400.

[0090] It should be noted that the Fig. 15A & 15B, the inner sidewall tamper-responsive sensor 1510 and the inner main surface tamper-responsive sensor 1520 are discrete tamper-responsive sensors that at least partially overlap and facilitate defining a secure space around the at least one electronic component to be protected. For example, the secure space may be formed by inverting and securing the illustrated tamper-responsive assembly of Fig. 15A & 15B on a multilayer printed circuit board with an integrated tamper-responsive sensor, such as described above.

[0091] Fig. Figure 16A illustrates an embodiment of the inner sidewall tamper-responsive sensor 1510 of Fig. 15A & 15B. In this embodiment, the inner sidewall tamper-evident sensor 1510 includes at least one first layer 1600 having opposing first and second sides 1601, 1602 and circuit lines 1605 extending substantially across the entire flexible layer and forming at least one tamper-detection network as described herein. For example, the circuit lines 1605 may be disposed on the first side 1601 and / or the second side 1602 of the at least one flexible layer 1600. It should be noted that the at least one flexible layer 1600 may be fabricated as a conventional security sensor layer or may be fabricated as one of the enhanced tamper-evident sensors described herein.In particular, the at least one flexible layer 1600 of the inner sidewall tamper-responsive sensor 1510 could be a shaped, flexible layer such as one of the layers shown in FIG. Fig. 4A to 5H or multiple interwoven tamper-responsive sensors as shown in Fig. 7A to 7C, although illustrated as an unformed, flexible layer. As noted, the extension 1511 may extend from the inner sidewall tamper-responsive sensor 1510 such that electrical connection of the at least one resistor network of the inner sidewall tamper-responsive sensor 1510 to corresponding monitoring circuits (not shown) disposed, for example, within the secure space defined at least in part by the tamper-responsive assembly of Fig. 15A & 15B. As illustrated, in one or more implementations, the inner sidewall tamper-respondent sensor 1510 has a sufficient length to enclose the interior of the electronics housing, covering its inner sidewall surface, and overlapping it at its ends. Further, a plurality of slots 1610 are provided within the inner sidewall tamper-respondent sensor 1510.These multiple slots 1610 are sized and positioned along the inner sidewall tamper-respondent sensor to approximately align (in one or more embodiments) with respective inner sidewall corners of the electronics enclosure to facilitate good contact and adhesion and flexion of the sensor within the inner sidewall corners of the electronics enclosure, for example, by allowing areas of overlap of the inner sidewall tamper-respondent sensor over itself.

[0092] Fig. 16B & 16C illustrate one embodiment of the inner sidewall tamper-responsive sensor 1510 mounted within the electronics housing 1400. As illustrated, in the exemplary embodiment, the inner sidewall tamper-responsive sensor includes first and second slots that are respectively at least partially formed over the first and second curved sidewall portions 1412, 1413 ( Fig. 14B) of the associated inner sidewall corner 1410 to be covered. These first and second slots are spaced such that they are located on opposite sides of the flat angled sidewall portion 1411 ( Fig. 14B) of the inner sidewall corner 1410 and facilitate reducing the amount of material in the corner and thereby ensuring good contact and adhesion of the inner sidewall tamper-responsive sensor 1510 to the inner sidewall surface 1402 ( Fig. 14A) of the electronics housing, including at the inner sidewall corners 1410 thereof, while reducing stress on the sensor within the corner(s). For example, the plurality of slots 1610 allow the inner sidewall tamper-responsive sensor to overlap itself at the inner sidewall corners, as illustrated. Note that in this configuration, the inner sidewall tamper-responsive sensor 1510 has a width that allows the sensor to traverse the transition region 1403 ( Fig. 14A) and extends partially over the inner major surface 1401 of the electronics housing 1400. It should also be noted that one or more uncovered areas 1615 may result from the presence of the slots when the inner sidewall tamper-responsive sensor 1510 is wrapped around the inner sidewall surface as shown, with portions of the inner

[0093] Sidewall surface at the one or more inner sidewall corners, for example, along the seams where the inner sidewall tamper-responsive sensor overlaps at the corner. As explained below, these areas 1615 may be covered or protected by corner tabs of the inner main surface tamper-responsive sensor 1520 after this sensor and its corner tabs have been adhered to the assembly. This is exemplified in Fig. 17A to 17C.

[0094] With reference in its entirety to Fig. 17A through 17C, the inner major surface tamper-respondent sensor 1520 includes at least one flexible layer 1700 having opposing first and second sides 1701, 1702 and circuit lines 1705 extending substantially across the entire flexible layer 1700 and forming at least one tamper-detection network, for example, as described herein. For example, the circuit lines 1705 are disposed on the first side 1701 and / or the second side 1702 of the at least one flexible layer 1700, as described. As noted above, the at least one flexible layer 1700 may be fabricated as a conventional security sensor layer or fabricated as one of the enhanced tamper-respondent sensors described herein.In particular, the at least one flexible layer 1700 of the inner major surface tamper-responsive sensor 1520 could be a shaped, flexible layer such as one or more of the layers shown in FIG. Fig. 4A to 5H or multiple interwoven tamper-responsive sensors as shown in Fig. 7A to 7C, although illustrated as an unformed, flexible layer. As noted, the extension 1521 may be formed integrally with the inner major surface tamper-responsive sensor 1520 to facilitate electrical connection of the at least one associated resistor network to monitoring circuits (not shown) within the secure space defined at least in part by the tamper-responsive assembly of Fig. 15A & 15B; for example, in conjunction with a multilayer printed circuit board incorporating a tamper-responsive sensor as described above.

[0095] In the illustrated configuration, a plurality of corner tabs 1710 are provided, with at least one corner tab 1710 being provided at the at least one inner sidewall corner. In the illustrated exemplary embodiment, two corner tabs 1710 are provided at each corner of the inner major surface tamper-responsive sensor 1520. These corner tabs 1710 include circuit lines 1705 ( Fig. 17A) and are sized to each cover one of the uncovered areas 1615 in the inner sidewall tamper-responsive sensor and housing assembly that remain after the inner sidewall tamper-responsive sensor 1510 is attached to the electronics housing 1400, as shown in Fig. 16B & 16C. In particular, it should be understood by those skilled in the art that the corner tabs 1710 include respective portions of the at least one tamper-detection network provided by the tamper-responsive sensor 1520 located on the inner major surface, such that if an attempt were made to breach the tamper-responsive assembly 1500 through the underlying uncovered areas 1615 of the inner sidewall surface, contact would be made with the respective corner tab, resulting in detection of the attempted breach.

