JP2014229968A - Terminal authentication system and terminal authentication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a terminal authentication system capable of using implementation means over a wide range as device physical information generation means and suppressing a frequency of implementation of a registration phase.SOLUTION: A terminal 160 includes: device physical information generation means 480 for generating physical information relating to components of the terminal 160 as device physical information; public key encryption means 411 for encrypting the device physical information and transmitting it to a server 150; terminal-side key generation means 433 for generating terminal-side random information using the device physical information; and terminal-side key verification means 473. The server 150 includes: public key decryption means 410 for decrypting the encrypted device physical information; physical information storage means 450 for storing the device physical information; server-side key generation means 432 for generating server-side random information using the device physical information; collation means 460 for collating the terminal 160; and server-side key verification means 472.

Description

  The present invention relates to a terminal authentication system and a terminal authentication method using specific information of a terminal device.

  In order to realize safe information and a communication system, authentication processing for determining whether or not a communication partner is a regular partner is necessary in communication between a server and a terminal. The authentication process is premised on the presence of device-specific information (ID: identification). The serial number assigned to the terminal is a representative ID, but it is easy for an attacker who has obtained a legitimate terminal to obtain the serial number. In many cases, the serial number of another terminal can be estimated from the serial number of a certain terminal.

  If a terminal has a random secret key, it is difficult to guess the secret key of another terminal even if the secret key of the terminal leaks, but it is necessary to securely hold the secret key. In the method of keeping the secret key in the non-volatile memory, the attacker who obtained the terminal may be able to read the secret key easily, and if the memory is copied as it is without analyzing the contents of the memory A duplicate may be created. A technique for dealing with such an attack is called a tamper resistant technique, and as a general technique, for example, a method having a secret key in a volatile memory is known. However, this method has a problem that the cost becomes high because a battery of a memory for holding a secret key, a sensor for detecting tampering, and the like are required.

  2. Description of the Related Art In recent years, in devices that constitute equipment, research has been progressing on techniques for generating unique information of individual devices using physical variations inevitably generated in the manufacturing process and using the unique information for authentication. In this technique, a function called Physically Uncapable Function (PUF) is generally used.

  FIG. 14 is a block diagram illustrating a configuration of a general authentication system using a PUF. Authentication is performed between the terminal 110 and the server 100. The terminal 110 includes device physical information generation means 120. The device physical information generation unit 120 uses a device that originally exists as a component of the terminal for the PUF. The device physical information generation unit 120 outputs a physical quantity corresponding to the component specified by the input. For example, the device physical information generation unit 120 based on the StaticRAM uses each bit of the RAM as a PUF element. In that case, the user specifies the bit to be used. Then, the device physical information generation unit 120 outputs an initial value of the bit when the power is turned on, for example.

  The following Patent Documents 1 and 2 and Non-Patent Document 1 disclose PUFs that use variations among wiring delays inevitably generated in the manufacturing process as used by the device physical information generation unit 120.

  A typical method of using the PUF is challenge-response authentication, and authentication of a terminal is performed in two stages of a registration phase and an authentication phase. It is assumed that the registration phase is performed before the start of use of the terminal and is performed in a safe environment without eavesdropping or spoofing.

  Hereinafter, the operation of a general authentication system using challenge-response authentication will be described. FIG. 15 is a flowchart showing an operation in a registration phase of a general authentication system using challenge-response authentication. FIG. 16 is a flowchart showing an operation in an authentication phase of a general authentication system using challenge-response authentication.

[Registration phase]
In response to a registration request from the terminal 110, the server 100 sends a plurality of data (challenges) specifying elements in the device physical information generation unit 120 (step 1a). The terminal 110 sends a response of the device physical information generation unit 120 to the challenge in step 1a to the server 100 (step 2a). The server 100 holds the pair of challenge and response (step 3a).

[Authentication Phase]
In response to the authentication request from the terminal 110, the server 100 sends a part of the held challenge (step 1b). The terminal 110 sends a response of the device physical information generation means 120 to the challenge in step 1b to the server 100 (step 2b). The server 100 compares this response with the response held in step 3a (step 3b). The server 100 performs an authentication process using the comparison result of step 3b (step 4b). Specifically, when it is determined that the comparison result in step 3b is sufficiently close, the server 100 authenticates that the response transmission source terminal is the legitimate terminal 110. If the server 100 determines that there is a predetermined difference in the comparison result in step 3b, the server 100 determines that the terminal that sent the response is not the legitimate terminal 110.

