Entropy source mounted substrate protection structure, and method for disassembling the entropy source mounted substrate protection structure.

Abstract

To provide an entropy source mounted board protection structure and a disassembly method of the same for protecting an entropy source mounted board from a right unauthorized person and grasping attacks by the right unauthorized person step by step.SOLUTION: A physical random number generation apparatus 1 that employs an entropy source mounted board protection structure, comprises: a main board 20 that is equipped with a pin header 21 for electrical connection with an entropy source mounting board 10 and utilizes random numbers generated by the entropy source mounting board 10; a break plate 40 that is located between the main board and the entropy source mounting board 10; an outer peripheral frame 30 that is fixed to the main board 20 to surround the space on the side of the pin header 21 of the main board 20; and an inner cover material 50 that closes the space on the opposite side of the main board 20 in the entropy source mounting board 10.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a technique for physically protecting a chip that generates random numbers from unauthorized persons.

Background Art

[0002] There are many scenarios where a random number generator that generates random numbers used for encryption or the like is used to control the execution of a computer program or improve security. As a method for generating random numbers using a physically occurring random phenomenon, for example, there is a method in which noise generated by a diode or thermal noise is detected by a sensor, and random numbers are generated based on the detection signal of the sensor. A random number generation chip for realizing this method is a chip in which a diode and a noise sensor are integrated and incorporated, and is called an "entropy source mounted substrate".

[0003] Now, a communication security device that applies an entropy source mounted substrate is manufactured by soldering the above-mentioned entropy source mounted substrate to a main substrate. Hereinafter, a device incorporating an entropy source mounted substrate is referred to as a "physical random number generation device". However, it is not allowed for an unauthorized person to access the entropy source mounted substrate itself incorporated in the physical random number generation device or to tamper with the entropy source mounted substrate.

[0004] For example, Patent Document 1 discloses a technique for protecting a memory chip that records (stores) confidential data from (communicative) access by unauthorized persons.

[0005] Furthermore, Patent Document 2 employs the following configuration as an anti-fraud measure that can effectively deal with fraudulent activities in gaming machines. Specifically, if a fraudulent player who intends to illegally alter the operation of the gaming machine attempts to remove the authentication cover in order to remove the authentication chip (entropy source mounted board), the wiring of the authentication chip (entropy source mounted board) is easily cut, rendering the authentication chip (entropy source mounted board) unable to perform authentication processing with the main CPU. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Special Publication No. 2007-535744 [Patent Document 2] Japanese Patent Publication No. 2007-089942 [Disclosure of the Invention] [Problems that the invention aims to solve]

[0007] If someone without legitimate authority attempts to access, tamper with, or steal an entropy source-equipped board from a physical random number generator, it will involve dismantling the device incorporating the entropy source-equipped board. The technology disclosed in Patent Document 2 only physically disconnects the information processing between the authentication chip (entropy source-equipped board) and the main CPU, and does not prevent the authentication chip (entropy source-equipped board) itself from being removed intact.

[0008] It would be desirable to be able to gradually understand the level of motivation (mental strength to achieve the objective) that motivated someone to attempt to access or tamper with an entropy source-equipped circuit board. This is because it would be useful for identifying the initial stages of fraudulent activity and issuing warnings, identifying perpetrators by linking with security systems, implementing measures to prevent recurrence, and developing advanced applications.

[0009] The problem that this invention aims to solve is to provide a technology that protects an entropy source-equipped substrate from unauthorized persons and that can detect unauthorized attacks in a stepwise manner. [Means for solving the problem]

[0010] (First invention) The first invention was, Entropy source mounted substrate (10), A main board (20) for utilizing random numbers generated by the entropy source mounting board (10), which is equipped with a pin header (21) for electrically connecting to the aforementioned entropy source mounting board (10), The break plate (40) is positioned between the entropy source mounting board (10) and the main board (20) without interfering with the electrical connection, by passing through the aforementioned pin header (21), An outer peripheral frame (30) is fixed to the main board (20) in order to enclose the space on the pin header (21) side of the main board (20), An inner cover material (50) for closing the space on the side of the entropy source mounting substrate (10) opposite to the main substrate (20), This relates to a protective structure for an entropy source-mounted substrate (see Figure 2). The break plate (40) is supported and fixed to the outer peripheral frame (30) such that a lower fixing space (25) is secured between it and the main substrate (20), and an upper fixing space (55) is secured between it and the inner cover material (50) (see Figure 4). The aforementioned lower fixing space (25) and upper fixing space (55) are solidified with thermosetting resin (80) to fix the break plate (40) and main substrate (20), and the entropy source mounting substrate (10) and inner cover material (50), respectively (see Figure 11).