[0096] As above in connection with Fig. 15A & 15B, an increase in the overlap of the inner sidewall tamper-responsive sensor 1510 ( Fig. 15A) and the tamper-responsive sensor 1520 located on the inner main surface ( Fig. 15) may be provided in one or more implementations by one or more physical security structures such as the security band 1530. A potential vulnerability of a tamper-responsive assembly as described herein would be the overlap between two or more tamper-responsive sensors, such as an overlap between an inner sidewall tamper-responsive sensor and an inner main surface tamper-responsive sensor.For example, an attack on a tamper-sensitive assembly could involve drilling through the package and chemically attaching an overlapping bonding surface between two tamper-sensitive sensors of the tamper-sensitive electronic circuit structure, such as the overlapping surface where the inner main surface tamper-sensitive sensor 1520 is adhesively secured over the inner sidewall tamper-sensitive sensor 1510. To overcome this problem, a physical security structure, such as a security tape 1530, may be provided.It should be noted that the security band 1530 is merely one embodiment of a physical security structure that could be deployed to at least partially overlie and physically secure in place one or more tamper-responsive sensors covering one or more interior surfaces of an electronics enclosure, as described herein.

[0097] Generally speaking, in one or more implementations, a tamper-evident assembly is disclosed herein that includes an electronics housing to at least partially enclose at least one electronic component to be protected, the electronics housing including an interior surface. The tamper-evident assembly further includes a tamper-evident electronic circuit structure including a tamper-evident sensor at least partially lining and covering the interior surface of the electronics housing. The tamper-evident sensor may include a flexible layer having opposing first and second sides and circuit lines substantially covering at least one of the first side and the second side of the flexible layer, thereby forming at least one tamper-evident network as described herein.The flexible layer of the tamper-responsive sensor could be an unshaped sensor layer or a shaped sensor layer according to one or more of the embodiments of sensor layers described herein.

[0098] The tamper-responsive assembly further includes a physical security structure, such as at least one security element, that is at least partially overlying and physically securing the tamper-responsive sensor that at least partially covers the inner surface of the electronics housing. In the embodiment of Fig. 15A & 15B, the security band 1530 is illustrated, which includes a plurality of security elements 1531, as in the enlarged view in Fig. 18. It should be noted that the security structure, such as the security band 1530, could comprise a single element or multiple elements depending on the desired design. In the example of Fig. 15A, Fig. 15B & 18, two substantially identical U-shaped security elements 1531 are illustrated by way of example only. In the illustrated embodiment, the security elements 1531 are spaced apart with gaps 1532 between them. By providing two or more security elements 1531 to define a desired physical security structure (such as the security band 1530), manufacturing tolerances within the tamper-evident assembly can be better accommodated. For example, the gaps 1532 between adjacent security elements of the plurality of individual security elements 1531 may be on the order of several millimeters.It should be noted that, although illustrated as two security elements 1531, any number of physical security elements could be provided within the tamper-respondent assembly as desired, and any number of security structures, such as multiple security bands or plates, could be provided within the tamper-respondent assembly to provide additional mechanical fixing of the one or more tamper-respondent sensors in place over the interior surface of the electronics housing.

[0099] In the example of Fig. 15A, Fig. 15B & 18, the physical security structure is configured as a security band or cuff having a plurality of individual security elements 1531 that extends substantially completely around the inner perimeter of the electronics housing 1400. The security band 1530 is sized and positioned to at least overlie the overlap of the inner main surface tamper-responsive sensor and the inner sidewall tamper-responsive sensor and physically fix them in place, as shown in Fig. 15A. In one or more implementations, the security band 1530 may be adhesively attached to the tamper-responsive sensors. Note that in this example, the security band 1530, which includes the security elements 1531, extends around the inner perimeter and including through the inner sidewall corners, as shown in Fig. 15A. In this manner, the security elements 1531 advantageously overlie and secure in place the one or more overlaps of the inner sidewall tamper-responsive sensor and the inner main surface tamper-responsive sensor at the inner sidewall corners of the electronics enclosure. For example, in the illustrated embodiment, the security band 1530, or more specifically, the security elements 1531, overlie the plurality of corner tabs 1710 ( Fig. 17C) projecting from the inner major surface tamper-evident sensor 1520 at the inner sidewall corners of the electronics enclosure, and physically secure them in place. This advantageously prevents attack on the tamper-evident assembly through the surfaces lined by the plurality of corner tabs projecting from the inner major surface of the tamper-evident sensor. The security band 1530 creates a mechanical barrier that prevents the tamper-evident sensors from being separated.

[0100] In one or more improved embodiments, the one or more security elements defining the security band, or more generally, the physical security structure, are formed (e.g., by stamping) from a metal material or metal alloy such as copper, soft stainless steel, etc. Furthermore, the one or more metal security elements may advantageously be electrically connected to ground to further enhance the detection capability of the tamper-responsive assembly.By forming the one or more security elements from a metal that is difficult to penetrate, an attempt to penetrate the security element would generate metal fragments that could potentially be drawn into the sensor layer(s) lining the interior surface of the electronics package, resulting in a greater likelihood of shorting or other damage to the circuit lines forming the one or more tamper-responsive networks of the sensor during the attack, and thus improving the detection capability of the tamper-responsive sensor.Furthermore, electrically grounding the one or more security elements would make it more likely that a short circuit would occur on one or more of the circuit lines forming the at least one tamper-detection network in the one or more associated tamper-responsive sensors if a drill were to come into contact with the one or more grounded security elements after drilling through one or more tamper-responsive sensors. Grounding the one or more security elements provides another path for current flow, advantageously increasing the likelihood that an attempt to tamper with the tamper-responsive assembly will be detected.It should be noted that grounding of the one or more security elements could be accomplished by any means, such as by electrically connecting the elements to one or more ground lines on the electronic assembly being protected by the tamper-responsive assembly, or (in certain of the embodiments disclosed herein) by electrically connecting the elements to one or more ground planes within the multilayer printed circuit board that partially forms the secure space around the electronic assembly being protected. In one or more implementations, the security element(s), or more generally, the security band or physical security structure, may be pre-wired (e.g.,by stamping) into the desired shape, for example, so that it receives and overlies the overlap between the tamper-responsive sensor located on the inner side wall and the tamper-responsive sensor located on the inner main surface, as in . Fig. 15A.

