Information processing system, information processing device, information processing method, and recording medium

Abstract

An information processing system (100) includes a first conversion unit (117) and a second conversion unit (137). The first conversion unit (117) performs first conversion processing on biological information using a first key, to generate first post-conversion information. The second conversion unit (137) performs second conversion processing on the first post-conversion information using a second key, to generate second post-conversion information. The first conversion processing and the second conversion processing are performed in devices (110, 130) different from each other.

Description

Information processing system, information processing device, information processing method, and recording medium

[0001] The present disclosure relates to an information processing system, an information processing device, an information processing method, and a recording medium.

[0002] Biometric authentication, which uses biometric information that indicates an individual's unique characteristics, is becoming increasingly popular for authenticating individuals. However, since biometric information often remains largely unchanged throughout a person's lifetime, there is a risk that once biometric information is leaked, biometric authentication using that information will no longer be secure for the person's lifetime. To reduce the risk of biometric information leaks, biometric information protection technology has been proposed that performs matching on biometric information in its converted state.

[0003] For example, Patent Document 1 discloses a terminal device 10 that, when registering and matching biometric information, acquires a user's biometric information, encrypts the acquired biometric information in two stages using XOR (exclusive OR) and homomorphic encryption, and transmits the encrypted information to a calculation server 100.

[0004] According to Patent Document 1, when registering or verifying biometric information, the terminal device 10 acquires the user's biometric information using a sensor and generates a feature vector A or B as feature information based on the acquired biometric information. The terminal device 10 calculates an exclusive OR of the feature vector A or B and a user-specific random number R generated based on a password or the like specified by the user (i.e., performs XOR encryption) to calculate a first ciphertext. The terminal device 10 further encrypts the first ciphertext into a second ciphertext using an algorithm capable of calculating a Hamming distance (privacy distance) in an encrypted state, for example, a public key for homomorphic encryption, and transmits the second ciphertext to the calculation server 100.

[0005] According to Patent Document 1, when biometric information is registered, the calculation server 100 receives a second ciphertext from the terminal device 10 and stores the second ciphertext as registration information.

[0006] According to Patent Document 1, when matching biometric information, the calculation server 100 receives a second ciphertext from the terminal device 10 and calculates the Hamming distance between the second ciphertext and a second ciphertext stored as registration information at the time of registration in an encrypted state. The calculation server 100 transmits the calculated Hamming distance to the authentication server 200. Upon receiving the Hamming distance, the authentication server 200 decrypts it using a private key for homomorphic encryption.

[0007] Patent Documents 2 and 3 are other examples of documents that disclose techniques using homomorphic public key cryptography for biometric authentication.

[0008] JP 2015-139014 A International Publication No. 2016 / 203762 A JP 2017-009914 A

[0009] However, Patent Document 1 merely describes using the second ciphertext for matching, and does not disclose any technology for protecting biometric information in cases where, for example, multiple devices each manage a database and perform multiple matches to access each of the multiple databases.

[0010] For example, when the technology described in Patent Literature 1 is applied to multiple comparisons for accessing multiple databases, a series of processes from acquiring biometric information from a sensor to generating a second ciphertext must be executed for each comparison. As such, applying the technology described in Patent Literature 1 to multiple comparisons may be inefficient due to factors such as an increased processing load on the terminal device 10 and complicated control.

[0011] As described above, Patent Documents 2 and 3 are examples of documents that disclose technologies that use homomorphic public key cryptography for biometric authentication. Therefore, these documents also do not disclose technologies for protecting biometric information when performing matching to access each of multiple databases. When the technologies described in Patent Documents 2 and 3 are applied to multiple matchings, there is a risk that the same problems as when the technology described in Patent Document 1 is applied to multiple matchings may occur.

[0012] In view of the above-mentioned problems, an example of a purpose of this disclosure is to provide an information processing system, an information processing device, an information processing method, a recording medium, and the like that are capable of efficiently protecting biometric information.

[0013] According to one aspect of this disclosure, an information processing system is provided, comprising: a first conversion means that performs a first conversion process on biometric information using a first key to generate first converted information; and a second conversion means that performs a second conversion process on the first converted information using a second key to generate second converted information, wherein the first conversion process and the second conversion process are performed by different devices.

