Identification unit with an unclonable structure

Abstract

Identification unit (100) with a uniquely characterized unclonable structure (101) by its impedance, which has a random arrangement of an electrical conductor (102) between two contact points (104), characterized in that the electrical conductor (102) electrically connects the two contact points (104) as a single, continuous electrical conductor (102) and its geometric course between the contact points (104) forms a random shape of a coil.

Description

[0001] The present invention relates to an identification unit with an unclonable structure comprising an electrical conductor randomly arranged between two contact points. State of the art

[0002] Product counterfeiting has always been a problem in the trade of goods, affecting both consumers and manufacturers of reputable products. Counterfeit products not only lead to lost sales but are also usually of lower quality than the original. This can result not only in financial losses for consumers but also in health risks, especially when safety-critical products such as spare parts or medications are involved.

[0003] Several methods for identifying products are already known, such as barcodes or RFID tags.

[0004] Barcodes are one of the most widely used methods of product identification, distinguished primarily by their cost-effectiveness and robustness. In particular, a barcode remains readable even if parts of it are illegible. However, barcodes are also particularly easy to duplicate.

[0005] RFID (Radio Frequency Identification) tags are electrical circuits that can communicate with an antenna via a high-frequency circuit. Passive RFID tags draw their power from a received radio frequency signal, while active RFID tags have their own battery. RFID tags can be simple memory chips or complex circuits with microcontrollers. The latter is significantly more secure against counterfeiting, but also considerably more expensive than simple barcodes.

[0006] Some well-known identification units contain a non-clonable structure; these include RFID tags. The non-clonable structure of an RFID tag consists of a memory that is at least partially non-rewritable.

[0007] An identification unit can then, for example, be attached to an object whose authenticity is to be guaranteed. By determining a value specified by the non-clonable structure, the product is thereby identified and authenticated.

[0008] The general approach to using so-called physically unclonable functions (PUFs) to prevent cloning involves generating a structure with a specific and unclonable random value, or finding a randomly distributed intrinsic property of the structure that can be authenticated. PUFs depend heavily on random processes, such as noise. Therefore, it is usually very easy to generate a PUF, but almost impossible to forge one. Variations in the manufacturing process lead to differing physical characteristics of a PUF.

[0009] WO 2007 / 072 251 A2 discloses a safety element in the form of an LC resonant circuit whose non-clonable property is based on the use of an inhomogeneous dielectric material that leads to a random, measurable capacitance.

[0010] The scientific publication “SREEDHAR, Aswin; KUNDU, Sandip: Physically unclonable functions for embedded security based on lithographic variation. In: 2011 Design, Automation & Test in Europe Conference, 14-18 March 2011, Grenoble, France, pp. 1-6. - ISBN 978-1-61284-208-0. URL: https: / / ieeexplore.ieee.org / document / 5763259 (accessed on 18.08.2025)” provides a general overview of PUFs whose function is based on unavoidable statistical variations in lithographic manufacturing processes of semiconductor structures.

[0011] DE 602 24 710 T2 shows a security element with a passivation structure in which particles are inhomogeneously distributed, resulting in a random impedance that depends on the application process and can be used for identification.

[0012] US 2010 / 0 327 856 A1 describes a safety device that uses a complex, grid-like arrangement of pseudo-randomly arranged conductor tracks to detect a change in impedance.

[0013] US 7 054 162 B2 discloses a security module that also uses a pseudorandom, but deterministically designed configuration of serial traces to form a unique signature.

[0014] EP 2 302 555 A2 relates to a method and a device for generating a digital signature from a PUF circuit, wherein the randomness is generated by inherent process variations in the manufacture of transistors.

[0015] However, all of the aforementioned identification methods have weaknesses regarding security and / or cost-effectiveness.

[0016] It is therefore desirable to provide an identification unit that improves both security and cost-effectiveness. Disclosure of the invention

[0017] According to the invention, an identification unit and a method for verifying such an identification unit are proposed, comprising the features of the independent claims. Advantageous embodiments are the subject of the dependent claims and the following description. Advantages of the invention

[0018] The invention makes it possible to provide an identification unit with relatively high counterfeit protection at a comparatively low cost. This is achieved by providing an identification unit with an unclonable structure containing an electrical conductor randomly arranged between two contact points. The arrangement of the electrical conductor follows no discernible pattern and is therefore impossible to clone or copy. For example, the wire can be positioned using an arm movable in the x and y directions, with the respective movements in the x and y directions being influenced by a random number generator. The random shape of the electrical conductor gives the unclonable structure a characteristic impedance. The resulting characteristic impedance of the identification unit will be referred to below as the PUF value. PUF stands for Physically Unclonable Function.

[0019] Preferably, the unclonable structure has randomly arranged metallic particles that further characterize the impedance and make copying even more difficult.