[0101] As a further improvement, increased sensor sensitivity to a tamper-evident event may be provided by fabricating the tamper-evident assembly, and in particular the tamper-evident sensor, to account for one or more regions of increased fragility or susceptibility to damage from mechanical stress resulting from or associated with a tamper-evident event. By locating circuit lines or traces of the tamper-evident sensor at least partially within the one or more regions of increased susceptibility to damage, there is an increased likelihood that one or more of the circuit lines may be damaged during the tamper-evident event due to the associated mechanical stress, thereby improving the ability to detect the tamper-evident event.The one or more vulnerability regions of the tamper-responsive sensor may be formed using a variety of approaches, including selectively laser ablating or etching the sensor, designing the sensor with cutout regions to define inner edges where stresses are concentrated, and / or directly adhering exposed circuit lines to a rigid surface of the tamper-responsive assembly. Fig. 19A to 20B exemplify examples of tamper-responsive assemblies having one or more tamper-responsive sensors that have one or more areas of increased susceptibility to damage due to mechanical stress associated with a tamper event.

[0102] With reference to Fig. 19A illustrates a tamper-responsive assembly 1900 including a structure 1901 with a rigid surface 1902. The structure 1901 could, by way of example only, comprise an electronics housing or enclosure that at least partially surrounds one or more electronic components to be protected. As a specific example, the rigid surface 1902 could be an outer surface of an electronics housing or an inner surface of an electronics housing. Fig. 6A to 6G illustrate exemplary embodiments of one or more tamper-responsive sensors of a tamper-responsive electronic circuit structure adhered to an outer surface of an electronics package, whereas Fig. 8A through 17C illustrate exemplary embodiments of one or more tamper-responsive sensors adhered to an interior surface of an electronics enclosure. Still further, structure 1901 could be or include any rigid structure of an electronic assembly or a cooling device associated with an electronic assembly to be protected. In one or more specific cases, structure 1901 could include a heat sink, such as a heat spreader.

[0103] As illustrated, the tamper-responsive assembly 1900 includes a tamper-responsive electronic circuit structure having a tamper-responsive sensor 1910. In the illustrated embodiment, the tamper-responsive sensor 1910 includes one or more flexible layers 1911 having opposing first and second sides 1912, 1913, and circuit lines 1915, 1915' that at least partially form at least one tamper-detection network. For example, the circuit lines may at least partially form at least one resistor network electrically connected to monitoring circuitry, such as described herein. For example, first circuit lines 1915 are disposed on the first side 1912, and second circuit lines 1915' are disposed on the second side 1913 of the flexible layer 1911.The circuit lines may have the same or different patterns as described above. It should also be noted that any number of flexible layers 1911 and any number of layers of circuit lines 1915, 1915' may be provided within the tamper-responsive sensor 1910, as described above, for example, in connection with FIG. Fig. 3A to 3E, the illustrated embodiment being provided by way of example only.

[0104] According to one or more aspects of the present invention, the circuit lines 1915 on the first side 1912 of the flexible layer 1911 are exposed, i.e., any overlying protective layer, such as a polyimide layer, is at least partially or completely removed in the area to be attached to the rigid surface 1902 of the structure 1901. It should be noted that the circuit lines 1915, 1915' may be formed from a variety of materials, including, for example, a metal or a metal alloy. For example, the first circuit lines 1915 could be formed from copper, silver, silver-carbon, nickel-phosphorus. Alternatively, other materials such as conductive ink or omega-ply ® or Ticer™ can be used.

[0105] In the exemplary embodiment, an adhesive 1920, such as a thermosetting material, is used to adhere or layer the tamper-responsive sensor 1910 to the rigid surface 1902. More specifically, in the illustrated embodiment, the exposed first circuit lines 1915 on the first side 1912 are directly adhesively attached to the rigid surface 1902 of the structure 1901. In one or more implementations, the adhesive 1920 is selected with a bond strength for attaching the first circuit lines 1915 to the rigid surface 1902 that is equal to or greater than a bond strength of the first circuit lines 1915 to the first side 1912 of one or more flexible layers 1911.In this way, if a tamper-evident event occurs that includes an attempt to physically separate the tamper-responsive sensor 1910 from the structure 1901, one or more of the first circuit lines 1915 are likely to separate from the flexible layer 1911 and thus be broken, with the resulting broken lines improving the ability of the tamper-responsive electronic circuit structure to detect the tamper-evident event.

[0106] In one or more embodiments, balancing elements could be provided between the rigid surface 1902 of the structure 1901 and the first side 1912 of the tamper-respondent sensor 1910 to ensure the presence of a gap between the first side 1912 of the tamper-respondent sensor 1910 and the rigid surface 1920, and thus ensure that the adhesive 1920 remains between the two surfaces during a manufacturing approach in which pressure can be applied to press the surfaces together, for example, to facilitate layering the tamper-respondent sensor 1910 onto the structure 1901. In one or more implementations, the balancing elements could be distributed throughout the adhesive 1920 and could, for example, comprise spherical elements 1922, such as glass beads, disposed within the adhesive.Alternatively, in one or more implementations, the rigid surface 1902 could be formed with one or more spacer elements extending from the surface at a desired gap distance.

[0107] Fig. Figure 19B illustrates an alternative embodiment of a tamper-responsive assembly 1900'. In this embodiment, the structure 1901 of Fig. 19A by an electronics housing 1400 as described above in connection with Fig. 14A & 14B, as another example. The electronics housing 1400 includes a rigid surface 1902', which may be, for example, the inner major surface 1401 ( Fig. 14A) or the inner side wall surface 1402 ( Fig. 14A) in the exemplary embodiment of Fig. 14A & 14B can act.

[0108] As in Fig. 19B, in one or more implementations, the tamper-responsive assembly 1900' may further include a tamper-responsive sensor 1910' and another structure 1930 having another rigid surface 1932. For example, in one or more implementations, another structure 1930 may include a cooling structure, such as a heat spreader, provided to facilitate cooling of one or more devices within the electronics package.