  Next, a specific example of challenge-response authentication processing will be described. FIG. 17 is an explanatory diagram showing an example of processing in the registration phase of challenge-response authentication. FIG. 18 is an explanatory diagram illustrating an example of processing in an authentication phase of challenge-response authentication. In the registration phase, the server 100 generates a table (challenge-response table) including a pair (c, f (c)) of the challenge c and the response f (c) from the terminal 110. In the authentication phase, the server 100 performs an authentication process by comparing the response f ′ (c) from the terminal to the challenge c in this table with f (c) generated in the registration phase. Since physical information is fluctuated by environmental factors such as fluctuations due to temperature and thermal noise, it becomes a problem to collate in consideration of fluctuations caused by these environmental factors.

  As a general technique for solving this problem, it is conceivable to configure the device physical information generation unit 120 so that an output that reduces the influence of environmental factors can be obtained. For example, a method of outputting a relative comparison result between physical information instead of physical information itself is conceivable. As a technique proposed for this purpose, Non-Patent Document 1 discloses a method using an arbiter PUF.

  FIG. 19 is a block diagram illustrating a configuration example of an arbiter PUF used in challenge-response authentication. The device physical information generation unit 120 using the arbiter PUF is configured by a path in which wirings having the same length are connected in multiple stages by the selector 300. For the selectors paired at each stage, the challenge forms two paths that can be regarded as the same length by selecting the same type of path. After determining this path, the device physical information generation unit 120 transmits a signal, and the last arbiter (D-FF circuit) 310 determines which path the signal has reached faster. By design, even if the path length is the same, both delays differ for each device, and this prediction is difficult. Therefore, the determination result can be used as unique information that is difficult to guess. Although the delay of the circuit varies depending on the temperature, the arbiter PUF compares only the magnitudes of the delays of two paths having the same path length, so that the relative relationship is maintained to some extent, so that a relatively stable output can be obtained. .

In order to ensure security in the challenge-response authentication, it is necessary to restrict the use of the challenge once used in the authentication phase to avoid a replay attack in which the attacker sends it again. The device physical information generation means 120 needs to be able to cope with a sufficiently large number of challenges. When the Arbiter PUF is composed of n stages of selectors, 2 ⁿ paths can be constructed, and this is the total number of challenges. If n = 64 becomes 2 number ⁶⁴ challenge, the challenge of a sufficient number of times - thereby enabling corresponding response authentication.

  Similar to Arbiter PUF, Patent Document 2 and Non-Patent Document 1 show a method using a ring oscillator circuit as a circuit for comparing the magnitudes of delays of the same circuit.

Special table 2007-509563 Special table 2009-524998

G. E. Shu and S. Devadas, “Physically Unclonable Functions for Device Generation and Secret Key Generation,” Proc. 44th Design Automation Conference, pp.9-14.

  The PUF used in the challenge-response authentication method using the device physical information generation means 120 is limited to a sufficiently large number of challenges, such as an arbiter PUF. For example, a PUF using a ring oscillator circuit described in Patent Document 2 or Non-Patent Document 1 has a challenge number that is about the square of the number of circuits, and is not suitable for challenge-response authentication as it is. It is necessary to generate the same response with high reliability from the device physical information. For this reason, the device physical information generating means is limited to means capable of achieving very high reproducibility using, for example, an error correction code.

  Furthermore, in the arbiter PUF, when the temperatures of the registration phase and the authentication phase are greatly different, the reproducibility tends to deteriorate greatly. At this time, a large number of challenge-response pairs are required for authentication. For this reason, it is necessary to generate a large number of challenge-response pairs in the registration phase or to execute the registration phase at a high frequency.

  An object of the present invention is to provide a terminal authentication system and a terminal authentication method that can use a wide range of means as device physical information generation means and can suppress the frequency of execution of the registration phase.

  A terminal authentication system according to the present invention includes a terminal and a server, performs a registration process for the terminal in a registration phase, and performs an authentication process for the terminal in an authentication phase. Device physical information generating means for generating physical information related to a component as device physical information, public key encryption means for encrypting the device physical information using a server public key and transmitting the encrypted information to the server, and using the device physical information Terminal-side key generation means for generating terminal-side random information and terminal-side key verification means for acquiring the terminal-side random information, wherein the server uses the server secret key to encrypt the device physical Public key encryption / decryption means for decrypting information, physical information storage means for storing the decrypted device physical information, and decryption Server-side key generation means for generating server-side random information using the converted device physical information, the device physical information decrypted by the public key encryption / decryption means in the registration phase, and the disclosure in the authentication phase The server side key verification includes: verification means for verifying the terminal by comparing the device physical information decrypted by the key encryption / decryption means; and server side key verification means for acquiring the server side random information. And the terminal-side key verification means verify the authentication process by checking whether the terminal-side random information and the server-side random information match.