[0011] (Explanation of terms) The entropy source mounting substrate (10) may be a single substrate (10) attached to a single main substrate (20), but as shown in other claims, multiple substrates may be attached to a single main substrate (20) (11, 12 in Figure 2).

[0012] The "thermosetting resin (80)" is an insulator that can expand (follow) the heat generated by the activity of the entropy source mounted on the substrate (10), and can dissipate the heat generated by the entropy source mounted on the substrate (10). Specifically, this includes urethane resin, epoxy resin, and silicone resin. Epoxy resin may have insufficient conformability, and silicone resin is expensive, so urethane resin is often used.

[0013] (action) After the break plate (40) is passed through the pin header (21) of the main board (20), the entropy source mounting board (10) is electrically connected to the pin header (21). As a result, the entropy source mounting board (10) is positioned on the pin header (21) side of the main board (20) with the break plate (40) in between. By fixing the outer frame (30) to the main board (20), the space on the pin header (21) side of the main board (20) is enclosed by the outer frame (30). Then, the space on the entropy source mounting board (10) opposite to the main board (20) is closed off by the inner cover material (50).

[0014] Thermosetting resin (80) is poured into the lower fixing space (25) and the upper fixing space (55) and allowed to solidify. The poured thermosetting resin (80) fixes the break plate (40) and the main substrate (20), and the entropy source mounting substrate (10) and the inner cover material (50), respectively.

[0015] Regarding the protection structure of the random number generation chip according to the present invention, when an unauthorized person attempts to tamper with the entropy source mounting substrate (10), first, they try to remove the inner cover material (50) from the outer peripheral frame (30). The inner cover material (50) is fixed to the entropy source mounting substrate (10) by the thermosetting resin (80) in the fixing upper space (55), and the entropy source mounting substrate (10) is fixed to the main substrate (20). Therefore, if one tries to remove the inner cover material (50) from the outer peripheral frame (30), the external force will be transmitted to the thermosetting resin (80) in the fixing upper space (55) and the entropy source mounting substrate (10), and there is a high possibility that the entropy source mounting substrate (10) will be damaged. If the entropy source mounting substrate (10) is damaged, the tampering act can be prevented.

[0016] Also, since the external force for trying to remove the inner cover material (50) from the outer peripheral frame (30) is also transmitted to the main substrate (20) through the break plate (40), there is also a high possibility that the main substrate (20) electrically connected to the entropy source mounting substrate (10) will be damaged. If the main substrate (20) is damaged, the tampering act will not be easy and it contributes to prevention.

[0017] (Variation 1 of the First Invention) The first invention may be formed as follows. That is, an outer cover material (60) that covers the opposite side of the inner cover material (50) where the break plate (40) is located is provided, and the outer cover material (60) is fixed using a double-sided tape (59) positioned between the outer cover material (60) and the inner cover material (50). (See Figure 13).

[0018] (Function) The outer cover material (60) is fixed using a double-sided tape (59) positioned between the outer cover material (60) and the inner cover material (50) so as to cover the opposite side of the inner cover material (50) where the break plate (40) is located.

[0019] (Variation 2 of the First Invention) The first invention may be formed as follows. That is, the entropy source-mounted substrate (10) is composed of two substrates, a first substrate (11) and a second substrate (12). The main substrate (20) is provided with a pin header (21) for electrically connecting to the first substrate (11) and the second substrate (12). At the central portion in the longitudinal direction of the break plate (40), two central standing portions (45) and a central horizontal portion (46) sandwiched between the two central standing portions (45) are provided to form a fixing central space (26) between the first substrate (11) and the second substrate (12). The thermosetting resin (80) solidifies the fixing central space (26).

[0020] (Term Explanation) Having two "first substrate (11) and second substrate (12)" has the following meanings. First, the speed of generating random numbers can be increased. Second, even if a defect (such as an electrical contact failure) occurs in one entropy source-mounted substrate and it becomes dysfunctional, random numbers can still be generated by the other. Therefore, it contributes to enhancing the reliability of the physical random number generator incorporating the invention of the present application.

[0021] (Function) By providing two central standing portions (45) and a central horizontal portion (46) sandwiched between the two central standing portions (45) at the central portion in the longitudinal direction of the break plate (40), a fixing central space (26) exists between the first substrate (11) and the second substrate (12). Since the fixing central space (26) is solidified by pouring the thermosetting resin (80), the connection between the break plate (40) and the main substrate (20) becomes stronger.