[0109] In one or more embodiments, the tamper-responsive sensor 1910' may comprise a stack of tamper-responsive layers bonded together via an adhesive layer 1925, such as a double-sided adhesive film similar to that described above in connection with Fig. 3C. However, in this example, the widths of the circuit lines and the spacing between lines may have any desired dimension, for example, the line widths and spacings described above of ≤ 200 µm, respectively. The tamper-responsive sensor 1910' includes multiple layers of circuit lines 1915, 1915' that may be electrically connected to define one or more tamper-detection networks, such as one or more resistive networks. Any of the various materials described herein or other known materials may be used to form the circuit lines.The circuit lines are provided on one or both sides of the respective flexible layers 1911, with the first circuit lines 1915, by way of example only, being provided on a first side of each flexible layer 1911 and the second circuit lines 1915' being provided on a second side of the layer. The flexible layers 1911 may be formed from any flexible dielectric material, such as a polyester material. Alternatively, the flexible layers 1911 could be formed from a crystalline polymer, such as the PVDF or Kapton described above, or another crystalline polymer material.

[0110] According to one or more aspects of the present invention, a portion of the circuit lines 1915 is exposed on the top side of the tamper-responsive sensor 1910', and a portion of the circuit lines 1915' is exposed on the bottom side. The exposed circuit lines 1915, 1915' are each layered onto the rigid surface 1902' of the electronics package 1400 or onto a rigid surface 1932 of another structure 1930 using an adhesive layer 1920, 1920', as illustrated. This portion of the tamper-responsive sensor 1910' that has been adhered to the electronics package 1400 and / or another structure 1930 defines the one or more regions of the tamper-responsive sensor that exhibit the increased susceptibility to damage from mechanical stress associated with a tamper event.That is, should a tamper-evident event attempt to detach the tamper-responsive sensor from the electronics package 1400 and / or the further structure 1930, the adhesive layers 1920, 1920' connecting the structures to the first side and the second side of the tamper-responsive sensor 1910' are likely to cause one or more of the exposed circuit lines 1915, 1915' to detach from the tamper-responsive sensor as the structures are separated, causing breaks in the circuit lines and thereby facilitating detection of the tamper-evident event by monitoring circuitry of the tamper-responsive electronic circuit structure.As noted, this result can be achieved by selecting the adhesive 1920, 1920' to have, for example, a bond strength equal to or greater than the bond strength that holds the circuit leads 1915, 1915' to their respective sides of the tamper-responsive sensor 1910'.

[0111] As noted, the circuit lines in the Fig. 19A & 19B may include a metal, such as copper, layered directly onto a rigid surface of the tamper-responsive assembly to define regions of the tamper-responsive sensor having increased vulnerability to damage from mechanical stress associated with a tamper-evident event, such as a tamper-evident event that physically disrupts the layering of the tamper-responsive sensor onto the rigid surface. In one or more other implementations, the one or more regions of the tamper-evident sensor having increased vulnerability may be provided by increasing the fragility of the tamper-evident sensor. This may be achieved, for example, by providing cutout regions in the sensor, such as channels, notches, openings, etc.that define one or more inner edges (or stress enhancers) where stresses are concentrated within the tamper-responsive sensor. In . Fig. Figures 20A & 20B show various examples of this approach.

[0112] With reference to Fig. 20A, one embodiment of a tamper-responsive assembly 2000 is illustrated. As shown, the tamper-responsive assembly 200 includes a tamper-responsive sensor 2001, with a plurality of peripheral edges 2002 of the tamper-responsive sensor 2001 being illustrated. As described herein, for example, with reference to Fig. As described in Figures 3A through 3E, the tamper-respondent sensor 2001 includes one or more flexible layers 2011 and one or more layers of circuit lines 2015 on one or both opposite sides of each flexible layer 2011. The circuit lines 2015 may be electrically connected to define one or more tamper-detection networks, such as one or more resistive networks. The tamper-respondent layers within the stack may be adhered to one another, for example, using a double-sided adhesive film 2025, as discussed above.

[0113] In this example, a plurality of regions 2032, 2042 within the tamper-responsive sensor 2001 with increased susceptibility to damage from mechanical stress are defined by providing the tamper-responsive sensor with one or more cutout regions 2030, 2040. In the exemplary embodiment, the cutout regions 2030 are illustrated as rectangular-shaped cutouts extending into the sensor from one or more peripheral edges 2002, and the cutout regions 2040 are triangular-shaped cutouts extending into the sensor from one or more peripheral edges 2002 of the tamper-responsive sensor 2001. In both cases, the cutout regions 2030, 2040 define inner edges 2031, 2041 where stresses are concentrated that extend (in this example) vertically through the tamper-responsive sensor 2001.These edges 2031, 2041 are stress enhancers that define the regions 2032, 2042, respectively, of increased susceptibility to damage within the tamper-responsive sensor 2001. The regions 2032, 2042 are locations within the sensor 2001 where stresses are concentrated due to the provision of the inner stress-concentrated edges 2031, 2041. For example, the circuit lines 2015 can be provided that follow the contours of the tamper-responsive sensor 2001 and extend at least partially through the respective regions 2032, 2042 of increased susceptibility to damage.In this way, if a tamper-evident event occurs, mechanical stress within the tamper-evident sensor is concentrated by the inner stress-concentrated edges 2031, 2041 in the regions 2032, 2042 of the sensor, thereby increasing the likelihood of a break in one or more of the circuit lines 2015 within these regions. This increased likelihood of a break facilitates detection of the tamper-evident event by the monitoring circuits of the tamper-evident electronic circuit structure.

[0114] It should be noted that the circuit lines 2015 may be provided in any desired configuration or pattern on the various flexible layers 2011 as described herein. For example, a rectangular grid of circuit lines could be provided in one or more layers that at least partially intersects the regions 2032, 2042 with increased susceptibility to damage from mechanical stress associated with a tampering event. It should also be noted that the regions 2032, 2042 of the tamper-responsive sensor are discrete regions of the sensor that are separate from the rest of the tamper-responsive sensor, which can be characterized as a region of normal robustness outside the regions 2032, 2042 created with the increased susceptibility to damage from mechanical stress.Therefore, the tamper-responsive sensor can be considered as divided into different regions, a region of normal robustness and regions 2032, 2042 of increased susceptibility to damage resulting from the provision of stress increasers within the tamper-responsive sensor.

[0115] It should be noted that, for example, depending on the tamper-evident event, any stress in one or more of the regions 2032, 2042 of increased susceptibility to damage may extend vertically across multiple layers of the tamper-responsive sensor 2001 or may be associated with one or more particular tamper-responsive layers (or flexible layers) within the tamper-responsive sensor 2001. In one or more implementations, the recesses, such as the recess regions 2030 and / or the recess regions 2040, may extend around a portion or the entire circumference of the tamper-responsive sensor 2001 in any desired configuration and number.Furthermore, any recess design that provides stress concentration areas within the tamper-responsive sensor, for example, due to the presence of one or more internal edges (or stress enhancers) where stress is concentrated, may be used. Additional embodiments of this concept are described in [ ]. Fig. 20B.