  A terminal authentication method according to the present invention is a terminal authentication method in which a terminal and a server are used to perform registration processing of the terminal in a registration phase and perform authentication processing of the terminal in an authentication phase. Generates physical information on the components of the terminal as device physical information, encrypts the device physical information using a server public key, and transmits the encrypted information to the server. The server encrypts using the server secret key. The decrypted device physical information is stored, and the decrypted device physical information is stored, and in the authentication phase, the terminal generates physical information related to the components of the terminal as device physical information, and generates a server public key. Using the device physical information to encrypt the device physical information and sending it to the server. Generating information, the server decrypts the encrypted device physical information using a server secret key, generates server-side random information using the decrypted device physical information, and the registration phase The terminal physical verification is performed by comparing the device physical information decrypted in step 1 and the device physical information decrypted in the authentication phase, and at least one of the terminal and the server is a random The authentication process is verified by confirming whether the information matches the server-side random information.

  The present invention can use a wide range of realization means as device physical information generation means, and can suppress the frequency of execution of the registration phase.

It is a block diagram which shows the structure of 1st Embodiment of the terminal authentication system by this invention. It is a flowchart which shows the operation | movement in the registration phase of 1st Embodiment of the terminal authentication system by this invention. It is a flowchart which shows the operation | movement in the authentication phase of 1st Embodiment of the terminal authentication system by this invention. It is a block diagram which shows the structure of 2nd Embodiment of the terminal authentication system by this invention. It is a flowchart which shows the operation | movement in the registration phase of 2nd Embodiment of the terminal authentication system by this invention. It is a flowchart which shows the operation | movement in the authentication phase of 2nd Embodiment of the terminal authentication system by this invention. It is a block diagram which shows the structure of the device physical information generation means using the ring oscillator circuit in an Example. It is a flowchart which shows the operation | movement in the registration phase of the device physical information generation means using the ring oscillator circuit in an Example. It is a flowchart which shows the operation | movement in the authentication phase of the device physical information generation means using the ring oscillator circuit in an Example. It is explanatory drawing which shows the result of having calculated | required by experiment the standard deviation of the frequency ratio of the ring oscillator circuit in an Example. It is explanatory drawing showing the frequency of the standard deviation shown in FIG. It is a flowchart which shows the Example of a key verification means. It is a block diagram which shows the structure of the principal part of the terminal authentication system by this invention. It is a block diagram which shows the structure of the general authentication system using PUF. It is a flowchart which shows the operation | movement in the registration phase of the general authentication system using challenge-response authentication. It is a flowchart which shows the operation | movement in the authentication phase of the general authentication system using challenge-response authentication. It is explanatory drawing which shows the example of the process of the registration phase of challenge-response authentication. It is explanatory drawing which shows the example of the process of the authentication phase of challenge-response authentication. It is a block diagram which shows the structural example of arbiter PUF used by challenge-response authentication.

Embodiment 1. FIG.
FIG. 1 is a block diagram showing the configuration of the terminal authentication system of this embodiment. The terminal authentication system of this embodiment includes a server 150 and a terminal 160. The server 150 includes a public key encryption / decryption unit 410, a server secret key 420, a key generation unit 430, a key storage unit 440, a physical information storage unit 450, a verification unit 460, and a key verification unit 470. The terminal 160 includes a public key encryption unit 411, a server public key 421, a key generation unit 431, a key storage unit 441, a key verification unit 471, and a device physical information generation unit 480. Each unit included in the server 150 and the terminal 160 is realized by, for example, hardware designed to perform specific arithmetic processing or the like, or an information processing device such as a CPU (Central Processing Unit) that operates according to a program.

  FIG. 2 is a flowchart showing the operation in the registration phase of the terminal authentication system of this embodiment. FIG. 3 is a flowchart showing the operation in the authentication phase of the terminal authentication system of this embodiment. The terminal authentication system of the present embodiment realizes authentication of the terminal 160 in two stages, a registration phase and an authentication phase. The registration phase is performed in advance before using the terminal 160. Hereinafter, each operation of the registration phase and the authentication phase of the terminal authentication system will be described.