[0014] According to one aspect of this disclosure, an information processing device is provided, comprising: a first converted information acquisition means for acquiring, via a network, first converted information obtained by performing a first conversion process on biometric information; and a second conversion means for performing a second conversion process on the first converted information to generate second converted information.

[0015] According to one aspect of this disclosure, an information processing method is provided in which a first device performs a first conversion process on biometric information using a first key to generate first converted information, and a second device different from the first device performs a second conversion process on the first converted information using a second key to generate second converted information.

[0016] According to one aspect of this disclosure, a recording medium is provided having recorded thereon a program for causing a first device to perform a first conversion process on biometric information using a first key to generate first converted information, and causing a second device different from the first device to perform a second conversion process on the first converted information using a second key to generate second converted information.

[0017] According to one aspect of the present disclosure, it is possible to efficiently protect biometric information.

[0018] 1 is a diagram illustrating an overview of an information processing system according to a first embodiment. FIG. 2 is a diagram illustrating an overview of an information processing device (second device) according to the first embodiment. FIG. 3 is a diagram illustrating an overview of information processing according to the first embodiment. FIG. 4 is a diagram illustrating an example of permutation. FIG. 5 is a diagram illustrating an example of matrix transformation. FIG. 6 is a diagram illustrating an example of transformation using additive homomorphic encryption. FIG. 7 is a diagram illustrating an example of the physical configuration of a first device according to the first embodiment. FIG. 8 is a diagram illustrating an example of the configuration of an information processing system according to a second embodiment. FIG. 9 is a diagram illustrating an example of the functional configuration of a first key generation device according to the second embodiment. FIG. 10 is a diagram illustrating an example of the functional configuration of a second key generation device according to the second embodiment. FIG. 11 is a diagram illustrating an example of the functional configuration of a first device according to the second embodiment. FIG. 12 is a diagram illustrating an example of the functional configuration of a second device according to the second embodiment. FIG. 13 is a diagram illustrating an example of the functional configuration of a third device according to the second embodiment. FIG. 14 is a diagram illustrating an example of the functional configuration of a first update key generation device according to the second embodiment. FIG. 15 is a diagram illustrating an example of the functional configuration of a second update key generation device according to the second embodiment. FIG. 16 is a diagram illustrating an example of the flow of first key generation processing according to the second embodiment. FIG. 17 is a diagram illustrating an example of the flow of second key generation processing according to the second embodiment. FIG. 18 is a diagram illustrating an example of the flow of registration processing according to the second embodiment. FIG. 19 is a diagram illustrating an example of the flow of matching processing according to the second embodiment. FIG. 19 is a diagram illustrating an example of the flow of first key update processing according to the second embodiment. 1 is a diagram showing an example of the flow of second key update processing according to embodiment 2. FIG. 2 is a diagram showing an example of the configuration of an information processing system according to embodiment 3. FIG. 3 is a diagram showing an example of the configuration of an information processing system according to embodiment 4. FIG. 4 is a diagram showing an example of the functional configuration of a second key generation device according to embodiment 4. FIG. 5 is a diagram showing an example of the functional configuration of a second device according to embodiment 4. FIG. 6 is a diagram showing an example of the functional configuration of a third device according to embodiment 4. FIG. 7 is a diagram showing an example of the functional configuration of a second update key generation device according to embodiment 4. FIG. 8 is a diagram showing an example of the functional configuration of a decryption device according to embodiment 4. FIG. 9 is a diagram showing an example of the flow of second key generation processing according to embodiment 4. FIG. 10 is a diagram showing an example of the flow of registration processing according to embodiment 4. FIG. 11 is a diagram showing an example of the flow of matching processing according to embodiment 4. FIG. 12 is a diagram showing an example of the flow of matching processing according to embodiment 4. FIG. 13 is a diagram showing an example of the flow of first key update processing according to embodiment 4. FIG. 14 is a diagram showing an example of the flow of second key update processing according to embodiment 4.

