Title of Invention: AUTHENTICITY DETERMINATION DEVICE, AND AUTHENTICITY DETERMINATION METHOD
Technical Field
[0001] The present invention relates to an authenticity determination device that determines whether a device is an authentic product or a counterfeit product. Background Art
[0002] With the development of device manufacturing technology, it has become relatively easy to manufacture counterfeit products made to look like authentic devices. Thus, the importance of authenticity determination technology for distinguishing between authentic products and counterfeit products is increasing. PUF (Physical Unclonable Function) technology has been proposed as one of techniques that can be used for authenticity determination. In the PUF technology, by using the fact that manufacturing variations always exist even in exactly the same circuits manufactured with the same design, it is possible to generate, from exactly the same circuits, a different value for each individual integrated circuit chip on which each circuit is mounted. Furthermore, since these manufacturing variations are difficult to artificially control or duplicate, they are effective for preventing manufacture of counterfeit products made to look like authentic products. Patent Literature 1 discloses a method of preventing duplication of circuits and realizing secure authentication by using an integrated circuit that restores secret information by utilizing the PUF technology. Citation List Patent Literature

[0003] Patent Literature 1: JP 2010-226603 A Summary of Invention Technical Problem
[0004] The method of Patent Literature 1 provides a function of preventing duplication of integrated circuits by recognizing that a duplicated product is not an authentic product if an authentic integrated circuit is duplicated. However, it is not possible to detect imitation of a device including an integrated circuit in the case of a device in which an authentic integrated circuit is used and parts other than the authentic integrated circuit are made of different duplicated products. Therefore, for example, there has been a problem that it is impossible to prevent fraudulence such as obtaining an inexpensive device legitimately, reconfiguring only its appearance to make it look like an expensive device, and reselling it as the expensive device. [0005] The present invention has been made to solve the above problem, and aims to realize an authenticity determination device that makes it difficult to manufacture a counterfeit product using parts of an authentic product by performing verification using device information specific to a device and concerning the entirety of the device including an integrated circuit. Solution to Problem
[0006] In order to solve the above-described problem, an authenticity determination device according to the present invention includes a device information storage unit to store device information indicating information specific to a determination target device, authenticity of which is to be determined; a signature storage unit to store a signature for the device information; a key information storage unit to store key information being information for deriving a verification key corresponding to a generation key with which the signature has been generated; a verification key derivation unit to derive the

verification key by using the key information; a signature verification unit to verify
validity of a combination of the device information and the signature by using the
verification key derived by the verification key derivation unit; and a determination unit
to determine the authenticity of the determination target device, based on the validity
verified by the signature verification unit.
Advantageous Effects of Invention
[0007] According to the present invention, it is possible to obtain an effect of making
it difficult to manufacture a counterfeit product using parts of an authentic product by
performing verification using information specific to a device and concerning the
entirety of the device including an integrated circuit.
Brief Description of Drawings
[0008] Fig. 1 is a diagram illustrating a configuration when an authenticity
determination device according to a first embodiment is applied to a determination
target device;
Fig. 2 is a diagram illustrating an example configuration of the authenticity determination device according to the first embodiment;
Fig. 3 is a diagram illustrating an example of a hardware configuration of an authenticity determination device 1;
Fig. 4 is a diagram illustrating an example configuration of a determination information registration device 3 according to the first embodiment;
Fig. 5 is a diagram illustrating an example of a hardware configuration of the determination information registration device 3;
Fig. 6 is a diagram illustrating an example of device information stored in a device information storage unit 25;
Fig. 7 is a flowchart illustrating a flow of the operation of the determination

information registration device 3 according to the first embodiment;
Fig. 8 is a flowchart illustrating a flow of the operation of the authenticity determination device 1 according to the first embodiment;
Fig. 9 is a diagram illustrating an example configuration of an authenticity determination device 1 according to a second embodiment;
Fig. 10 is a diagram illustrating an example configuration of a determination information registration device 3 according to the second embodiment;
Fig. 11 is a diagram illustrating an example configuration of a second determination device 58 according to the second embodiment;
Fig. 12 is a diagram illustrating an example of a pair of a second generation key ks2 and a second verification key kv2 stored in a signature key pair storage unit 57;
Fig. 13 is a flowchart illustrating a flow of the operation of the determination information registration device 3 according to the second embodiment; and
Fig. 14 is a flowchart illustrating a flow of the operation of the authenticity determination device 1 according to the second embodiment. Description of Embodiments [0009] First Embodiment
Fig. 1 is a diagram illustrating a configuration when an authenticity determination device 1 according to a first embodiment is applied to a determination target device 2.
With reference to Fig. 1, the authenticity determination device 1 is included in the determination target device 2, the authenticity of which is to be determined. The authenticity determination device 1 has an authenticity determination function for proving that the determination target device 2 is an authentic device by using a signature verification key specific to the determination target device 2. In the authenticity