[Registration phase]
The terminal 160 makes a registration request to the server 150, and the device physical information generation unit 480 generates device physical information (step 1c). Specifically, the device physical information generation unit 480 generates physical information regarding the components of the terminal as device physical information. The public key encryption means 411 of the terminal 160 encrypts the device physical information generated in step 1c using the server public key 421, and transmits the data obtained by the encryption to the server 150 (step 2c). The public key encryption / decryption means 410 of the server 150 decrypts the data encrypted in step 2c using the server secret key 420 and stores it in the physical information storage means 450 (step 3c).

  Note that the terminal authentication system of the present embodiment can apply any existing general method such as RSA encryption, El Gamal encryption, or elliptical encryption as a public key encryption method. In addition, although a random number may be required in the public key encryption method, the terminal authentication system of the present embodiment can also use a random number component in the device physical information.

[Authentication Phase]
The terminal 160 makes an authentication request to the server 150, and the device physical information generation unit 480 generates device physical information (step 1d). The public key encryption unit 411 of the terminal 160 encrypts the device physical information generated in step 1d using the server public key 421, and transmits the encrypted data to the server 150. Also, the key generation unit 431 generates random information using the device physical information and stores it in the key storage unit 441 (step 2d). The key generation means 431 extracts, for example, random number information as random information.

  The public key encryption / decryption means 410 of the server 150 decrypts the data obtained in step 2d using the server secret key 420 (step 3d). The collating unit 460 compares the combined data with the data stored in the physical information storage unit 450 in the registration phase, so that the terminal that transmitted the data in step 2d is the same as the registered terminal. It is determined whether or not there is (step 4d).

  The key generation unit 430 extracts, for example, random number information as random information. If the collation unit 460 determines in step 4d that the terminal that transmitted the data in step 2d is not the same as the registered terminal, the server 150 determines that the authentication has failed and ends the process. If the collating unit 460 determines in step 4d that the terminal that transmitted the data in step 2d and the registered terminal are the same, the key generating unit 430 uses the decrypted data obtained in step 3d. Random information is generated and stored in the key storage means 440 (step 5d).

  The key verification unit 470 and the key verification unit 471 perform a key verification process, and if it is confirmed that the same random information is shared, it is determined that the authentication is successful, and otherwise, it is determined that the authentication is failed (step 6d). Specifically, the key verification unit 470 acquires the random information stored in the key storage unit 441 from the terminal 160 and confirms whether it matches the random information stored in the key storage unit 440. Further, the key verification unit 471 acquires the random information stored in the key storage unit 440 from the server 170 and confirms whether it matches the random information stored in the key storage unit 441.

  In the verification process, the verification unit 460 calculates the relative statistical value of the device physical information in the registration phase and the device physical information in the authentication phase in consideration of the difference in environmental factors such as temperature, and based on the statistical value, Perform verification. In the case of device physical information by the same device, this statistical value can be expected to show a higher degree of matching than that between different devices. Therefore, whether the terminal used in the registration phase and the terminal used in the authentication phase are the same when the user sets an appropriate threshold in advance and the matching unit 460 compares the threshold and the statistical value. Can be determined.

  The key generation means 430 and 431 typically generate random information by applying a hash function such as SHA. Depending on the nature of the device physical information, a simple method such as selecting a specific bit may be applied. In this embodiment, the information output by the key generation means 430 and 431 is different for each authentication phase, and can be used as a temporary key for encryption or authentication during data communication after terminal authentication processing.

  Further, the key verification means 470 and 471 may perform the verification process by using a hash function or a block cipher with the random component generated by the key generation means 430 and 431 as a secret key.

  In the terminal authentication system of this embodiment, unlike general challenge-response authentication, an attacker cannot obtain device physical information itself because it is encrypted with a public key even if it acquires data on the communication path. . This can be detected by the verification processing in the key verification means 470 and 471 even for a retransmission attack that aims to capture transmission data from the terminal and send it later to impersonate the terminal. For this reason, if the device physical information has a sufficient amount of information, the terminal authentication system of the present embodiment is excellent in operability because secure authentication can be realized for a long time by performing a single registration phase.

  The terminal authentication system according to the present embodiment further uses a flexible verification method that takes into account fluctuations in environmental factors such as temperature because the server 150 can perform verification using device physical information in the registration phase and authentication phase as they are. it can. Due to these properties, the device physical information generation unit 480 is not limited to a unit that can obtain high reproducibility, and various realization units can be used.

Embodiment 2. FIG.
The terminal authentication system according to the first embodiment uses the output of all elements constituting the device physical information generation unit 480. In the present embodiment, a terminal authentication system using a method for transmitting a challenge from a server to specify the components of the device physical information generation unit 480 as in the general challenge-response authentication method described above will be described.