[0019] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In all drawings, like components are designated by like reference numerals, and descriptions thereof will be omitted where appropriate.

[0020] 1 is a diagram showing an overview of an information processing system 100 according to embodiment 1. The information processing system 100 includes a first conversion unit 117 and a second conversion unit 137.

[0021] The first conversion unit 117 performs a first conversion process on the biometric information using a first key to generate first converted information. The second conversion unit 137 performs a second conversion process on the first converted information using a second key to generate second converted information.

[0022] The first conversion process and the second conversion process are performed by different devices 110 and 130 .

[0023] According to this information processing system 100, it is possible to efficiently protect biometric information.

[0024] 2 is a diagram showing an overview of the information processing device (second device) 130 according to embodiment 1. The information processing device 130 includes a first converted information acquisition unit 136 and a second conversion unit 137.

[0025] The first converted information acquisition unit 136 acquires, via the network NT, first converted information obtained by performing the first conversion process on the biometric information. As described above, the second conversion unit 137 performs the second conversion process on the first converted information using the second key to generate second converted information.

[0026] According to this information processing device 130, it is possible to efficiently protect biometric information.

[0027] FIG. 3 is a diagram illustrating an overview of information processing according to the first embodiment.

[0028] The first device 110 performs a first conversion process on the biometric information using a first key to generate first converted information (step S41). The second device 130, which is different from the first device 110, performs a second conversion process on the first converted information using a second key to generate second converted information (step S45).

[0029] This information processing makes it possible to efficiently protect biometric information.

[0030] A detailed example of the information processing system 100 according to the first embodiment will be described below.

[0031] In this embodiment, in order to verify the biometric information, the biometric information is converted in two stages by sequentially performing a first conversion process and a second conversion process on the biometric information, thereby enabling verification using each of the two pieces of converted information (i.e., the first converted information and the second converted information).

[0032] For biometric authentication, three or more pieces of converted information generated by sequentially converting biometric information in three or more stages may be used for matching. In this case, the conversion processes in each stage may be performed by different devices.

[0033] (Examples of Biometric Information) Biometric information is information that indicates individual-specific physical or behavioral features. Specific examples of biometric information include images of irises, faces, fingerprints, palm prints, etc., features extracted from the images, and features extracted from audio information such as voiceprints. Features may be extracted from images, audio, etc. using common techniques, for example.

[0034] Note that biometric information is typically human biometric information, but is not limited thereto and may be biometric information of animals such as dogs and snakes. Furthermore, the biometric information disclosed herein may be fuzzy information. Fuzzy information refers to information that changes slightly each time it is acquired, even if it is acquired from the same information source. Fuzzy information may be, for example, information about a semiconductor device that uses a PUF (Physically Unclonable Function). In this case, the information about the semiconductor device is, for example, information indicating individual differences between semiconductor devices such as IC (Integrated Circuit) chips. Individual differences between semiconductor devices occur during the manufacturing process of the semiconductor devices, and can be used to identify individual semiconductor devices. This disclosure may also be applied to other fuzzy information.

[0035] In this disclosure, an example will be described in which the biometric information is a numeric vector type biometric information. That is, the biometric information according to this disclosure is represented by a one-dimensional matrix (numeric vector) including N components (N is an integer equal to or greater than 1). Hereinafter, the numeric vector type biometric information including N components will also be referred to as a "biometric information vector." Note that the method of representing the biometric information is not limited to a numeric vector, and any appropriate method may be used.

[0036] (Example of Conversion Process) The conversion process is a process for generating converted information by converting biometric information. The conversion performed in the conversion process is a conversion for protecting the biometric information, and may be, for example, a conversion that changes at least a part of the input pre-conversion information. For example, the pre-conversion information in the first conversion stage is biometric information, and in the second and subsequent conversion stages, it is converted information obtained in the previous conversion process. This makes it difficult to identify the biometric information itself even if the converted information is leaked, thereby protecting the biometric information.

[0037] Furthermore, in the conversion process according to this disclosure, it is preferable to perform conversion so that the converted information can be used to compare the biometric information in its converted state. For example, general biometric information protection technology applied to protect biometric information in biometric authentication can be applied to such conversion.