determination device 1, determination information for authenticity determination is registered by a determination information registration device 3 when the determination target device 2 is manufactured at a factory. Then, the determination target device 2 including the authenticity determination device 1 in which the determination information has been registered is shipped from the factory as a product. [0010] The configuration of the authenticity determination device 1 according to the first embodiment will now be described.
Fig. 2 is a diagram illustrating an example configuration of the authenticity determination device 1 according to the first embodiment.
With reference to Fig. 2, a secure circuit 20 is a circuit having tamper resistance to prevent free access by a malicious attacker, and in particular, a circuit to prevent access to a verification key to be described later from the outside of the secure circuit 20. The secure circuit 20 can be implemented by an IC (Integrated Circuit) chip which is an integrated circuit, for example.
[0011] A key information storage unit 21 is a memory to store key information required by a verification key derivation unit 22 to derive the verification key. The key information storage unit 21 may simply store the verification key as digital data, or may store physical characteristic information or the like that can be used when the verification key derivation unit 22 performs key derivation. In addition, auxiliary information for the verification key derivation unit 22 to derive the same verification key each time may also be stored. Note that a key derivation process using the physical characteristic information or the like can be realized using existing PUF technology.
[0012] The verification key derivation unit 22 derives the verification key which is information specific to the determination target device 2 by using the key information

stored in the key information storage unit 21. The verification key derivation unit 22 may perform processing to simply read the verification key stored as digital data in the key information storage unit 21, or may derive the verification key as information specific to the determination target device 2 by using the physical characteristic information or the like stored in the key information storage unit 21. Note that when the key derivation using the verification key derivation unit 22 is executed a plurality of times, the same verification key is derived each time. When the key derivation is performed using physical characteristics, there is a possibility that the physical characteristics have errors. Thus, the verification key derivation unit 22 may be provided with means to correct errors and derive the same verification key each time. This means can be realized using error correction which is existing encoding technology.
[0013] A signature verification unit 23 performs a signature verification process using the verification key derived by the verification key derivation unit 22. This signature verification process can be realized using signature verification technology which is existing cryptographic technology.
[0014] A communication unit 24 is a communication module that communicates with a communication unit 28 outside the secure circuit 20.
[0015] A device information storage unit 25 is a memory to store device information which is information specific to the determination target device 2. Examples of the device information include text information such as a device name, a date of manufacture, and a serial number and image information such as device appearance of the determination target device 2.
[0016] A signature storage unit 26 is a memory to store signature information which is a result of performing a signature generation process for the device information stored

in the device information storage unit 25 by using a generation key paired with the
verification key derived by the verification key derivation unit 22.
[0017] A determination unit 27 determines whether the signature information stored
in the signature storage unit 26 is correct signature information for the device
information stored in the device information storage unit 25 by using the signature
verification unit 23 inside the secure circuit 20.
[0018] The communication unit 28 is a communication module that communicates
with the communication unit 24 inside the secure circuit 20 and communicates with the
outside of the determination target device 2.
[0019] Fig. 3 is a diagram illustrating an example of a hardware configuration of the
authenticity determination device 1.
The authenticity determination device 1 is a computer, and each component of the authenticity determination device 1 can be implemented by a program. As the hardware configuration of the authenticity determination device 1, a memory 31, a processor 32, a secure circuit 33, a communication module 34, an input interface 35, and a display 36 are connected to a bus 30.
[0020] The memory 31 is, for example, a main storage device such as a RAM (Random Access Memory) and an external storage device such as a ROM (Read Only Memory), a flash memory, or a hard disk device.
[0021] The processor 32 is a CPU (Central Processing Unit) or the like that executes a program.
[0022] The secure circuit 33 is an IC (Integrated Circuit) chip which is an integrated circuit, and the secure circuit 33 includes an arithmetic circuit that executes arithmetic processing of each component implemented by software, and an internal memory to store a software execution program as well as data and processing results that are