  FIG. 4 is a block diagram showing the configuration of the terminal authentication system of this embodiment. The terminal authentication system of this embodiment includes a server 170 and a terminal 180. Server 170 includes a challenge generation and storage means 500. Since the configuration of the server 170 other than the challenge generation and storage unit 500 is the same as that of the server 150 of the first embodiment, a description thereof will be omitted. Further, the configuration of the terminal 180 is the same as that of the terminal 160 of the first embodiment, and a description thereof will be omitted.

  In response to a registration request from the terminal 180, the challenge generation and storage unit 500 of the server 170 generates a challenge that specifies the components of the terminal 180 that the device physical information generation unit 480 uses to generate the device physical information. Are stored and transmitted to the terminal 180.

  FIG. 5 is a flowchart showing the operation in the registration phase of the terminal authentication system of this embodiment. FIG. 6 is a flowchart showing the operation in the authentication phase of the terminal authentication system of this embodiment. The flowcharts shown in FIGS. 5 and 6 are the same as those in the first embodiment shown in FIGS. 2 and 3 except for Steps 1c ′ and 1d ′, and thus the description thereof is omitted.

  In response to a registration request from the terminal 180, the challenge generation and storage unit 500 of the server 170 generates a challenge that specifies the components of the terminal 180 that the device physical information generation unit 480 uses to generate the device physical information. Are stored and transmitted to the terminal 180. The device physical information generation unit 480 of the terminal 180 receives the challenge, and generates device physical information as a response using an element corresponding to the challenge (step 1c ').

  The device physical information generation unit 480 of the terminal 180 receives the challenge, and generates device physical information as a response using an element corresponding to the challenge (step 1d ').

  Thus, in the terminal authentication system of the present embodiment, the device physical information used for authentication is designated as a challenge by the server, so that the device physical information used for authentication can be updated. As a result, the terminal authentication system of the present embodiment can use other elements when there is a possibility of leakage of specific information or elements that are greatly inferior in reproducibility.

  In the terminal authentication system of this embodiment, when it is confirmed that the key verification means 470 and 471 share the same random number data between the server and the terminal, the communication data is encrypted using the random number data as a secret key. And message authentication.

(Example)
Hereinafter, an example in which a ring oscillator circuit is used for the device physical information generation unit 480 of the terminal authentication system of the second exemplary embodiment will be described. In addition, the Example shown below can also be applied to the terminal authentication system of 1st Embodiment.

  FIG. 7 is a block diagram illustrating a configuration of the device physical information generation unit 480 using the ring oscillator circuit in the embodiment. Ring oscillator circuit 600 includes an odd number of inverters 600a. The number of inverters 600a depends on the required authentication accuracy and information amount, but is typically 100 or more. The selector 610 selects the output value of the ring oscillator circuit 600 according to the input challenge. The counter 620 measures the number of 0 and 1 inversions (frequency) of the output value in a certain time. The memory 630 holds the frequency of the ring oscillator circuit 600 measured by the counter 620.

  Hereinafter, operation examples of the registration phase and the authentication phase in the present embodiment will be described. FIG. 8 is a flowchart showing the operation in the registration phase of the device physical information generating means using the ring oscillator circuit in the embodiment. FIG. 9 is a flowchart showing the operation in the authentication phase of the device physical information generating means using the ring oscillator circuit in the embodiment. In the following example, it is assumed that the device physical information generation unit 480 includes 128 ring oscillator circuits 600, the output value of the counter 620 is 24 bits, and the public key encryption is 2048 bits RSA encryption.

[Registration phase]
The terminal 180 makes a registration request to the server 170, and the device physical information generation unit 480 sequentially calculates the frequencies of the 128 ring oscillator circuits 600 and stores them in the memory 630 (step 1e). The calculated frequency is 128 × 24 = 3072 bit data. The public key encryption unit 411 performs RSA encryption on this data in two steps of 1536 bits, and sends the two encrypted ciphertexts to the server 170 (step 2e). The reason why encryption is performed twice in step 2e is that the data exceeds the input size of RSA (2048 bits). The public key encryption / decryption means 410 decrypts the two ciphertexts sent in step 2e, and stores the decrypted frequencies of the 128 ring oscillator circuits 600 in the physical information storage means 450 (step 3e).