[0116] With reference to Fig. 20B, a tamper-responsive assembly 2000' is illustrated as including a tamper-responsive sensor 2001' of a tamper-responsive electronic circuit structure. The tamper-responsive sensor 2001' is partially illustrated, showing a corner thereof defined by peripheral edges 2002. In this implementation, a recessed region 2030 is again illustrated defining (for example) a plurality of inner stress-concentration edges 2031 that define one or more adjacent regions 2032 of the tamper-responsive sensor that have increased susceptibility to damage from mechanical stress within the sensor. As another example, one or more openings 2050 are formed in line with the recessed region 2030 and extend through the tamper-responsive sensor 2001'.The one or more openings 2050 include one or more inner edges 2051 where stresses are concentrated extending vertically through the tamper-responsive sensor 2001', each defining one or more regions 2052 within the tamper-responsive sensor that have increased susceptibility to damage from mechanical stress within the sensor encountered during a tampering event. The inner edges 2051 where stresses associated with the opening 2050 are concentrated, in turn, increase the likelihood of damage to those portions of the circuit lines 2015 of the tamper-responsive sensor 2001' that extend through the one or more regions of increased susceptibility to damage.For example, the likelihood of the tamper-responsive sensor 2001' detaching in areas 2052 with increased susceptibility to damage in response to a tamper event may be increased. Note that any mechanical stress within the tamper-responsive sensor may propagate through the sensor and be concentrated by the stress-concentrated inner edges 2051 within the areas 2052, resulting in increased susceptibility to damage of any circuit lines extending through these areas.

[0117] In the exemplary embodiment of Fig. 20B, the tamper-responsive sensor 2001' is illustrated as including one or more flexible layers 2011 having opposing first and second sides with circuit lines 2015 disposed on the opposing first and second sides. Protection layers 2026 are disposed over the first and second sides of the one or more flexible layers 2011 and the circuit lines 2015. The protection layers 2026 may comprise, for example only, a polyimide material.

[0118] As illustrated, cutout regions 2060 may additionally or alternatively be provided as one or more channels extending through the protective layers 2026 above and / or below the one or more flexible layers 2011 and the circuit lines 2015. These cutout regions 2060, in turn, have inner edges 2061 where stresses are concentrated, defining regions 2062 adjacent to the edges within the tamper-responsive sensor 2001' that have increased susceptibility to damage from machine stress occurring during a tamper-responsive sensor 2001'. As with the embodiments described above, the circuit lines 2015 may extend at least partially through regions 2062 with increased susceptibility to damage, and therefore, if a tamper-responsive sensor 2001' occurs,that creates a mechanical stress within the tamper-responsive sensor 2001', any circuit lines within the regions of increased susceptibility to damage, for example, in regions adjacent to the inner edges 2061 where stresses are concentrated, become damaged or break (that is, compared to the rest of the tamper-responsive sensor, which has been characterized above as the region of the sensor with normal robustness), thereby increasing the probability of detection of the tamper-evident event by the monitoring circuits of the tamper-responsive electronic circuit structure comprising the tamper-responsive sensor 2001'.

[0119] Those skilled in the art will recognize that various improvements in creating a secure space for housing one or more electronic components, such as one or more encryption and / or decryption modules and associated components of a data transmission card or other electronic assembly, are disclosed herein. In certain embodiments, the tamper-responsive assembly or tamper-resistant electronic package includes a tamper-responsive electronic circuit structure having one or more tamper-responsive sensors of various configurations, for example, disposed outside or inside an electronic housing intended to contain the electronic component(s) or electronic assembly to be protected.The tamper-responsive electronic circuit structure may further include tamper-detection monitoring circuitry that monitors, for example, for changes in electrical resistance in one or more tamper-detection networks, such as one or more resistor networks defined (at least in part) by circuit lines within the one or more tamper-responsive sensors.

[0120] In one or more embodiments, the tamper-responsive sensor may be implemented as a narrow-pitch flex circuit formed, for example, from multiple stacked layers of a flexible film such as the crystalline polymer material described above, with Kapton being a specific example. Circuit lines are provided and electrically connected on one or more sides of each flexible layer to facilitate defining one or more tamper-detection networks of the tamper-responsive sensor. In one or more implementations, the line width and pitch may be significantly reduced in size compared to conventional approaches, for example, to ≤ 200 µm.These circuit lines may be formed from any suitable material, including a metal or metal alloy such as copper, silver, nickel-phosphorus (NiP), omega-ply. ® or Ticer™. The flexible layers containing the circuit lines are encased in polyimide, for example, so that the circuit lines within the tamper-sensitive sensor are not exposed, and the tamper-sensitive sensor provides reliable protection against mechanical or physical intrusion by the sensor into a secure space defined at least in part by the tamper-sensitive sensor.

[0121] A variety of tamper-evident assembly configurations are disclosed herein, wherein an adhesive may be employed in one or more external bonding areas on a surface of one or more tamper-evident sensors, for example, to secure a tamper-evident sensor in a working position within the tamper-evident assembly. For example, the adhesive may be employed to maintain a particular tamper-evident sensor configuration around an electronics package, to interconnect two or more tamper-evident sensors in a multiple-sensor configuration, or to position a tamper-evident sensor relative to an electronics package of a tamper-evident assembly, such as over an internal surface of an electronics package.These outer bonding areas could be vulnerable to chemical attack on the adhesive.

[0122] Therefore, as a further improvement, increased sensitivity to a tamper-evident event, and in particular to a tamper-evident event at an external connection or overlap region of the sensor, may be provided by fabricating the tamper-evident assembly to include conductive traces positioned and fabricated to exhibit increased mechanical and / or chemical fragility or susceptibility to damage from a tamper-evident event. For example, one or more conductive traces within one or more connection regions of one or more tamper-evident sensors may be exposed, and an adhesive may be provided that makes contact with the one or more conductive traces within the one or more connection regions of the one or more tamper-evident sensors.By establishing direct contact of the adhesive with the conductive traces, any attempt at mechanical and / or chemical attack on the adhesive to facilitate gaining access to the secure space within the tamper-evident assembly is more likely to damage one or more conductive traces and thus be detected. In this regard, it should be noted that by forming the conductive traces from a chemically damageable or dissolvable conductive material, the conductive traces are likely to be damaged during a chemical attack on the adhesive. Thus, the exposed conductive traces provide increased fragility or vulnerability to mechanical and / or chemical attack on the one or more external interconnect regions.