[0022] (Second Invention) The second invention relates to a method of disassembling the entropy source-mounted substrate protection structure corresponding to Variation 1 in the first invention. Here, the entropy source mounted substrate protection structure refers to the entropy source mounted substrate (10) and A main board (20) for utilizing random numbers generated by the entropy source mounting board (10), which is equipped with a pin header (21) for electrically connecting to the aforementioned entropy source mounting board (10), The break plate (40) is positioned between the entropy source mounting board (10) and the main board (20) without interfering with the electrical connection, by passing through the aforementioned pin header (21), An outer peripheral frame (30) is fixed to the main board (20) in order to enclose the space on the pin header (21) side of the main board (20), An inner cover material (50) for closing the space on the side of the entropy source mounting substrate (10) opposite to the main substrate (20), In addition to being equipped, The break plate (40) is supported and fixed to the outer peripheral frame (30) such that a lower fixing space (25) is secured between it and the main circuit board (20), and an upper fixing space (55) is secured between it and the inner cover material (50). The aforementioned lower fixing space (25) and upper fixing space (55) are solidified with thermosetting resin (80) to fix the break plate (40) and main substrate (20), and the entropy source mounting substrate (10) and inner cover material (50), respectively. The inner cover material (50) is provided with an outer cover material (60) that covers the opposite side of the inner cover material (50) from where the break plate (40) is located. The outer cover material (60) is fixed using double-sided tape (59) positioned between it and the inner cover material (50) in this entropy source mounting substrate protection structure. The method for disassembling the entropy source mounted substrate protection structure is a first step of removing the outer cover material (60) from the inner cover material (50), The second step is to remove the inner cover material (50) from the break plate (40), This method includes [something].

[0023] In the second step described above, the solidified thermosetting resin (80) protects some parts of the entropy source mounting substrate (10) while leaving others unprotected. As a result, the force attempting to decompose the substrate concentrates on the unprotected areas, often causing damage to the entropy source mounting substrate (10), making it difficult to remove the substrate (10) without damaging it.

[0024] (Third invention) The third invention also relates to a method for disassembling an entropy source mounted substrate protection structure, corresponding to variation 1 of the first invention, and the entropy source mounted substrate protection structure is the same as in the second invention. The method for disassembling the entropy source mounting substrate protection structure according to the third invention comprises a first step of removing the fixing points between the main substrate (20) and the outer peripheral frame (30), This method includes [something].

[0025] In the first step described above, the solidified thermosetting resin (80) protects some parts of the entropy source mounting substrate (10) while leaving others unprotected. As a result, the force attempting to decompose the substrate concentrates on the unprotected areas, often causing damage to the entropy source mounting substrate (10), making it difficult to remove the substrate (10) without damaging it.

[0026] The second and third inventions are intended to infringe the patent rights if the entropy source mounting substrate protection structure, which corresponds to Variation 1 of the first invention, is disassembled by an unauthorized person in the order of the first and second steps described above. [Effects of the Invention]

[0027] According to the first invention, we were able to provide an entropy source-mounted substrate protection structure that protects the entropy source-mounted substrate from unauthorized persons and allows for the gradual detection of attacks by unauthorized persons. According to the second and third inventions, we were able to provide a method for disassembling an entropy source-mounted substrate protection structure that protects the entropy source-mounted substrate from unauthorized persons and allows for the step-by-step detection of attacks by unauthorized persons. [Brief explanation of the drawing]

[0028] [Figure 1] This is a perspective view showing a physical random number generator according to an embodiment. [Figure 2] This is an assembled perspective view showing the main components of a physical random number generator according to an embodiment. [Figure 3] This is a plan view showing the outer cover material and inner cover material in a physical random number generator according to an embodiment. [Figure 4] This is a vertical cross-sectional view showing a physical random number generator according to an embodiment. [Figure 5] This is an assembly perspective view of the physical random number generator according to the embodiment, showing the integration of the break plate. [Figure 6] This is a perspective view showing the physical random number generator according to the embodiment with the break plate incorporated. [Figure 7] This is a side view of a physical random number generator according to an embodiment, centered on a resin spacer. [Figure 8] This is an assembly perspective view of the physical random number generator according to the embodiment, showing the process of incorporating the inner cover material. [Figure 9] These are perspective views (a) and side views (b) of a physical random number generator according to an embodiment, incorporating an inner cover material. [Figure 10] This is a perspective view showing the inner cover material of the physical random number generator according to the embodiment, before and after resin is added. [Figure 11] This is a cross-sectional view showing the resin that has been fed into the physical random number generator according to the embodiment. [Figure 12] This is an assembly perspective view of the physical random number generator according to the embodiment, showing the process of incorporating the outer cover material. [Figure 13] This is a partial cross-sectional view of the physical random number generator according to the embodiment, showing the assembled state (a) and the state when under attack (b). [Figure 14] This is a partial cross-sectional view of the physical random number generator according to the embodiment, showing the assembled state (a) and the state when under attack (b). [Figure 15] Figure 14 shows a partial cross-sectional view from a different direction than Figure 14, illustrating the assembled state (a) and the state when under attack (b). [Figure 16] This shows an enlarged cross-sectional view of the inner cover material of the physical random number generator according to the embodiment, in the event of an attack. [Figure 17] This shows an enlarged cross-sectional view of the inner cover material of the physical random number generator according to the embodiment, in the event of an attack. [Figure 18] This shows an enlarged cross-sectional view of the physical random number generator according to the embodiment, in the event of an attack on a soldered joint. [Figure 19] This figure shows an enlarged cross-sectional view from a different direction than Figure 18, illustrating the case where the solder joints of the physical random number generator according to the embodiment are attacked. [Figure 20] A block diagram showing the relationships between each component. [Figure 21] This is a cross-sectional view showing a physical random number generator with only one entropy source substrate, and it represents the state before resin is added. [Figure 22] This is an assembly perspective view showing combinations of entropy source-equipped substrates. It shows the state with two first substrates assembled (a) and the state with two second substrates assembled (b). [Modes for carrying out the invention]