processed by the software execution program.
[0023] The communication module 34 is an electronic circuit that executes data
communication processing, and is a communication board or the like, for example.
[0024] The input interface 35 is a device that processes input data to the authenticity
determination device 1, and is a touch panel, a hardware key, a mouse, a keyboard, or
the like, for example.
[0025] The display 36 is a device that displays output data of a result of authenticity
determination by the authenticity determination device 1.
[0026] The program is normally stored in the memory 31 or the internal memory
inside the secure circuit 33, and is read and executed by the processor 32 or the
arithmetic circuit inside the secure circuit 33. This program is a program for
implementing the functions described as the verification key derivation unit 22, the
signature verification unit 23, the communication unit 24, the determination unit 27, and
the communication unit 28 that constitute the authenticity determination device 1.
[0027] Furthermore, an operating system (OS) is also stored in the external storage
device of the memory 31, and at least a part of the OS is loaded into the main storage
device. The processor 32 executes the above-described program while executing the
OS.
[0028] In the following description of the embodiment, information and data stored in
the key information storage unit 21, the device information storage unit 25, and the
signature storage unit 26, and information, data, signal values, and variable values
indicating results of processing by the verification key derivation unit 22, the signature
verification unit 23, the communication unit 24, the determination unit 27, and the
communication unit 28 are stored as files in the memory 31.
[0029] Note that the configuration of Fig. 3 is merely an example of the hardware

configuration of the device, and the hardware configuration of the device is not limited to the configuration illustrated in Fig. 3, and other configurations may be adopted. [0030] Fig. 4 is a diagram illustrating an example configuration of the determination information registration device 3 according to the first embodiment.
With reference to Fig. 4, a signature key pair generation unit 40 generates a pair of a generation key and a verification key of a signature which are required for use of a digital signature. The process for generating the pair of the generation key and the verification key can be realized using public-key cryptographic technology which is existing cryptographic technology. For example, a private key of RSA cryptography is generated as the generation key of the signature, and a public key of RSA cryptography that is paired with the private key is generated as the verification key of the signature. [0031] A signature generation unit 41 generates signature information which is a digital signature for a given input by using the generation key generated by the signature key pair generation unit 40. The process for generating the signature information can be realized using the public-key cryptographic technology which is existing cryptographic technology.
[0032] A determination information registration unit 43 registers the verification key generated by the signature key pair generation unit 40, the signature information generated by the signature generation unit 41, and the like in the determination target device 2.
[0033] A communication unit 42 communicates with the outside of the determination information registration device 3.
[0034] Fig. 5 is a diagram illustrating an example of a hardware configuration of the determination information registration device 3.
The determination information registration device 3 is a computer, and each

component of the determination information registration device 3 can be implemented
by a program. As the hardware configuration of the determination information
registration device 3, a memory 51, a processor 52, a communication module 53, an
input interface 54, and a display 55 are connected to a bus 50.
[0035] The memory 51 is, for example, a main storage device such as a RAM
(Random Access Memory) and an external storage device such as a ROM (Read Only
Memory), a flash memory, or a hard disk device.
[0036] The processor 52 is a CPU (Central Processing Unit) or the like that executes a
program.
[0037] The communication module 53 is an electronic circuit that executes data
communication processing, and is a communication board or the like, for example.
[0038] The input interface 54 is a device that processes input data to the
determination information registration device 3, and is a touch panel, a hardware key, a
mouse, a keyboard, or the like, for example.
[0039] The display 36 is a device that displays output data such as a status of a
registration process by the determination information registration device 3.
[0040] The program is normally stored in the memory 51, and is read and executed by
the processor 52. This program is a program for implementing the functions described
as the signature key pair generation unit 40, the signature generation unit 41, the
communication unit 42, and the determination information registration unit 43 that
constitute the determination information registration device 3.
[0041] Furthermore, an operating system (OS) is also stored in the external storage
device of the memory 51, and at least a part of the OS is loaded into the main storage
device. The processor 52 executes the above-described program while executing the
OS.

[0042] In the following description of the embodiment, information, data, signal values, and variable values indicating results of processing by the signature key pair generation unit 40, the signature generation unit 41, the communication unit 42, and the determination information registration unit 43 are stored as files in the memory 51. [0043] Note that the configuration of Fig. 5 is merely an example of the hardware configuration of the device, and the hardware configuration of the device is not limited to the configuration illustrated in Fig. 5, and other configurations may be adopted. [0044] A flow of the operation of the authenticity determination device 1 according to the first embodiment will now be described. The operation of the authenticity determination device 1 is roughly divided into two processes: (1) a registration process of authenticity determination information and (2) an authenticity determination process. Each process will be described below with reference to a flowchart. Note that the communication unit of each device is used for transmitting and receiving information between the devices. [0045] (1) Registration Process of Authenticity Determination Information
In the registration process of authenticity determination information, the determination information registration device 3 registers determination information in the authenticity determination device 1 included in the determination target device 2, the authenticity of which is to be determined, the determination information being information necessary for authenticity determination. In this embodiment, it is assumed that the determination target device 2 has been manufactured and device information which is information on this device has been stored in the device information storage unit 25, prior to this registration process.
Fig. 6 is a diagram illustrating an example of the device information stored in the device information storage unit 25.