[Authentication Phase]
The terminal 180 makes an authentication request to the server 170, and the device physical information generation unit 480 sequentially calculates the frequencies of the 128 ring oscillator circuits 600 and stores them in the memory 630 (step 1f). The public key encryption unit 411 performs RSA encryption by dividing the 3072-bit frequency data twice in the same manner as in the registration phase, and transmits it to the server 170. Further, the key generation means 431 takes out the least significant 2 bits of the 128 pieces of frequency data, and stores 128 × 2 = 256 bits in the key storage means 441 (step 2f).

  The public key encryption / decryption means 410 decrypts the two ciphertexts in step 2d to restore 128 ring oscillator circuits 600 (step 3f). The collation unit 460 compares the restored data with the data stored in the physical information storage unit 450 in the registration phase, thereby determining whether the terminal that transmitted the data in step 2f and the registered terminal are the same device. Determine (step 4f). If the server 170 determines that they are not the same device, the server 170 ends as an authentication failure. When the server 170 determines that the devices are the same in step 4f, the key generation unit 430 extracts the least significant 2 bits of the 128 frequency data and stores 128 × 2 = 256 bits in the key storage unit 440 ( Step 5f).

  The server 170 and the terminal 180 determine that the authentication is successful when the key verification process is performed and it is confirmed that the same random number component is shared, and otherwise the authentication failure is determined (step 6f). . The key verification process will be described later.

  When the physical information is the frequency of the ring oscillator circuit 600, a random component accompanying thermal noise is superimposed on the frequency value. Therefore, the key generation means 430 and 431 can realize generation of random information by extracting the bits in the vicinity of the lowest order as described above.

  The specific example of the collation process of the collation means 460 in step 4f in a present Example is shown. The frequencies of the ring oscillator circuit 600 in the registration phase are set to s_1, s_2,. . . , S_128, the frequencies of the ring oscillator circuit 600 in the authentication phase are t_1, t_2,. . . , T_128. If the temperature in the registration phase and the authentication phase is different, the frequency is different, but changes in each circuit in the same way. Therefore, if the same device, the frequency ratio t_i / s_i can be expected to have a distribution concentrated around the average value. Therefore, when the following formulas (1) and (2) are calculated (sqrt () is a positive square root), the standard deviation d represented by formula (2) is compared with the case between different devices in the case of the same device. Can be expected to be sufficiently small.

m = (t_1 / s_1 +... + t_128 / s_128) / 128. ... (1)
d = sqrt (((t_1 / s_1-m) ² +... + (t_128 / s_128-m) ² ) / 128). ... (2)

  FIG. 10 is an explanatory diagram illustrating a result of an experiment for obtaining the standard deviation of the 600 frequency ratio of the ring oscillator circuit in the example. The results shown in FIG. 10 are the results of experiments conducted by creating 128 identical ring oscillator circuits 600 for each FPGA using 10 FPGAs (Field-Programmable Gate Array). In this experiment, the ring oscillator circuit 600 includes 15 inverters 600a. Further, the counter 620 counted the number of inversions of 0 and 1 of the output at 5.24 msec. The count value at this time is about 900,000 and can be represented by 20 bits.

  The diagonal components in the table shown in FIG. 10 are standard deviations of Equation (2) when the device temperature is −5 ° C. in the registration phase and the device temperature in the authentication phase is 65 ° C. with the same FPGA. The other components in the table shown in FIG. 10 indicate standard deviations calculated from Expression (2) when the authentication phase is executed with the FPGA corresponding to the column using the FPGA corresponding to the row as the registration phase.

  FIG. 11 is an explanatory diagram showing the frequency of the standard deviation shown in FIG. From this graph, in the case of using the FPGA and ring oscillator circuit 600 used in this experiment, the collating means 460 determines that the same FPGA, that is, if the standard deviation value calculated from the equation (2) is 0.003 or less, that is, It can be determined that they are the same device.

  Next, a specific example based on CBC-MAC (Cipher Block Chaining Message Authentication Code) based on the block cipher of the key verification means 470 and 471 in Step 6f will be shown. FIG. 12 is a flowchart showing an embodiment of the key verification means. In this embodiment, the value stored in the key storage unit 440 of the server 170 is K1, and the value stored in the key storage unit 441 of the terminal 180 is K2. The server 170 and the terminal 180 determine the verification data D1 and D2 in advance. D1 and D2 generally include the IDs of the server 170 and the terminal 180, and D1 and D2 are set to different values by changing the order of the IDs or using different constants.