[0029] The present invention will be described below based on embodiments. The drawings used herein are Figures 1 to 22. In the following, unless otherwise specified, the top of the page indicates the physically upward direction.

[0030] (Figure 1) Figure 1 is a perspective view showing a physical random number generator 1 according to an embodiment employing the entropy source mounted substrate protection structure according to the present invention. (a) and (b) show the state as viewed from different directions. This physical random number generator 1 comprises a main board 20, a rectangular outer frame 30 erected and fixed inside the outer periphery of the upper surface of the main board 20, and an outer cover material 60 fixed to cover the upper surface of the outer frame 30. An entropy source mounting substrate protection structure is provided in the space enclosed by the lower surface of the outer cover material 60, the inner surface of the outer frame 30, and the upper surface of the main board 20 (more precisely, the main board 20 and the outer frame 30 constitute the entropy source mounting substrate protection structure according to the present invention).

[0031] (Figure 2) Figure 2 is an assembled perspective view of the components that make up the physical random number generator 1 according to this embodiment. The top surface of the aforementioned main board 20 incorporates electronic circuits (not shown in the diagram), and numerous pin headers 21 are erected for connecting to these electronic circuits.

[0032] As mentioned above, the outer frame 30 is a rectangular frame that is erected and fixed inside the outer edge of the top surface of the main board 20, and its height is greater than the pin header 21 mentioned above. The outer frame 30 and the main board 20 are fixed together all around by soldering so that they cannot be easily separated.

[0033] The break plate 40 has an outermost horizontal portion 41 (see Figure 5) at both ends, which is placed on the upper end of the outer peripheral frame 30 in the short-side direction, and has a shape that is bent approximately 10 times. It is equipped with a header support portion 43 (see Figure 5) that supports the pin header 21 while passing through it, and when assembled it will be located above the main board 20. The fixing of the outer frame 30 and the break plate 40 will be explained using Figure 5.

[0034] The first substrate 11 and the second substrate 12, which constitute the entropy source mounting substrate 10, are located in the two spaces formed by the central horizontal section 46 (see Figure 5) of the break plate 40. Both the first substrate 11 and the second substrate 12 have a rectangular planar shape and are provided with through-holes along their long sides through which pin headers 21 are passed for electrical connection. By passing the pin headers 21 through these through-holes, the first substrate 11 and the second substrate 12 are electrically connected to the main substrate 20, even though they are separated by the break plate 40.

[0035] In this invention, the entropy source mounting substrate 10 may be one or more (although the illustrated examples are omitted, it may be three or more), but in this embodiment, the chip style is standardized to have through-holes through which the pin header 21 is electrically connected, and the entropy source mounting substrate 10 employs two chips (first substrate 11 and second substrate 12). The reason for this is as follows.

[0036] Firstly, it is possible to mount two entropy source boards of the same or different types. In this case, it contributes to improving the reliability of the output random numbers (see Figure 22). For example, even if one entropy source board fails, random numbers can still be generated if the other entropy source board is functioning correctly. Furthermore, the physical random number generator 1 according to this embodiment can function even if only one entropy source-equipped substrate is incorporated. Therefore, even if entropy source-equipped substrates become difficult to obtain, this contributes to stabilizing the supply of the physical random number generator 1 in response to demand.

[0037] Secondly, even if one entropy source-equipped board is tampered with by someone without legitimate authority, security can be ensured because it is possible to generate random numbers that eliminate the intent of tampering by performing calculations with random numbers generated by other entropy source-equipped boards.

[0038] Thirdly, by mounting two identical entropy source boards, it becomes possible to process random number generation in parallel, thereby doubling the generation speed.