In Fig. 6, the device information indicates an example in which the device name is ABC-device, the date of manufacture is January 16, 2015, and the serial number is 012345.
[0046] Fig. 7 is a flowchart illustrating a flow of the operation of the determination information registration device 3 according to the first embodiment.
First, in step SI 00, the signature key pair generation unit 40 of the determination information registration device 3 generates a pair of a signature generation key ksl and a verification key kvl of a signature which are required for use of a digital signature. In the process for generating the signature generation key ksl and the verification key kvl of the signature, the following key generation algorithm is executed, for example.
Step 1: Generate sufficiently large prime numbers p and q, and let n = pq. Step 2: Let (p be Euler's cp function and choose a positive number e that is less than cp (n) and is relatively prime to 9 (n).
Step 3: Find a positive number d that gives de = 1 (mod (p(n)). Step 4: Determine d as a generation key which is secret information, and determine e and n as a verification key which is public information. [0047] Next, in step SI01, the signature generation unit 41 acquires device information m from the device information storage unit 25 of the authenticity determination device 1 via the communication unit 42. Specifically, the signature generation unit 41 transmits an acquisition request for the device information m to the communication unit 28 of the authenticity determination device 1. The communication unit 28 acquires the device information m stored in the device information storage unit 25 via the determination unit 27, and transmits the device

information m to the communication unit 42 of the determination information
registration device 3. The communication unit 42 transmits the received device
information m to the signature generation unit 41.
[0048] Next, in step SI02, the signature generation unit 41 performs the following
signature generation operation Fs using the generation key ksl of the signature and
generates signature information si.

si = Fs(m, d) = md (mod n)
where m: device information, d: secret information, and n: public information.
Here, since d = ksl, si = Fs(m, ksl) = m sl (mod n) [0049] Note that the device information m is given by concatenation of pieces of information stored in the device information storage unit 25, for example. In the example of Fig. 6, the device information m is ABC-device20150116012345 by concatenating pieces of information, namely, ABC-device of the device name, 2015116 of the date of manufacture, and 012345 of the serial number.
[0050] Next, in step SI03, the determination information registration unit 43 registers key information for deriving the verification key kvl in the key information storage unit 21 of the determination target device 2. As the key information, for example, the verification key kvl itself may be registered, or by using the existing PUF technology or the like, physical characteristic information or the like that can be used when the verification key derivation unit 21 performs key derivation may be stored. [0051 ] Finally, in step S104, the determination information registration unit 43 registers the signature information sl in the signature storage unit 26 of the determination target device 2. Specifically, the determination information registration unit 43 transmits a registration request for the signature information sl together with the

signature information si to the communication unit 28 of the authenticity determination device 1 via the communication unit 42. The communication unit 28 stores the received signature information si in the signature storage unit 26 via the determination unit 27.
With this, the determination information registration device 3 ends the registration process of authenticity determination information. [0052] (2) Authenticity Determination Process
In the authenticity determination process, the authenticity determination device 1 in which the determination information has been registered by the registration process of authenticity determination information of (1) determines whether the determination target device 2 is an authentic device by using the verification key specific to the determination target device 2.
[0053] Fig. 8 is a flowchart illustrating a flow of the operation of the authenticity determination device 1 according to the first embodiment.
First, in step S200, the determination unit 27 reads the device information m stored in the device information storage unit 25 and the signature information si stored in the signature storage unit 26.
[0054] Next, in step S201, the determination unit 27 requests the signature verification unit 23 inside the secure circuit 20 to verify whether the signature information si is correct signature information for the device information m. Specifically, the determination unit 27 transmits a verification request for the signature information si and the device information m together with the signature information si and the device information m to the communication unit 24 inside the secure circuit 20 via the communication unit 28. The communication unit 24 transmits the received verification request together with the signature information si and the device