[0123] As noted, the at least one outer connection region may be a region of the one or more tamper-responsive sensors in which the sensor adheres to another surface, such as the surface of a rigid structure of the tamper-responsive assembly or the surface of another tamper-responsive sensor, in an embodiment with multiple tamper-responsive sensors, or even to another region of the same tamper-responsive assembly, as (for example) in Fig. 6A. In each of these examples, one or more conductive traces could be provided to form, for example, an external tamper-detection network that is at least partially exposed on a surface of the one or more tamper-responsive sensors within the one or more connection regions of the sensor(s).

[0124] In one or more embodiments, the one or more conductive traces may be individual conductors from the unexposed circuit lines on the flexible layers within the one or more tamper-responsive sensors.For example, and as noted, conductive traces may be formed of a chemically damageable or dissolvable material that is susceptible to damage during a chemical attack on the adhesive within the one or more connection regions of the one or more tamper-responsive sensors to facilitate detection of the chemical attack, whereas the unexposed circuit lines forming the tamper-responsive sensor may be formed of a different conductive material (and may even have a different line width and / or spacing between lines), for example, to facilitate ensuring that the one or more electronic components are protected by the sensor against a mechanical tamper event.In one or more examples, the circuit lines within the one or more tamper-responsive sensors may be smaller and have a narrower pitch than the conductive traces exposed on the surface of the one or more tamper-responsive sensors within the one or more connection regions.The one or more conductive traces forming the external tamper-detection network may, depending on the implementation, be placed on the one or more tamper-sensitive sensors at any location susceptible to chemical attack, for example, where adhesive is used to connect the tamper-sensitive sensor to another surface of the tamper-sensitive assembly, such as an electronics housing or to another tamper-sensitive sensor of the assembly, or even to itself.

[0125] Fig. 21A through 21C illustrate an embodiment of a tamper-evident assembly having one or more tamper-evident sensors with conductive traces positioned and fabricated to facilitate detection of mechanical and / or chemical attack on an adhesive of the tamper-evident assembly.

[0126] With reference to Fig. 21A, a tamper-responsive assembly 2100 is illustrated having a structure 2101 with a rigid surface 2102. The structure 2101 is illustrated, for example, as an electronics housing or enclosure that at least partially surrounds one or more electronic components 802 to be protected. As a specific example, the rigid surface 2102 is illustrated (for example) as an inner surface of the electronics housing, such as an inner surface of the electronics housing 1400 described above in connection with Fig. 14A to 15B. The embodiment of Fig. 21A is used, by way of example only, in connection with the implementation of Fig. 8A to 17C, wherein one or more tamper-responsive sensors are adhered to an interior surface of an electronics package. In this example, conductive traces 2120 may be provided between discrete first and second tamper-responsive sensors (such as interior sidewall tamper-responsive sensor 1510' and interior main surface tamper-responsive sensor 1520'), or alternatively or additionally, conductive traces 2120' may be provided between one or more of the tamper-responsive sensors and the interior surface of the package.

[0127] It should also be noted that in one or more other implementations, the conductive traces described herein as being susceptible to damage during chemical attack on the adhesive could be disposed between one or more tamper-responsive sensors and an outer surface of a structure, such as an outer surface of an electronics package. In this regard, reference is made to the embodiments of Fig. 6A through 6G, in which one or more tamper-responsive sensors of a tamper-responsive electronic circuit structure may be adhered to an external surface of an electronic package. Still further, the conductive traces forming the external tamper-detection network may be located between the tamper-responsive sensor and any rigid structure of an electronic assembly or a cooling device of an electronic assembly to be protected. For example, the conductive traces disclosed herein could be disposed between one or more tamper-responsive sensors and a heat sink, such as a heat spreader.

[0128] As illustrated, in one or more implementations, the tamper-responsive electronic circuit structure of the tamper-responsive assembly 2100 may include an inner sidewall tamper-responsive sensor 1510' and an inner major surface tamper-responsive sensor 1520', each having one or more tamper-detection networks, such as one or more unexposed tamper-detection networks formed by circuit lines on one or more flexible layers, such as described above. The one or more tamper-detection networks are electrically connected to suitable monitoring circuitry (not shown), for example, located within the secure space 801 defined by the tamper-responsive assembly 2100.It should be noted that in this example, the inner sidewall tamper-responsive sensor 1510' and the inner main surface tamper-responsive sensor 1520' are discrete first and second tamper-responsive sensors that at least partially overlap and facilitate defining the secure space around the at least one electronic component 802 to be protected. For example, the secure space may be defined by attaching the electronics package to a multilayer printed circuit board 810 having an integrated tamper-responsive sensor 811, such as described above in connection with FIG. Fig. 8A through 10. It should further be noted that in the illustrated configuration, the inner sidewall tamper-evident sensor 1510' may be bonded to an inner sidewall surface of the electronics enclosure via an adhesive 2110, partially wrapping around and over the inner major surface of the electronics enclosure, as shown. This allows the overlap region 2105 of the inner sidewall tamper-evident sensor 1510' and the inner major surface tamper-evident sensor 1520' to occur at the flat portion of the inner major surface of the structure 2101.An adhesive 2115 is provided to bond the inner main surface tamper-responsive sensor 1520' to the inner main surface of the structure 2101, as well as to the inner sidewall tamper-responsive sensor 1510' in one or more overlap regions 1205. The adhesives 2110, 2115 may be the same or different adhesives. In one or more implementations, the adhesives 2110, 2115 may be a thermosetting material, such as a thermally conductive epoxy.