[0039] After assembling the entropy source mounting board 10 onto the break plate 40, the inner cover material 50 is fixed onto the break plate 40. Then, after resin injection (see Figure 10), the outer cover material 60 is fixed in place.

[0040] (Figure 3) Figure 3 is a plan view showing the positions of the double-sided tape to be attached to the lower surface of the outer cover material 60 and the lower surface of the inner cover material 50. Double-sided tape 59 is applied to the underside of the outer cover material 60 in a frame shape, excluding the central part. Double-sided tapes 48, 49, and 49 are attached to the lower surface of the inner cover material 50 at the center and ends in the long direction.

[0041] (Figure 4) Figure 4 is a longitudinal cross-sectional view showing the spaces that exist when each component is assembled. In the figure, spaces are indicated by underlining the component numbers. The resin shown in Figure 10 will be poured into and flow into the spaces shown in this figure.

[0042] Between the lower surfaces of the first substrate 11 and the second substrate 12, and the upper surface of the break plate 40, there are spaces 15, 15 beneath the substrates on which the entropy source is mounted. Furthermore, there are fixing lower spaces 25, 25 between the lower surface of the break plate 40 on which the first substrate 11 and the second substrate 12 are located and the upper surface of the main substrate 20.

[0043] The space enclosed by the inside of the outer frame 30, the top surface of the main board 20, and the bottom surface of the break plate 40 contains fixing side spaces 27, 27. A central fixing space 26 exists in the space sandwiched between the first substrate 11 and the second substrate 12, and enclosed by the upper surface of the main substrate 20 and the lower surface of the break plate 40.

[0044] There are upper fixing spaces 55, 55 between the upper surfaces of the first substrate 11 and the second substrate 12 and the lower surface of the inner cover material 50. Furthermore, a central upper space 65 exists between the upper surface of the inner cover material 50 and the lower surface of the outer cover material 60.

[0045] (Figure 5) Figure 5 shows the state in which the break plate 40 shown in (a) is incorporated into the main board 20 to which the outer frame 30 is fixed, as shown in (b) when the first board 11 and the second board 12 are assembled.

[0046] The upper part of the outer surface of the outer frame 30 is provided with fixing projections 31 for securing it to the break plate 40. The upper end of the outer frame 30 is provided with a horizontal bent portion 32 that is bent inward. An opening 34 is provided at the corner of the horizontal bent portion 32, into which the outermost vertical portion 42C of the break plate 40 is inserted.

[0047] The break plate 40 is formed by folding a rectangular thin plate as follows: it comprises the outermost horizontal portions 41, 41 at both ends in the direction of the long side, the outermost vertical portions 42C, 42C folded downward from the outermost horizontal portions 41, 41 in the opposite direction to the outermost vertical portion 42, the outermost vertical portions 42, 42 folded downward from the outermost horizontal portions 41, 41, the entropy source mounting substrate support portions 44, 44 folded horizontally from the outermost vertical portions 42, 42, the central vertical portions 45, 45 folded upward from the entropy source mounting substrate support portions 44, 44, and the central horizontal portion 46 which is sandwiched between the central vertical portions 45, 45 and forms a horizontal plane.

[0048] Double-sided tapes 48 and 49 are attached to the areas where the lower surface of each outermost horizontal section 41 contacts the outer peripheral frame 30 for fixing to the outer peripheral frame 30 (see Figure 8). Each entropy source mounting board support section 44 is provided with header support sections 43 on both sides to guide the pin header 21, which is erected upward from the main board 20, through it.

[0049] Near the upper ends of each outermost upright portion 42, there are oval-shaped through holes 42B for fixing the cover, with the horizontal direction as the longitudinal direction. These cover fixing holes 42B are through which fixing wedges 57A, provided on the inner cover material 50 side, pass in order to fix the inner cover material 50 (see Figure 8). Furthermore, circular and oval through-holes 42A are provided below the cover fixing hole 42B. These through-holes 42A function to allow the resin, which is introduced at the stage shown in Figure 10, to flow into the fixing side space 27 shown in Figure 4.

[0050] Each central upright section 45 is provided with a vertical groove 45A, which is a vertical groove with a convex side facing the central horizontal section 46. This vertical groove 45A functions to allow the resin introduced at the stage shown in Figure 10 to flow into the space 15 below the entropy source mounted substrate and the fixing space 25 shown in Figure 4.

[0051] A circular through-hole 46A is provided in the central horizontal section 46. This through-hole 46A functions to allow the resin, which is introduced at the stage shown in Figure 10, to flow into the space 15 below the entropy source mounting substrate and the central fixing space 26 shown in Figure 4.