information m to the signature verification unit 23 to request verification. The signature verification unit 23 requests the verification key derivation unit 22 to derive the verification key kvl necessary for verification.
[0055] Next, in step S202, using the key information stored in the key information storage unit 21, the verification key derivation unit 22 inside the secure circuit 20 derives the verification key kvl which is information specific to the determination target device 2. For the verification key kvl, for example, the verification key kvl itself registered in the key information storage unit 21 may be used, or key derivation may be performed with physical characteristic information or the like registered in the key information storage unit 21 by using the existing PUF technology or the like. [0056] Next, in step S203, the signature verification unit 23 performs the following signature verification operation Fv with the verification key kvl to verify the validity of the combination of the device information m and the signature information si, and transmits a verification result rl that has been obtained to the determination unit 27.
rl = Fv(m, si, e) = "verification success" (if m = sle (mod n)) "verification failure" (if m ^ sle (mod n))
where m: device information, si: signature information, and e, n: public information (verification key kvl).
[0057] Next, in step S204, the determination unit 27 determines whether or not the verification is successful based on the verification result rl by the signature verification unit 23. If the verification result rl is "verification success", the branch of Yes leads to step S205, and that the determination target device 2 is an authentic device is output together with the device information m, for example, to the display 36. If the verification result rl is "verification failure", the branch of No leads to step S206, and

that the determination target device 2 is not an authentic device is output together with the device information m, for example, to the display 36.
With this, the authenticity determination device 1 ends the authenticity determination process.
[0058] After completion of the authenticity determination process described above, a person who makes determination decides that the determination target device 2 is authentic only if the device information m corresponds to the determination target device 2 and the obtained determination result indicates that the device is authentic. [0059] As described above, in the invention according to the first embodiment, it is possible to obtain an effect of being able to make it difficult to manufacture a counterfeit product using parts of an authentic product by performing verification using device information specific to a device and concerning the entirety of the device including an integrated circuit. The correspondence between the device information m and the signature information si is determined to be valid only when the verification key kvl is used and the verification key kvl cannot be freely accessed from the outside of the secure circuit 20. Thus, unless the secure circuit 20 is completely duplicated, a counterfeit product that exploits the valid combination (m, si) cannot pass authenticity determination, and complete duplication of the secure circuit 20 is blocked by the PUF technology or the like.
[0060] Since the output of the determination unit 27 includes the device information m, an attacker who tries to falsify only the device name or appearance based on an authentic determination target device 2 is required to tamper with the device information m. According to the present invention, this tampering can be detected by the digital signature technology. Even if the valid combination (m, si) is obtained from an expensive determination target device 2 and it is written to the device

information storage unit 25 and the signature storage unit 26 of an inexpensive determination target device 2, the verification keys are different between these devices, so that it is impossible to pass authenticity determination.
[0061] In this embodiment, the digital signature technology based on public-key cryptography is utilized to use different values as the generation key and the verification key of the signature. However, technology such as Hash-based Message Authentication Code (HMAC) may be used, for example, as digital signature technology based on common-key cryptography. In this case, the same value is used as the generation key and the verification key of the signature. [0062] In this embodiment, it is assumed that the device information on the determination target device 2 has been stored in the device information storage unit 25 prior to the registration process of authenticity determination information of (1) described above. However, the determination information registration device 3 may store the device information in the device information storage unit 25 of the determination target device 2.
[0063] In this embodiment, the person who makes determination checks the correspondence between the device information m and the determination target device 2 in the authenticity determination process of (2) described above. A function of automating this may be provided. In particular, when the device information m includes image information such as the appearance of the determination target device 2, there may be provided a function of mechanically checking the image information included in the device information m against image information obtained by photographing the determination target device 2 on the spot and automatically determining whether there is a coincidence in appearance. [0064] In this embodiment, it is assumed that the device information m and the

signature information of the determination target device 2 are electrically stored in the device information storage unit 25 and the signature storage unit 26. However, these may be printed or displayed on the housing of the determination target device 2 in the form of characters, barcodes, two-dimensional codes, or the like. In this case, these pieces of information are input to the determination unit 27 by appropriate means corresponding to each printing or display. By thus printing or displaying the device information m and the signature information on the housing of the determination target device 2, there is an effect of facilitating reading and input of the device information m and the signature information. [0065] Second Embodiment
The authenticity determination process according to the first embodiment is secure against an attacker who tampers with the device information storage unit 25 and the signature storage unit 26 of the authenticity determination device 1, but may not be secure against a powerful attacker who also tampers with the determination unit 27. In a second embodiment, there will be described an embodiment that realizes an authenticity determination device 1 which is secure also against the above-mentioned powerful attacker by using a second verification key different from a verification key derived inside the authenticity determination device 1.
[0066] The configuration of the authenticity determination device 1 according to the second embodiment will now be described.
Fig. 9 is a diagram illustrating an example configuration of the authenticity determination device 1 according to the second embodiment.
With reference to Fig. 9, a second signature storage unit 56 is a memory to store second signature information which is a result of performing a signature generation process for device information stored in a device information storage unit 25