[0038] Examples of general biometric information protection technologies applied in biometric authentication include cancelable biometric authentication technology (in the narrow sense) and confidential biometric authentication technology.

[0039] Cancellable biometric authentication technology is, for example, a technology that uses conversion to directly obtain a plaintext matching result by matching the converted information.

[0040] The confidential biometric authentication technology is a technology that uses a conversion to obtain an encrypted matching result by comparing, for example, the converted information. The confidential biometric authentication technology uses a public key and a private key. The public key is used, for example, to generate the converted information. Then, by performing a comparison using the converted information, the encrypted matching result can be obtained. The private key is used to decrypt the matching result.

[0041] In general, confidential biometric authentication technology provides a higher level of protection for biometric information than cancelable biometric authentication technology, but imposes a larger processing load.

[0042] Note that the terms cancelable biometric authentication technology and secret biometric authentication technology are sometimes used in general with meanings different from the above definitions, such as when cancelable biometric authentication technology is used in a broad sense as a general term for biometric information protection technology in biometric authentication. Therefore, the above definitions are examples for explaining this disclosure and are not intended to limit this disclosure.

[0043] In describing a detailed example of such a conversion, the following terms will be explained.

[0044] The "transformed information vector" is transformed information in the form of a numeric vector including N components. Note that the method of representing the transformed information is not limited to a numeric vector, and any appropriate method may be used.

[0045] The "registered information" is post-transformation information that is registered in advance. The "registered information vector" is registration information in the form of a numeric vector including N components, and can also be said to be a pre-registered post-transformation information vector.

[0046] The "matching information" is transformed information used for matching with the registered information. The "matching information vector" is a numerical vector type matching information including N components, and can also be said to be a transformed information vector used for matching with the registered information vector.

[0047] In other words, "post-conversion information" is a general term for "registration information" and "matching information." "Post-conversion information" may include at least one of registration information and matching information. Furthermore, "post-conversion information vector" is a general term for "registration information vector" and "matching information vector." "Post-conversion information vector" may include at least one of registration information vector and matching information vector.

[0048] Next, a "key" is information that defines parameters used in various processes. A "conversion key" is a key used in a conversion process. In the conversion process, for example, a calculation is performed using a function to convert pre-conversion information into post-conversion information. The conversion key defines at least some of the parameters used in this calculation. The conversion key may be generated, for example, using a random number.

[0049] The "registration key" is a conversion key used in the conversion process to generate registration information. The "verification key" is a conversion key used in the conversion process to generate verification information.

[0050] An "update key" is a key used to update a key. For example, when a conversion key is updated using an update key, at least some of the parameters used in the conversion process are changed to different values. The update key may be generated using, for example, random numbers.

[0051] The "registration update key" is a key used to update the registration key. The "verification update key" is a key used to update the verification key.

[0052] That is, the "conversion key" is a general term for the "registration key" and the "verification key." The "conversion key" may include at least one of the registration key and the verification key. Furthermore, the "update key" is a general term for the "registration update key" and the "verification update key." The "update key" may include at least one of the registration update key and the verification update key.

[0053] As described above, the private key is a key used to decrypt the encrypted matching result in the confidential biometric authentication technology. Therefore, the private key is also called a "decryption key."

[0054] (Examples of Cancellable Biometric Authentication Techniques) Examples of types of cancelable biometric authentication techniques include permutation and matrix transformation.

[0055] Component permutation is a transformation method in which the positions of at least some components of vector-type pre-transformation information are swapped (the order of the components is rearranged). －１The transformation method uses a registration key and a matching key, respectively, and multiplies these matrices by, for example, vector-type pre-transformation information. Examples of these will be described below with reference to the drawings.

[0056] (Example 1 of Cancellable Biometric Authentication Technology: Permutation) Fig. 4 is a diagram showing an example of permutation. A left-pointing arrow "←" indicates that the key written to the right of this symbol is applied to the information written to the left of this symbol, and this also applies hereinafter. In the example shown in the figure, pre-conversion information A ｐｒｅ , B ｐｒｅ , converted information A ａｆｔ , B ａｆｔ1 , B ａｆｔ2 Each of the elements is represented by a numerical vector containing N elements.