[Key verification]
The server 170 generates a random number R1 and sends the random number R1 to the terminal 180 (step 1g). The terminal 180 encrypts data obtained by concatenating R1 and D1 in the CBC mode using K2 as a secret key, and sends the output of the final block to the server 170 (step 2g). The server 170 encrypts data obtained by concatenating R1 and D1 in the CBC mode using K1 as a secret key, and compares the final block with the data received in step 2g (step 3g). As a result of the comparison, if they match, it is determined that the data transmission source terminal matches the terminal 180 in the registration phase, and the process proceeds to 5g.

  The server 170 performs encryption in the CBC mode with respect to D2 using K1 as a secret key, and transmits the output of the final block to the terminal 180 (step 5g). The terminal 180 encrypts D2 in the CBC mode using K2 as a secret key, and compares the output of the final block with the data received in step 4g. If they match, it is determined that the terminal is correct, and if they do not match, the process ends as an authentication failure (step 6g).

  The terminal authentication system of the present embodiment can detect a retransmission attack due to terminal impersonation by the processing in steps 1g and 2g. It is possible to achieve high security against man-in-the-middle attacks by performing the above key verification process using a part of K1 and K2 and performing subsequent encrypted communication using the remaining bits as secret keys. It becomes. For example, if a block cipher with a 128-bit secret key is used, the 256-bit random number data of the key storage means in the above setting is used for the key verification process, and the remaining 128 bits are used in the subsequent data communication. It can be applied to encryption and message authentication.

  As described above, the terminal authentication system according to the present embodiment can eliminate threats caused by man-in-the-middle attacks by performing data encryption and authentication communication using random secret information that is different for each authentication phase. . In addition, the terminal authentication system according to the present embodiment can estimate random information shared in the authentication phase between the server 170 and the authorized terminal 180 even if the attacker has obtained device physical information at a certain point in time. Since it is difficult, confidentiality can be maintained.

  FIG. 13 is a block diagram showing the configuration of the main part of the terminal authentication system according to the present invention. As shown in FIG. 13, the terminal authentication system includes a terminal 160 and a server 150 as main components, performs a registration process for the terminal 160 in the registration phase, and performs an authentication process for the terminal 160 in the authentication phase. The terminal 160 includes a device physical information generation unit 480 that generates physical information related to components of the terminal 160 as device physical information, and a public key that encrypts the device physical information using the server public key and transmits the encrypted device physical information to the server 150. The server 150 includes the encryption unit 411, the terminal side key generation unit 433 that generates the terminal side random information using the device physical information, and the terminal side key verification unit 473 that acquires the terminal side random information. Public key encryption / decryption means 410 for decrypting encrypted device physical information using a key; Physical information storage means 450 for storing the decrypted device physical information, server side key generation means 432 for generating server side random information using the decrypted device physical information, and public key encryption / decryption means in the registration phase The server physical random information is obtained by comparing the device physical information decrypted by 410 with the device physical information decrypted by the public key encryption / decryption means 410 in the authentication phase, and by collating the terminal 160. A server-side key verification unit 472, and the server-side key verification unit 472 and the terminal-side key verification unit 473 verify authentication processing by checking whether the terminal-side random information matches the server-side random information. I do.

  Each of the above embodiments also discloses a terminal authentication system described in the following (1) to (4).

  A terminal authentication system that includes a terminal (for example, the terminal 160 or the terminal 180) and a server (for example, the server 150 or the server 170), performs terminal registration processing in the registration phase, and performs terminal authentication processing in the authentication phase. The terminal uses a device physical information generation unit (for example, device physical information generation unit 480) that generates physical information related to the components of the terminal as device physical information, and a server public key (for example, server public key 421). Public key encryption means (for example, public key encryption means 411) that encrypts physical information and transmits it to the server, and terminal-side key generation means (for example, key generation means) that generates terminal-side random information using device physical information 431) and terminal side key verification means (for example, key verification means 471) for acquiring terminal side random information The server includes a public key encryption / decryption unit (for example, public key encryption / decryption unit 410) that decrypts the encrypted device physical information using a server secret key (for example, the server secret key 420), and Physical information storage means (for example, physical information storage means 450) for storing the decrypted device physical information, and server side key generation means (for example, for generating server side random information using the decrypted device physical information) The key generation unit 430) and the device physical information decrypted by the public key encryption / decryption unit in the registration phase and the device physical information decrypted by the public key encryption / decryption unit in the authentication phase are compared with each other. Collation means (for example, collation means 460) and server side key verification means (for example, key verification means 470) for acquiring server-side random information DOO wherein the server-side key verifying means and terminal key verification means, terminal authentication system to verify the authentication process by said terminal random information and the server-side random information to determine whether to match.