by using a second generation key stored in a signature key pair storage unit 57 of a
determination information registration device 3. Each of the other components in Fig.
9 is substantially the same as the component of the same name in the authenticity
determination device 1 according to the first embodiment, and thus description will be
omitted.
[0067] Fig. 10 is a diagram illustrating an example configuration of the determination
information registration device 3 according to the second embodiment.
With reference to Fig. 10, the signature key pair storage unit 57 is a memory to store, as a pair, the second generation key for generating the second signature information to be stored in the second signature storage unit 56 of the authenticity determination device 1 and a second verification key for verifying the second signature information. Each of the other components in Fig. 10 is substantially the same as the component of the same name in the determination information registration device 3 of the first embodiment, and thus description will be omitted. [0068] Fig. 11 is a diagram illustrating an example configuration of a second determination device 58 according to the second embodiment.
With reference to Fig. 11, a second verification key storage unit 60 is a memory to store the second verification key for verifying the second signature information stored in the second signature storage unit 56 of the authenticity determination device 1.
[0069] A signature verification unit 61 performs a signature verification process by using the second verification key stored in the second verification key storage unit 60. This signature verification process can be realized using the signature verification technology which is existing cryptographic technology. The signature verification unit 61 is an example of a second signature verification unit.

[0070] A determination unit 62 determines, by using the signature verification unit 61,
whether the second signature information stored in the second signature storage unit 56
of the authenticity determination device 1 is correct signature information for the device
information stored in the device information storage unit 25 of the authenticity
determination device 1. The determination unit 62 is an example of a second
determination unit.
[0071] A communication unit 59 is a communication module that communicates with
the outside of the second determination device 58.
[0072] The hardware configuration of the second determination device 58 is
substantially the same as the hardware configuration illustrated in Fig. 5.
A program is normally stored in a memory 51, and is read and executed by a processor 52. This program is a program for implementing the functions described as the communication unit 59, the signature verification unit 61, and the determination unit 62 that constitute the second determination device 58.
[0073] A flow of the operation of the authenticity determination device 1 according to the second embodiment will now be described. The operation of the authenticity determination device 1 is roughly divided into four processes: (1) initial setting of the entire system, (2) a registration process of authenticity determination information, (3) a registration process of the verification key, and (4) an authenticity determination process. Each process will be described below. Note that the communication unit of each device is used for transmitting and receiving information between the devices. [0074] (1) Initial Setting of the Entire System
In the initial setting of the entire system, a signature key pair generation unit 40 of the determination information registration device 3 generates a pair of a second generation key ks2 and a second verification key kv2 of a signature which are required

for use of a digital signature, and stores the pair in the signature key pair storage unit 57.
Fig. 12 is a diagram illustrating an example of the pair of the second generation key ks2 and the second verification key kv2 stored in the signature key pair storage unit 57. [0075] (2) Registration Process of Authenticity Determination Information
The registration process of authenticity determination information is executed after the initial setting of the entire system of (1), and the determination information registration device 3 registers determination information in the authenticity determination device 1 included in the determination target device 2, the authenticity of which is to be determined, the determination information being information necessary for authenticity determination. As in the first embodiment, it is assumed that the determination target device 2 has been manufactured and device information which is information on this device has been stored in the device information storage unit 25, prior to this registration process. A storage example of the device information is substantially the same as the example illustrated in Fig. 6.
[0076] Fig. 13 is a flowchart illustrating a flow of the operation of the determination information registration device 3 according to the second embodiment.
First, all the process described in the flowchart of Fig. 7 relating to (1) the registration process of authenticity determination information according to the first embodiment is executed in substantially the same manner. Specifically, the process of step S300 through S304 in Fig. 13 is executed.
[0077] Next, in step S305, a signature generation unit 41 performs the following signature generation operation Fs with the generation key ks2 of the signature and generates signature information s2.

s2 = Fs(m,d) = md (mod n)
where m: device information, d: secret information, and n: public information.
Here, since d = ks2, s2 = Fs(m,ks2) = mks2 (mod n). [0078] Finally, in step S306, the determination information registration unit 43 registers the signature information s2 in the second signature storage unit 56 of the determination target device 2. Specifically, the determination information registration unit 43 transmits a registration request for the signature information s2 together with the signature information s2 to the communication unit 28 of the authenticity determination device 1 via the communication unit 42. The communication unit 28 stores the received signature information s2 in the second signature storage unit 56.
With this, the determination information registration device 3 ends the registration process of authenticity determination information. [0079] (3) Registration Process of the Verification Key
The registration process of the verification key is executed after the initial setting of the entire system of (1), and the determination information registration device 3 registers the determination information in the second determination device 58 that performs authenticity determination, the determination information being information necessary for authenticity determination. Specifically, the communication unit 42 of the determination information registration device 3 transmits the second verification key kv2 stored in the signature key pair storage unit 57 to the second determination device 58. Upon receiving the second verification key kv2, the second determination device 58 stores it in the second verification key storage unit 60.
With this, the determination information registration device 3 ends the registration process of authenticity determination information in the second determination device 58.