[0052] (Figure 6) Figure 6 shows the state after the break plate 40 has been assembled onto the main board 20 to which the outer frame 30 is fixed, and the first board 11 and the second board 12 have been assembled. The through holes 42A, 46A and vertical grooves 45A, which are provided for pouring the resin, also serve to release any air bubbles trapped in the poured resin upwards (above the inner cover material 50).

[0053] (Figure 7) Figure 7 shows that resin spacers 29 are present between the pin header 21 and the break plate 40, more specifically between the upper surface of the main substrate 20 and the lower surface of the break plate 40, and between the lower surfaces of the first substrate 11 and the second substrate 12 and the upper surface of the break plate 40.

[0054] The break plate 40 has the complex shape described above and is equipped with various through holes, so it is reasonable to manufacture it by bending or punching out a metal plate. However, if it is made of metal, it is necessary to insulate it from the pin header 21, so the resin spacer 29 is used to electrically isolate it.

[0055] (Figure 8) Figure 8 shows the state in which the inner cover material 50 is fixed to each component in the state shown in Figure 6. Double-sided tape 49 is attached to the upper surface of the outermost horizontal section 41 of the break plate 40. Double-sided tape 48 is also attached to the upper surface of the central horizontal section 46.

[0056] The inner cover material 50 comprises an upper frame 51 which is a generally rectangular plate-like body, and an outermost upright portion 52 which is erected from near the outer circumference of the lower surface of the upper frame 51. Inclined frames 53 that incline downward are extended from both ends in the longitudinal direction of the upper frame 51, and a central horizontal portion 54 that forms a horizontal plane is located between both inclined frames 53.

[0057] The outermost upright portion 52 is provided with a through hole 52A. This through hole 52A is positioned to coincide with a fixing projection 31 that is provided on the upper outer circumference of the outer frame 30 so as to protrude outward. The insert frame 57 is also provided with a fixing wedge 57A that engages with the break plate 40.

[0058] A rectangular through-hole, or air vent hole 51A, is provided between the outer circumference of the short side of the upper frame 51 and the inclined frame 53. This air vent hole 51A serves to allow the resin shown in Figure 10 to be introduced and to remove any air bubbles contained in the incoming resin.

[0059] In the inclined frame 53, a resin inlet 53A is provided in the area surrounded by the air vent 51A and the central horizontal section 54. The resin shown in Figure 10 is to be introduced through this resin inlet 53A.

[0060] (Figure 9) Figure 9 is a diagram showing how the outer frame 30, break plate 40, and inner cover material 50 are fixed to each other. Figure 9(b) is the BB cross section in the perspective view of Figure 9(a).

[0061] The upper end of the outer peripheral frame 30 in the short-side direction is bent inward to form a bent horizontal section (see Figure 5, bent horizontal section 32), on which the outermost horizontal section 41 of the break plate 40 is placed.

[0062] The double-sided tape 49 attached to the upper surface of the outermost horizontal portion 41 of the break plate 40 secures it to the lower surface of the inner cover material 50. In addition, the cover fixing hole 42B provided in the outermost vertical portion (see Figure 5, outermost vertical portion 42) of the break plate 40 engages with the fixing wedge 57A of the inner cover material 50.

[0063] The fixing projections 31 of the outer frame 30 are fitted into the fixing holes 52A of the inner cover material 50, thereby fixing the outer frame 30 and the inner cover material 50 together. As a result, the outer frame 30, the break plate 40, and the inner cover material 50 are fixed to each other.

[0064] (Figure 10) Figure 10 shows the resin 80 being poured into the inner cover material 50 from above by the resin pouring machine 70 before and after the process. As shown in Figure 10(a), the resin is poured in from above the resin inlet 53A or through-hole 54A in the inner cover material 50. Then, the resin is poured in until the through-hole 54A is covered with resin 80 (the upper fixing space 55 and resin reservoir space 56 shown in Figure 11 are filled).

[0065] The resin 80 used for injection is a thermosetting resin. The reason for using a thermosetting resin is to avoid damaging the first substrate 11 and the second substrate 12 by allowing them to expand as they heat up during their activity.

[0066] The type of resin used for the injection must be an insulator, capable of expanding (following) the heat generated by the activity of the entropy source mounted on the substrate 10, and capable of dissipating the heat generated by the entropy source mounted on the substrate 10. In this embodiment, urethane resin was used.

[0067] (Figure 11) Figure 11 shows which spaces the resin introduced by the resin dispenser 70 shown in Figure 10 fills.

[0068] The resin 80, passing from the resin reservoir space 56 through the through hole 54A, fills the central fixing space 26.