[0020] To protect the identification unit from environmental influences, it is advantageous to embed the non-clonable structure in a casing. Care must be taken to ensure that the two contact points of the electrical conductor are not insulated by the casing, so that they remain easily accessible to a reader. If the impedance of the non-clonable structure is not to be further affected by the casing, it is recommended that the casing be made of a non-metallic material. Plastics, such as resins, are particularly suitable for this purpose. In this case, it is further advantageous to create a random arrangement of metallic particles within the plastic, especially resin, casing. This allows for a particularly simple manufacturing process if the metallic particles are introduced into the casing before the resin has cured. This also ensures the permanent fixation of the non-clonable structure.

[0021] Depending on the application of the identification unit, it can also be advantageous to form the non-clonable structure between two metallic shielding plates. This protects the non-clonable structure from electromagnetic fields as well as mechanical or other environmental influences.

[0022] It is particularly advantageous if the identification unit includes an information medium that contains at least one retrievable target value of the impedance of the unclonable structure. In particular, several pairs of an impedance value and a corresponding frequency can be provided. Since impedance is known to be frequency-dependent, an information medium with multiple impedance / frequency pairs also allows the identification unit to be verified at several frequencies. The impedance value of the unclonable structure can also be expressed as a function of frequency by a function Z(f) in the information medium. The impedance value of the identification unit can then be determined at several frequencies, thus increasing its reliability.If at least one impedance target value is stored in the identification unit's information medium, all information necessary for verification is always available, and it is not necessary to connect to a database, especially an online database, that lists all target values. Setting up and maintaining such a database involves effort and infrastructure costs. It is particularly advantageous to use a device for verifying identification units that can read the information medium using a target value readout device.

[0023] The information medium can, for example, include text, a diagram, or a pattern, such as a two-dimensional or three-dimensional pattern (e.g., a barcode or QR (Quick Response) code). This allows at least one target impedance value to be read for verification of the identification unit. These are particularly easy-to-produce and read information media.

[0024] However, depending on the application area of ​​the identification unit, it can also be advantageous to store at least one target value of the impedance in a database.

[0025] The security of an identification unit can be further improved if the identification unit's information medium contains a digital signature. This signature could, for example, encode proof of origin, which is then verified by the device used to check the identification unit. Alternatively, information contained in the information medium could be digitally signed, as is common practice in information technology.

[0026] Since an identification unit according to the invention is particularly secure and at the same time particularly inexpensive to manufacture, it is advantageous to equip mass-produced goods, such as identification documents, access devices, means of payment, or the like, with an identification unit. These can be, for example, tickets for means of transport, admission tickets, tokens, or even identity cards or passports.

[0027] Regarding the method according to the invention, reference is made to the above statements, which are equally valid for the method.

[0028] It can be particularly useful to destroy an identification unit after verification. If the authenticity of an identification unit has been established, this can prevent its reuse, for example, if it is used in an access control or payment device. If a counterfeit identification unit has been detected, destroying it prevents a user from attempting to use it again. This can be achieved, for example, by melting the electrical conductor with a high current, thus interrupting it. Alternatively, the identification unit can be destroyed mechanically, for example, by punching holes in it or cutting it.

[0029] To verify the authenticity of an identification unit, a verification device may be provided. For this purpose, the verification device includes an impedance measuring device in a circuit. The circuit has two terminals for connecting the two contact points, an ohmic resistor, and an AC power source, which is preferably frequency-variable. The impedance measuring device comprises frequency measuring instruments, voltage measuring instruments, a phase detector, and a processing unit.

[0030] The processing unit is designed to calculate the impedance from the measured quantities. To calculate the impedance, the RMS values ​​of voltage and current, as well as the phase shift between voltage and current, are measured at a specific frequency. To verify the calculated impedance value, the frequency at which the impedance measurement was taken must be known. Frequency measuring instruments are provided for this purpose.

[0031] It is particularly advantageous if the AC power source is designed to provide alternating current at different frequencies.

[0032] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawing.

[0033] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations specified, but also in other combinations or on their own, without leaving the scope of the present invention.

[0034] The invention is schematically illustrated in the drawing using an exemplary embodiment and is described in detail below with reference to the drawing. Brief description of the drawings Fig. Figure 1 shows an embodiment of an identification unit according to the invention without shielding plates in a schematic frontal view. Fig. Figure 2 shows an embodiment of an identification unit according to the invention with shielding plates in a schematic side view. Fig. Figure 3 shows a schematic arrangement of an embodiment of a verification device according to the invention for identifying an identification unit according to the invention. embodiment(s) of the invention

[0035] In Fig. Figure 1 shows a schematic frontal view of an identification unit 100 according to the invention. The identification unit 100 has a non-clonable structure 101, which in turn has a random arrangement of an electrical conductor 102 with two contact points 104. The non-clonable structure 101 further comprises randomly distributed metallic particles 108 and is embedded in a shell 106, here formed from cast (synthetic) resin. The shell serves to protect and permanently fix the electrical conductor 102 and the randomly distributed metallic particles.