[0080] (4) Authenticity Determination Process
In the authenticity determination process, the second determination device 58 in which the second verification key has been registered by the registration process of the verification key of (3) determines whether the determination target device 2 in which the authenticity determination device 1 is included is an authentic device by using a first verification key derived by the authenticity determination device 1 and the second verification key stored in the second determination device 58. [0081] Fig. 14 is a flowchart illustrating a flow of the operation of the authenticity determination device 1 according to the second embodiment.
First, in the process of steps S400 through S404, determination using the first verification key derived by the authenticity determination device 1 is performed. This process is substantially the same as the authenticity determination process of (2) according to the first embodiment, and thus description will be omitted. [0082] Next, in step S404, a determination unit 27 determines whether or not the verification is successful based on a verification result rl by the signature verification unit 23. If the verification result rl is "verification failure", the branch of No leads to step S405, and that the determination target device 2 is not an authentic device is output together with the device information m, for example, to the display 36 and the process is ended. If the verification result rl is "verification success", the branch of Yes leads to step S406.
[0083] Next, in step S406, the signature verification unit 61 of the second determination device 58 reads the device information m and the signature information s2 from the authenticity determination device 1. Specifically, the signature verification unit 61 transmits an acquisition request for the device information m and the signature information s2 to the communication unit 28 of the authenticity

determination device 1 via the communication unit 59. The communication unit 28 of the authenticity determination device 1 acquires the device information m stored in the device information storage unit 25 via the determination unit 27, also acquires the signature information s2 stored in the second signature storage unit 56, and transmits them to the communication unit 59 of the second determination device 58. The communication unit 59 of the second determination device 58 transmits the received device information m and signature information s2 to the signature verification unit 61. [0084] Next, in step S407, the signature verification unit 61 performs the following signature verification operation Fv with the verification key kv2 to verify the validity of the combination of the device information m and the signature information s2, and transmits a verification result r2 that has been obtained to the determination unit 62.
r2 = Fv(m, s2, e) = "verification success" (if m = s2e (mod n)) "verification failure" (if m ^ s2e (mod n))
where m: device information, s2: signature information, and e, n: public information (verification key kv2).
[0085] Next, in step S408, the determination unit 62 determines whether or not the verification is successful based on the verification result r2 by the signature verification unit 61. If the verification result r2 is "verification success", the branch of Yes leads to step S409, and that the determination target device 2 is an authentic device is output together with the device information m, for example, to the display 55. If the verification result r2 is "verification failure", the branch of No leads to step S405, and that the determination target device 2 is not an authentic device is output together with the device information m, for example, to the display 55.
With this, the authenticity determination device 1 ends the authenticity

determination process.
[0086] As described above, in the invention according to the second embodiment, the
correspondence between the device information m and the signature information s2 is
checked using the second verification key kv2 that exists outside the determination
target device 2. Thus, in addition to the effect described in the first embodiment, there
is an effect of being able to correctly detect a counterfeit product even if there exists a
powerful attacker who tampers with the determination unit 27 of the authenticity
determination device 1. The implementation variations described in the first
embodiment can also be similarly applied to the second embodiment.
[0087] The second embodiment is an embodiment in which when a plurality of
determination target devices exist, the determination information registration device 2
uses the second generation key and the second verification key that are common to all
the determination target devices. However, a different second generation key and a
different second verification key may be generated for each determination target device.
In this case, however, the second verification key storage unit 60 of the second
determination device 58 stores each of a plurality of second verification keys in
association with a corresponding one of the determination target devices.
[0088] In the second embodiment, the same digital signature algorithm is used for the
signature information si and the signature information s2, but different digital signature
algorithms may be used.
[0089] In the second embodiment, the determination information registration device 3
and the second determination device 58 are separate devices, but one device may
implement the both functions.
[0090] In the second embodiment, no particular reference is made to communication
means between the devices. However, in the authenticity determination process of (4),