[0069] The resin 80, passing from the resin reservoir space 56 through the resin input port 53A, fills the upper fixing space 55. It then passes through the vertical groove 45A of the break plate 40 (see Figure 5) to fill the space 15 below the entropy source mounting substrate and the lower fixing space 25. A portion of the resin that reaches the upper fixing space 55 also fills the side fixing space 27 via the through hole 42A of the break plate 40.

[0070] (Figure 12) Figure 12 shows how the outer cover material 60 is fixed after the resin 80 has filled the various spaces, as shown in Figure 11. Double-sided tape 59 is attached to the upper surface of the inner cover material 50, and the outer cover material 60 is secured with the double-sided tape 59.

[0071] (Figure 13) Figure 13(a) shows the relationship between the outer cover material 60 and inner cover material 50 shown in Figure 12, as well as the outer frame 30 and the break plate 40. The side portion 62, which is bent downward from the outer peripheral end of the upper portion 61 of the outer cover material 60, has a folded-over portion 62A at its end that is slightly bent inward and covers the lower end of the inner cover material 50.

[0072] Figure 13(b) shows an example where, in the fixed state shown in Figure 13(a), an unauthorized person attempts to remove the outer cover material 60 by inserting the tip of a flathead screwdriver or the like into the small gap between the folded portion 62A and the outer frame 30. Due to the presence of the double-sided tape 59, the outer cover material 60 often deforms so that the upper end portion 61A lifts up.

[0073] (Figure 14) Figure 14(a) shows the state after the outer cover material 60 has been removed by the attack shown in Figure 13(b).

[0074] Figure 14(b) shows a case where the inner cover material 50 is subjected to further attack by an unauthorized person after the outer cover material 60 has been removed. Due to the presence of the double-sided tape 49, the outer periphery of the inner cover material 50 is often deformed in a way that causes it to lift.

[0075] (Figure 15) Figure 15(a) shows the same state as in Figure 14(a) viewed from a different direction. Furthermore, Figure 15(b) shows the case where the inner cover material 50 is attacked from a different direction in the state shown in Figure 14(b).

[0076] (Figure 16) Figure 16 shows the case where the inner cover material 50 is subjected to stress strong enough to peel off the double-sided tape 49. The fixing wedge 57A is about to come out of the cover fixing hole 42B. When subjected to such stress, a gap is created between the resin spacer 29 located below the break plate 40 and the break plate 40, and the aforementioned stress is transmitted in such a way that it cracks the entropy source mounting substrate 10.

[0077] (Figure 17) Figure 17 shows how the entropy source mounting substrate 10 (second substrate 12 in the figure) is affected via the break plate 40 when subjected to an attack as shown in Figure 16. The break plate 40 deforms, and stress is applied to the inner portion of the pin header 21 on the entropy source mounting substrate 10 (second substrate 12), which has a small thickness dimension, and in most cases the entropy source mounting substrate 10 (second substrate 12) is destroyed.

[0078] Furthermore, multiple plate fixing protrusions 33 are provided on the inner side of the short side of the outer frame 30. These plate fixing protrusions 33 fit into through holes provided at corresponding locations (not shown) in the break plate 40, thereby fixing the outer frame 30 and the break plate 40 together.

[0079] (Figure 18) Figure 18(a) shows what happens when an unauthorized person attacks the solder joint between the main board 20 and the short side portion of the outer frame 30. As shown in Figure 18(b), the break plate 40 deforms, and stress is applied to a small area in the thickness direction, namely the inner portion of the pin header 21 on the entropy source mounting substrate 10 (second substrate 12). In this figure, the resin 80 is omitted, but in most cases, the entropy source mounting substrate 10 (second substrate 12) will be destroyed.

[0080] (Figure 19) Figure 19(a) shows what happens when an unauthorized person attacks the solder joint between the main board 20 and the long side portion of the outer frame 30. As shown in Figure 19(b), the fixing wedge 57A is about to come loose from the cover fixing hole 42B. When subjected to such stress, a gap is created between the resin spacer 29 located below the break plate 40 and the break plate 40, and the aforementioned stress is transmitted in such a way that it cracks the entropy source mounting substrate 10.

[0081] (Figure 20) Figure 20 shows the relationship between the entropy source mounting substrate 10, the main substrate 20, the pin header 21, the outer frame 30, the break plate 40, the inner cover material 50, and the outer cover material 60, and how they are fixed together.

[0082] (Figure 21) Figure 21 is a cross-sectional view showing a physical random number generator with only one entropy source mounted on a substrate 10, and shows the state before resin is added. In a physical random number generator equipped with one entropy source-mounted substrate 10, the basic structure is as shown in Figure 2, with the main substrate 20, outer frame 30, and break plate 40 stacked in that order, and the entropy source-mounted substrate 10 set on the break plate 40 through which a pin header 21 protruding upward from the main substrate 20 passes.