[0036] In this embodiment, the electrical conductor 102 is designed as a lacquer-insulated wire. At its ends, the wire is connected to the two contact points 104. Between its ends, the wire resembles a randomly shaped coil. This coil may be wound in a coil-like fashion in certain sections. The shape of the wire, particularly its windings, characterizes its impedance and thus the impedance of the structure 101. To further influence the impedance of the non-clonable structure 101, the metallic particles 108 are randomly distributed within the sheath 106.

[0037] In Fig. 2 is the embodiment of the identification unit according to Fig. 1 shown from a 90° rotated viewpoint. Fig. Figure 2 shows that the electrical conductor 102 can be arranged relatively flat to ensure a compact design. This enables a compact design of the identification unit according to the invention. To protect the measurement of the impedance of the non-clonable structure 101 from external influences, such as electromagnetic fields, the identification unit has metal shielding plates 105 on two outer sides.

[0038] In Fig.Figure 3 schematically illustrates a preferred embodiment of a verification device according to the invention for verifying an identification unit. The verification device comprises an integrated circuit S and a processing unit 318 as an impedance measuring device, with which the impedance of an unclonable structure of an identification unit 100 can be determined. To compare the impedance value with at least one target value stored in an information medium 110 applied to the identification unit, here designed as a barcode, a barcode reader 320 is provided as a target value reading device, which is connected to the processing unit 318.

[0039] Circuit S includes an AC power source 304, which is configured to supply the contact points 104 of the identification unit 100 with alternating current at a specific (in particular, predefinable) frequency. Furthermore, circuit S contains two voltmeters 306, 310, a resistor 302, a frequency meter 308, and two terminals 309 to which the contact points 104 of the identification unit 100 are connected.

[0040] To determine the impedance, the computing unit 318 requires the quantities U eff , I eff , as well as the phase shift φ between voltage and current. U eff is determined by the voltmeter 306. From the difference between the voltages measured at the voltmeters 306 and 310 and the resistance R, the effective current is calculated. Ieff=(U306−U310) / R given. U 306 , U 310denotes the measured voltage on the corresponding measuring device.

[0041] Considering the potentially high frequency of the measured voltages, a complex high-frequency measurement and evaluation initially appears necessary. However, the impedance can also be determined from the peak values ​​and zeros, which are particularly easy and cost-effective to measure. The RMS values ​​can be easily calculated from the peak values, and the phase shift φ can be easily determined from the zeros.

[0042] The measurement signals are fed to an amplitude and phase detector 314, which conveniently detects peak values ​​and zeros of the measured voltages and feeds them to an analog-to-digital converter (ADC) 316, which finally converts the measured values ​​into digital quantities.

[0043] Simple amplitude and phase detectors are commercially available, e.g., the AD8302.

[0044] The magnitude |Z| of the impedance Z can be determined from |Z|=Ueff / Ieff calculate.

[0045] Together with the phase shift φ, the impedance Z can be determined from this: Z=|Z|exp(i φ) Finally, the computing unit 318 compares the calculated impedance with a target value read by the barcode reader 320.

[0046] If necessary, the impedance measurement can be performed at different frequency values ​​to achieve even greater system safety.

Claims

[1] Identification unit (100) with a uniquely characterized unclonable structure (101) by its impedance, which has a random arrangement of an electrical conductor (102) between two contact points (104), characterized by , that the electrical conductor (102) electrically connects the two contact points (104) as a single, continuous electrical conductor (102) and whose geometric course between the contact points (104) forms a random shape of a coil. [2] Identification unit according to claim 1, wherein the non-clonable structure (101) has a random arrangement of metallic particles (108). [3] Identification unit according to claim 1 or 2, wherein the non-clonable structure (101) is embedded in a shell (106). [4] Identification unit according to one of the preceding claims, comprising two metallic shielding plates (105) between which the non-clonable structure (101) is arranged. [5] Identification unit according to one of the preceding claims, comprising an information means (110) which contains at least one setpoint of the impedance of the unclonable structure that can be read out. [6] Identification unit according to claim 5, wherein the information means (110) comprises a text, a diagram and / or a pattern. [7] Identification unit according to claim 5 or 6, wherein the information means (110) is digitally signed. [8] Identification device, access device or payment device comprising an identification unit (100) according to any of the foregoing claims. [9] Method for verifying an identification unit (100) according to any one of claims 1 to 7, wherein at least one value of the impedance of the unclonable structure (101) is determined and compared with a target value and the authenticity of the identification unit (100) is inferred from the comparison. [10] Method according to claim 9, wherein the target value is read from the information means of the identification unit according to claim 5. [11] Method according to claim 9 or 10, wherein the target value is read from a database. [12] Method according to claim 9, 10 or 11, wherein the unclonable structure is automatically destroyed after comparison. [13] Method according to claim 12, wherein the electrical conductor (102) is interrupted to destroy the unclonable structure. [14] Computing unit configured to perform a method according to any one of claims 9 to 13.

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