[0129] As noted, one or more conductive traces 2120 may be provided at least partially exposed on one or more of the tamper-responsive sensors 1510', 1520' of the tamper-responsive assembly 2100 to provide enhanced tamper-detection protection. For example, one or more conductive traces 2120 are illustrated in the overlap region 2105 between the inner sidewall tamper-responsive sensor 1510' and the inner major surface tamper-responsive sensor 1520' as an example.Additionally or alternatively, one or more conductive traces 2120' could be provided as part of the same or different tamper detection network(s) on a surface of the inner sidewall tamper-responsive sensor 1510' between the inner sidewall tamper-responsive sensor 1510' and an inner sidewall of the structure 2101 and / or on a surface of the inner major surface tamper-responsive sensor 1520' between the inner major surface tamper-responsive sensor 1520' and the rigid surface 2102 of the structure 2101.In one or more implementations, the conductive traces 2120, 2120' in the one or more interconnect regions are formed from a chemically damageable or dissolvable conductive material that is susceptible to wetting or other damage during chemical attack on the adhesive 2110, 2115 upon direct contact therewith. The damage may cause one or more portions of the conductive traces, and thus one or more portions of the one or more associated tamper-detection networks defined (at least in part) by the traces and monitored by the tamper-responsive electronic circuit structure, to disintegrate, thereby facilitating detection of the tamper event.It should be noted that the chemically soluble conductor used to form the conductive traces may be the same or a different material than the material used to form the unexposed circuit lines that define the one or more tamper-detection networks of the respective tamper-responsive sensor.

[0130] Generally speaking, the conductive traces may be formed from a chemically damageable, conductive material and provided in any connection area external to one or more sensors, where, for example, an adhesive bonds the respective tamper-responsive sensor to another surface, such as another surface of the tamper-responsive assembly. For example, the chemically dissolvable material used to form the conductive traces may comprise at least one of carbon, silver, or carbon-silver. For example, the one or more conductive traces of the respective one or more tamper-detection networks may be formed from a carbon-loaded conductive material, a silver-loaded conductive material, or a carbon and silver-loaded conductive material.It should also be noted that different conductive traces may be in the same or different tamper detection networks, and that the conductive traces may be in the same or a different tamper detection network than the network(s) defined by the unexposed circuit lines of the sensor.

[0131] Fig. Figure 21B illustrates a modified version of the inner major surface tamper-responsive sensor 1520' described above in connection with Fig.17A. As described above, the inner major surface tamper-responsive sensor 1520' includes one or more flexible layers having opposing first and second sides, and circuit lines on the one or more flexible layers that at least partially form at least one tamper-detection network, such as at least one resistive network, where the circuit lines may be disposed on the first side and / or the second side of the one or more flexible layers.For example, multiple flexible layers could be provided within a stack, with circuit lines defined on each side of each flexible layer within the stack in any desired pattern and network design to facilitate detection of a mechanical attempt to gain access to the secure space by the tamper-responsive sensor.

[0132] In the example of Fig. 21B, a plurality of conductive traces 2120 are provided around the perimeter of the inner main surface tamper-responsive sensor 1520' in a region aligned with a connection region of the tamper-responsive sensor, and in particular aligned with an overlap region of, for example, the inner sidewall tamper-responsive sensor 1510', such as in Fig. 21A. In this context, it should be noted that two conductive traces 2120 are shown merely as an example. One or more than two conductive traces in any desired pattern could be provided within the one or more connection regions. It should also be noted that in the example of Fig. 21A, the connection area comprises substantially the entire upper surface of the inner main surface tamper-responsive sensor 1520', since the inner main surface tamper-responsive sensor 1520' is bonded to either the rigid inner main surface 2102 ( Fig. 21A) or the tamper-responsive sensor 1510' located on the inner side wall ( Fig. 21A). The conductive paths 2120 are Fig. 21B in the overlap area 2105 ( Fig. 21A) between the two manipulation-responsive sensors of the Fig. 21A. It should be noted that in this implementation, a tamper-detection network is formed at least in part by the conductive traces 2120, and that this network may further include the unexposed circuit lines 2121, such as unexposed circuit lines within the tamper-responsive sensor 1520' itself. That is, a tamper-detection network may include both exposed conductive traces 2120 and unexposed circuit lines 2121, as desired for a particular application. The unexposed circuit lines may be provided within the tamper-responsive sensor, for example, to complete the tamper-detection network where it is not required externally for tamper-detection purposes. In the implementation of Fig. 21B, the unexposed circuit lines 2121 are shown extending within the integrated flex ribbon cable or extension 1521' of the inner main surface tamper-responsive sensor 1520'. The integrated flex ribbon cable or extension 1521' would be used in the implementation of Fig. 21A, for example, may be located within the secure space 801, such as to facilitate electrical connection of the inner major surface tamper-responsive sensor 1520' to monitoring circuitry within the secure space. It should be further noted that in one or more other implementations where the tamper-responsive sensor connection region comprises only a portion of the outer surface of the tamper-responsive sensor, both unexposed circuit lines and exposed conductive traces may be employed in forming one or more tamper-detection networks, with the exposed conductive traces located only in the connection region to provide the enhanced tamper-detection capability disclosed herein in areas susceptible to mechanical and / or chemical attack on the adhesive.

[0133] Fig. Figure 21C illustrates a potential attack 2130 that can be prevented by the improved tamper-responsive assembly of Fig.21A & 21B. In particular, an attack 2130 through the structure 2101 into the adhesive 2115 may be attempted, wherein the attack involves a chemical attack on the adhesive to, for example, separate the inner major surface tamper-responsive sensor 1520' from the inner major surface tamper-responsive sensor 1510' and / or from the inner major surface of the structure 2101.By providing one or more conductive traces 2120, 2120', as illustrated, the conductive traces 2120, 2120' will also be wetted or otherwise damaged by any chemical attack on the adhesive 2115, wherein the damage to the conductive traces facilitates detection of the chemical attack by the monitoring circuitry and thus initiation of an alarm and / or triggering erasure of, for example, encryption / decryption keys stored within the secure space.

[0134] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It is further understood that the terms "comprise" (and any form of comprise, such as "comprises" and "having"), "possess" (and any form of possess, such as "possesses" and "possessing"), "include" (and any form of include, such as "includes" and "containing"), and "contain" (and any form of contain, such as "contains" and "containing") are open copular verbs.As a result, a method or entity that "comprises," "has," "includes," or "contains" one or more steps or elements has those one or more steps or elements, but is not limited to having only those one or more steps or elements. Similarly, a step of a method or an element of an entity that "comprises," "has," "includes," or "contains" one or more features has those one or more features, but is not limited to having only those one or more features. Furthermore, an entity or structure that is configured in a particular way is configured in at least that way, but may also be configured in ways not listed.

[0135] The corresponding structures, materials, acts, and equivalents of all means or step-plus-function elements in the following claims are intended to include any structure, material, or act for performing the function in combination with other claimed elements as expressly claimed. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the invention.The embodiment was chosen and described in order to best explain the principles of one or more aspects of the invention and the practical application, and to enable others skilled in the art to understand one or more aspects of the invention for various embodiments with various modifications as are suited to the contemplated use.