(2) The terminal authentication system includes a challenge generation unit (for example, a challenge generation unit) that generates a challenge that specifies a component used by the device physical information generation unit to generate device physical information in the registration phase and the authentication phase. Generation and storage means 500) may be included. According to such a terminal authentication system, the device physical information used for authentication is designated as a challenge by the server, so that the device physical information used for authentication can be updated.

(3) The terminal authentication system is configured such that the device physical information generation unit includes a ring oscillator circuit (for example, the ring oscillator circuit 600), and generates frequency information of the ring oscillator circuit as device physical information. It may be.

(4) In the terminal authentication system, the matching unit calculates a frequency ratio of the corresponding ring oscillator circuit in the registration phase and the authentication phase, and based on a statistical value (for example, standard deviation) of the ratio, You may be comprised so that collation may be performed.

  The present invention can be applied to device authentication.

DESCRIPTION OF SYMBOLS 100 Server 110 Terminal 120,480 Device physical information generation means 410 Public key encryption / decryption means 411 Public key encryption means 420 Server private key 421 Server public key 430,431 Key generation means 432 Server side key generation means 433 Terminal side key generation means 440, 441 Key storage unit 450 Physical information storage unit 460 Verification unit 470, 471 Key verification unit 472 Server side key verification unit 473 Terminal side key verification unit 500 Challenge generation and storage unit 600 Ring oscillator circuit 620 Counter 630 Memory

Claims (8)

A terminal authentication system comprising a terminal and a server, performing registration processing of the terminal in a registration phase, and performing authentication processing of the terminal in an authentication phase,
The terminal
Device physical information generating means for generating, as device physical information, physical information related to the components of the terminal;
Public key encryption means for encrypting the device physical information using a server public key and transmitting it to the server;
Terminal-side key generation means for generating terminal-side random information using the device physical information;
Terminal side key verification means for obtaining the terminal side random information,
The server
Public key encryption / decryption means for decrypting the encrypted device physical information using a server private key;
Physical information storage means for storing the decrypted device physical information;
Server-side key generation means for generating server-side random information using the decrypted device physical information;
The terminal physical verification is performed by comparing the device physical information decrypted by the public key encryption / decryption unit in the registration phase with the device physical information decrypted by the public key encryption / decryption unit in the authentication phase. Matching means;
Server-side key verification means for obtaining the server-side random information,
The server side key verification means and the terminal side key verification means are:
A terminal authentication system, wherein verification of authentication processing is performed by checking whether or not the terminal-side random information matches the server-side random information. The terminal authentication system according to claim 1, wherein the server includes challenge generation means for generating a challenge for designating a component used by the device physical information generation means to generate device physical information in the registration phase and the authentication phase. The terminal authentication system according to claim 1, wherein the device physical information generation unit includes a ring oscillator circuit and generates frequency information of the ring oscillator circuit as device physical information. The terminal authentication system according to claim 3, wherein the verification unit calculates a frequency ratio of the corresponding ring oscillator circuit in the registration phase and the authentication phase, and performs terminal verification based on a statistical value of the ratio. Using a terminal and a server, a terminal authentication method that performs registration processing of the terminal in a registration phase and performs authentication processing of the terminal in an authentication phase,
During the registration phase
The terminal
Generating physical information about the components of the terminal as device physical information;
Encrypt the device physical information using a server public key and send it to the server,
The server
Decrypting the encrypted device physical information using a server private key;
Storing the decrypted device physical information;
During the authentication phase,
The terminal
Generating physical information about the components of the terminal as device physical information;
Encrypt the device physical information using the server public key and send it to the server,
Generate terminal-side random information using the device physical information,
The server
Using the server private key, decrypt the encrypted device physical information,
Generate server-side random information using the decrypted device physical information,
The device physical information decrypted in the registration phase and the device physical information decrypted in the authentication phase are compared to perform verification of the terminal,
The terminal and the server are
A terminal authentication method comprising: verifying authentication processing by confirming whether the terminal-side random information matches the server-side random information. The terminal authentication method according to claim 5, wherein the server generates a challenge that specifies a component to be used for generating device physical information in the registration phase and the authentication phase. The terminal authentication method according to claim 5, wherein the terminal generates frequency information of the ring oscillator circuit as device physical information. The terminal authentication method according to claim 7, wherein the server calculates a frequency ratio of the corresponding ring oscillator circuit in the registration phase and the authentication phase, and performs terminal verification based on a statistical value of the ratio.

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