[0083] An inner cover material 50, fixed to the break plate 40 and the outer frame 30, covers the top of the entropy source mounting substrate 10. With the inner cover material 50 fixed, resin 80 is poured in from the resin input port 53A and fills the fixing lower space 25, fixing side space 27, the space 15 below the entropy source mounting substrate, the fixing upper space 55, and the resin reservoir 56 (since there is only one entropy source mounting substrate 10, the fixing central space 25 does not exist). The inner cover material 50 is fixed to an outer cover material 60 which is fixed to the outer frame 30 of the inner cover material 50.

[0084] The entropy source-mounted substrate protection structure configured as described above will also be destroyed if attacked by an unauthorized person, resulting in the state shown in Figures 13-19.

[0085] Furthermore, if the attempt to tamper with the entropy source mounted on the circuit board 10 was abandoned at the stage of attempting to remove the outer cover material 60 from the inner cover material 50, then there should be some scratches or deformation somewhere on the folded portion 62A and the outer frame 30. If the attempt to tamper with the entropy source mounted on the substrate 10 was abandoned at the stage of removing the outer cover material 60 from the inner cover material 50 and attempting to remove the inner cover material 50 from the outer frame 30, then one of the outer peripheral parts of the inner cover material 50 should be deformed, or the fixing protrusions 31 of the outer frame 30 should be exposed. As described above, when the entropy source-mounted substrate protection structure according to the present invention is adopted, traces of an unauthorized attack can be identified in a step-by-step manner after the fact. [Industrial applicability]

[0086] The present invention has applicability in industries such as the manufacturing of information and communication equipment, the information and communication service industry including the installation of information and communication equipment, and the software industry that creates computer software for information and communication services. [Explanation of Symbols]

[0087] 1; Physical random number generator 10; Entropy source mounted substrate (entropy source) 11; first board 12;Second board 15; Space beneath the substrate with the entropy source mounted 20; Main board 21; Pin Header 25 ; Lower space for fixing 26; Central space for fixation 27 ; Side space for fixing 29; Resin spacer 30; outer frame 31 ;Fixing protrusion 32; Horizontal folding section 33; Plate fixing protrusions 34; opening 40; Break Plate 41; outermost horizontal part 42;Outermost standing part 42A;Through hole 42B; Hole for fixing the cover 42C; Outermost vertical part 43; Header support section 44; Entropy source mounted substrate support section 45; Central vertical section 45A; Vertical groove 46 ;Central horizontal part 46A;Through hole 48; Double-sided tape (center) 49; Double-sided tape (side) 50; Inner cover material 51; Top frame 51A; Air vent 52;Outermost standing part 52A;Fixing hole 53; Inclined frame 53A; Resin input port 54;Central horizontal part 54A;Through hole 55 ; Upper space for fixing 56; Resin accumulation space 57; Insert frame 57A; Fixing wedge 59: Double-sided tape 60; Outer cover material 61;Top part 61A;Top end part 62; Side section 62A; Folded end 65; upper central space 70 ;Resin feeding machine 80; resin

Claims

1. Entropy source mounted substrate, A main board for utilizing random numbers generated by the entropy source board, which is equipped with pin headers for electrically connecting to the aforementioned entropy source board, A break plate is positioned between the aforementioned entropy source mounting board and the aforementioned main board, without interfering with the electrical connection to the aforementioned main board, by passing through the aforementioned pin header, An outer frame fixed to the main board in order to enclose the space on the pin header side of the main board, An inner cover material for closing the space on the side of the entropy source mounting substrate opposite to the main substrate, An entropy source mounted substrate protection structure comprising, The aforementioned break plate is supported and fixed to the outer peripheral frame such that it secures a lower space for fixing between it and the main circuit board, and also secures an upper space for fixing between it and the inner cover material. The aforementioned lower and upper fixing spaces are solidified with thermosetting resin to fix the break plate and main substrate, and the entropy source mounting substrate and inner cover material, respectively. Entropy source mounted substrate protection structure.

2. The inner cover material is provided with an outer cover material that covers the opposite side of the inner cover material from where the break plate is located. The outer cover material was to be fixed in place using double-sided tape positioned between it and the inner cover material. The entropy source mounted substrate protection structure according to claim 1.

3. The aforementioned entropy source mounting substrate consists of two substrates: a first substrate and a second substrate. The aforementioned pin header is to be electrically connected to the first substrate and the second substrate. In the longitudinal center of the aforementioned break plate, two central upright sections and a central horizontal section sandwiched between the two central upright sections are provided in order to create a central fixing space between the first substrate and the second substrate. The aforementioned thermosetting resin also solidifies the aforementioned central space for fixing. The entropy source mounted substrate protection structure according to either claim 1 or claim 2.

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