Claims

[1] Tamper-responsive assembly (600; 800; 1500; 2100) comprising: a tamper-responsive sensor (500; 605; 610, 611, 612; 811, 821; 821, 822; 1200; 1510, 1520; 1510', 1520'), the tamper-responsive sensor comprising: at least one shaped, flexible layer (510; 1700) having a first side (511; 1701) and a second side (512; 1702) opposite the first side, wherein the at least one shaped, flexible layer has surface curvatures (513) extending from the first side and surface curvatures (513) extending from the second side, wherein the at least one shaped, flexible layer is folded together as at least one flattened, folded-over layer; and Circuit lines (501; 1705) forming at least one resistance network, wherein the circuit lines are arranged on the first side and / or the second side of the at least one shaped, flexible layer, wherein the circuit lines are at least partially wrapped around the surface curvatures extending from the at least one of the first side or the second side of the at least one shaped, flexible layer. [2] The tamper-responsive assembly of claim 1, wherein a transverse cross-section of a flattened, folded layer of the at least one flattened, folded layer vertically intersects a common surface of the flattened, folded layer with the circuit lines forming the at least one resistor network a plurality of times. [3] The tamper-responsive assembly of claim 1, wherein the tamper-responsive sensor comprises a stack of layers, wherein the at least one flattened, folded layer is at least one layer of the stack of layers, and wherein the stack of layers further comprises at least one other layer (520, 521, 522) overlying at least one side of the at least one flattened, folded layer. [4] The tamper-responsive assembly of claim 3, wherein the at least one other layer of the stack of layers comprises at least one other flexible layer overlying at least one side of the at least one flattened, folded layer. [5] The tamper-responsive assembly of claim 3, wherein the at least one other layer of the stack of layers comprises at least one frangible layer (521) overlying at least one side of the at least one flattened, folded layer. [6] The tamper-responsive assembly of claim 1, wherein the tamper-responsive sensor comprises a stack of layers, the stack of layers comprising a plurality of shaped flexible layers each having circuit lines forming at least one respective resistive network disposed on at least one of the first and second sides thereof, the at least one shaped flexible layer being at least one shaped flexible layer of the plurality of shaped flexible layers. [7] The tamper-evident assembly of claim 1, wherein the tamper-evident sensor comprises a plurality of shaped flexible layers each having opposing first and second sides, and circuit lines forming at least one resistive network disposed on at least one of the first and second sides thereof, wherein the at least one shaped flexible layer is at least one shaped flexible layer of the plurality of shaped flexible layers, and wherein the plurality of shaped flexible layers are separate, discrete, shaped flexible layers positioned at least partially around an electronic assembly package (601; 1400) to be secured, wherein at least two shaped flexible layers of the plurality of shaped flexible layers overlap where they are adjacent to one another along the electronic assembly package. [8] The tamper-responsive assembly of claim 7, wherein the plurality of flexible molded layers comprises a plurality of flattened, folded layers each having respective circuit lines forming at least one respective resistor network. [9] The tamper-responsive assembly of claim 1, further comprising an electronics housing attached to a multilayer circuit board, and wherein the multilayer circuit board includes an integrated tamper-responsive sensor within the multilayer circuit board, the tamper-responsive sensor and the integrated tamper-responsive sensor together defining a secure space (801) between the electronics housing and the multilayer circuit board. [10] The tamper-responsive assembly of claim 9, wherein the at least one molded flexible layer having the circuit leads is attached to an inner surface of the electronics housing. [11] Component of an electronic assembly comprising: an electronic assembly (600; 800; 1500; 2100); an electronic assembly housing (601; 1400) which at least partially surrounds the electronic assembly; and a tamper-responsive electronic circuit structure associated with the electronic assembly package, the tamper-responsive electronic circuit structure comprising: a tamper-responsive sensor (500; 605; 610, 611, 612; 811, 821; 821, 822; 1200; 1510, 1520; 1510', 1520'), the tamper-responsive sensor comprising: at least one shaped, flexible layer (510; 1700) having a first side (511; 1701) and a second side (512; 1702) opposite the first side, wherein the at least one shaped, flexible layer has surface curvatures (513) extending from the first side and surface curvatures (513) extending from the second side, wherein the at least one shaped, flexible layer is folded together as at least one flattened, folded-over layer; and Circuit lines (501; 1705) forming at least one resistance network, wherein the circuit lines are arranged on the first side and / or the second side of the at least one shaped, flexible layer, wherein the circuit lines are at least partially wrapped around the surface curvatures extending from at least one of the first side or the second side of the at least one shaped, flexible layer. [12] The electronic assembly package of claim 11, wherein the tamper-responsive sensor comprises a plurality of shaped flexible layers each having opposing first and second sides, and circuit lines forming at least one resistive network disposed on at least one of the first and second sides thereof, wherein the at least one shaped flexible layer is at least one shaped flexible layer of the plurality of shaped flexible layers, and wherein the plurality of shaped flexible layers are separate, discrete shaped flexible layers positioned at least partially around the electronic assembly package, wherein at least two shaped flexible layers of the plurality of shaped flexible layers overlap where they are adjacent to one another along the electronic assembly package. [13] The electronic assembly package of claim 11, wherein the electronic assembly package is mounted on a multilayer printed circuit board, and wherein the tamper-responsive electronic circuit structure further comprises an integrated tamper-responsive sensor within the multilayer printed circuit board, the tamper-responsive sensor and the integrated tamper-responsive sensor together defining a secure space between the electronic assembly package and the multilayer printed circuit board. [14] Manufacturing process which comprises: Manufacturing a tamper-responsive assembly (600; 800; 1500; 2100), wherein the manufacturing comprises: Providing a tamper-responsive sensor (500; 605; 610, 611, 612; 811, 821; 821, 822; 1200; 1510, 1520; 1510', 1520'), wherein providing the tamper-responsive sensor comprises: Providing at least one shaped, flexible layer (510; 1700) having a first side (511; 1701) and a second side (512; 1702) opposite the first side, wherein the at least one shaped, flexible layer has surface curvatures (513) extending from the first side and surface curvatures (513) extending from the second side, wherein the at least one shaped, flexible layer is folded together as at least one flattened, folded-over layer; and Providing circuit lines (501; 1705) comprising at least one resistor network on the first side and / or the second side of the at least one shaped, flexible layer, wherein the circuit lines are at least partially wrapped around the surface curvatures extending from the at least one of the first side or the second side of the at least one shaped, flexible layer.

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