communication between the authenticity determination device 1 and the second determination device 58 may be performed via the Internet, for example. That is, the second determination device 58 may be placed, for example, on a Web server and the authenticity determination device 1 may request the second determination device 58 to perform authenticity determination via the Internet.
[0091] In the second embodiment, the second determination device 58 stores only the second verification key, but it may store additional information on the determination target device 2. For example, when the device information held by the authenticity determination device 1 is only text information such as a device name, the second determination device 58 may store correspondence information such as a device name and an appearance image, and the determination unit 62 may also output a corresponding appearance image and the like when outputting the device information. [0092] In the second embodiment, in the authenticity determination process of (4), the process ends when the verification result rl is "verification failure" and it is determined that the device is not authentic, but the process may continue to perform determination using the second verification key and all determination results may be output in detail. Reference Signs List
[0093] 1: authenticity determination device; 2: determination target device; 3: determination information registration device; 20, 33: secure circuit; 21: key information storage unit; 22: verification key derivation unit; 23, 61: signature verification unit; 24, 28, 42, 59: communication unit; 25: device information storage unit; 26: signature storage unit; 27, 62: determination unit; 30, 50: bus; 31,51: memory; 32, 52: processor; 34, 53: communication module; 35, 54: input interface; 36, 55: display; 40: signature key pair generation unit; 41: signature generation unit; 43: determination information registration unit; 56: second signature storage unit; 57:

signature key pair storage unit; 58: second determination device; 60: second verification key storage unit

[Claim 1] An authenticity determination device comprising:
a device information storage unit to store device information indicating information specific to a determination target device, authenticity of which is to be determined;
a signature storage unit to store a signature for the device information;
a key information storage unit to store key information being information for deriving a verification key corresponding to a generation key with which the signature has been generated;
a verification key derivation unit to derive the verification key by using the key information;
a signature verification unit to verify validity of a combination of the device information and the signature by using the verification key derived by the verification key derivation unit; and
a determination unit to determine the authenticity of the determination target device, based on the validity verified by the signature verification unit.
[Claim 2] The authenticity determination device according to claim 1,
wherein the key information storage unit, the verification key derivation unit, and the signature verification unit are contained in a secure circuit having tamper resistance.
[Claim 3] The authenticity determination device according to claim 2,
wherein the key information storage unit stores the key information which is

specific to the secure circuit and which is generated by PUF (Physical Unclonable Function) by using a physical characteristic of the secure circuit, and
wherein the verification key derivation unit derives the verification key by using the key information generated by the PUF.
[Claim 4] The authenticity determination device according to claim 1, further comprising:
a determination information registration device including
a signature key pair generation unit to generate a pair of the generation key and the verification key of the signature;
a signature generation unit to generate the signature by using the device information and the generation key which is generated by the signature key pair generation unit; and
a determination information registration unit to register, in the key information storage unit, the key information being information for deriving the verification key generated by the signature key pair generation unit, and register the signature generated by the signature generation unit in the signature storage unit.
[Claim 5] The authenticity determination device according to claim 1, further comprising:
a second signature storage unit to store a second signature for the device information, the second signature being different from the signature; and
a second determination device including
a second verification key storage unit to store a second verification key different from the verification key;

a second signature verification unit to verify validity of a combination of the device information and the second signature by using the second verification key; and
a second determination unit to determine the authenticity of the determination target device, based on the validity verified by the second signature verification unit.
[Claim 6] The authenticity determination device according to claim 5, wherein in the determination information registration device, the signature key pair generation unit generates a pair of a second generation
key and a second verification key different from the generation key and the verification
key,
the signature generation unit generates a second signature by using the device
information and the second generation key which is generated by the signature key pair
generation unit, and
the determination information registration unit registers the second verification
key generated by the signature key pair generation unit in the second verification key
storage unit of the second determination device, and registers the second signature
generated by the signature generation unit in the second signature storage unit of the
authenticity determination device.
[Claim 7] The authenticity determination device according to claim 1,
wherein the device information and the signature are displayed on a housing of the determination target device.
[Claim 8] An authenticity determination method for an authenticity determination device that stores device information indicating information specific to a determination

target device, authenticity of which is to be determined, a signature for the device information, and key information being information for deriving a verification key corresponding to a generation key with which the signature has been generated, and determines the authenticity of the determination target device, the authenticity determination method comprising:
a verification key derivation step, by a verification key derivation unit, of deriving the verification key by using the key information;
a signature verification step, by a signature verification unit, of verifying validity of a combination of the device information and the signature by using the verification key derived by the verification key derivation step; and
a determination step, by a determination unit, of determining the authenticity of the determination target device, based on the validity verified by the signature verification step.