[0057] FIG. 4(a) shows the pre-conversion information A for registration. ｐｒｅ is converted using the conversion key S to obtain the converted information A for registration. ａｆｔ (=A ｐｒｅ 4(a) shows an example in which the already registered converted information for registration A is generated. ａｆｔ is the update key S Δ The updated converted information for registration A is updated using ａｆｔ_ｎｅｗ (=A ａｆｔ ←S Δ ) is generated as follows:

[0058] Update key S Δ After the conversion key S is updated by ａｆｔ When generating the updated conversion key S ｎｅｗ (=S←S Δ ) to obtain the pre-conversion information A for registration. ｐｒｅ It is recommended to convert the conversion key S ｎｅｗ is a conversion key S and an update key S for the pre-conversion information. Δ This is the key to performing the same transformation as when

[0059] 4(b) and 4(c) show the pre-conversion information B for verification before and after the conversion key S is updated. ｐｒｅ 4(b) shows an example of converting the pre-conversion information for verification B using the pre-update conversion key S. ｐｒｅ Convert the converted information for comparison B ａｆｔ1 (=Bｐｒｅ 4(c) shows an example in which the updated conversion key S ｎｅｗ Using the pre-conversion information B for comparison ｐｒｅ Convert the converted information for comparison B ａｆｔ2 (=B ｐｒｅ ←S ｎｅｗ ) is generated as follows:

[0060] The conversion key S shown in the figure includes moving the i-th component to the j-th component. Δ The conversion key S ｎｅｗ (=S←S Δ ) involves moving the i-th component to the k-th component, where i, j, and k are all integers between 1 and N, inclusive.

[0061] As can be seen from this example, in the component permutation, a conversion key S common to the registration key and the matching key may be used. Also, an update key S common to the registration update key and the matching update key may be used. Δ may be used.

[0062] When permutation is used, pre-transformation information A ｐｒｅ and pre-conversion information B ｐｒｅ The correspondence between each component and the converted information A ａｆｔ or A ａｆｔ_ｎｅｗ and converted information B ａｆｔ1 or B ａｆｔ2 By using an appropriate calculation method that utilizes this, the pre-conversion information A ｐｒｅ and pre-conversion information B ｐｒｅ and the converted information A ａｆｔ or A ａｆｔ_ｎｅｗ and converted information B ａｆｔ1 or B ａｆｔ2 The result of the calculation using the converted information A can be obtained by the calculation using the converted information B. ａｆｔ or A ａｆｔ_ｎｅｗ and converted information B ａｆｔ1 or B ａｆｔ2 and the pre-conversion information A ｐｒｅ and pre-conversion information B ｐｒｅ It is possible to obtain a matching result equivalent to that obtained using

[0063] (Example 2 of Cancellable Biometric Authentication Technology: Matrix Transformation) FIG. 5 is a diagram showing an example of matrix transformation. In the example shown in the figure, pre-transformation information A ｐｒｅ , B ｐｒｅ , converted information A ａｆｔ , B ａｆｔ1 , B ａｆｔ2 Each of the elements is represented by a numerical vector containing N elements.

[0064] FIG. 5(a) shows the pre-conversion information A for registration. ｐｒｅ is converted using the registration key M to obtain the converted information A for registration. ａｆｔ (=A ｐｒｅ ←M) is generated. ａｆｔ = M Ｔ ・A ｐｒｅ The subscript T denotes a transposed matrix, and the same applies hereinafter.

[0065] FIG. 5(a) further shows the already registered converted information A for registration. ａｆｔ is the registration update key M Δ The updated converted information for registration A is updated using ａｆｔ_ｎｅｗ (=A ａｆｔ ←M Δ ) is generated. For example, ａｆｔ_ｎｅｗ = M Δ Ｔ ・A ｐｒｅ holds true.

[0066] Registration update key M Δ After the registration key M is updated by ａｆｔ When generating the updated registration key M ｎｅｗ (= M←M Δ ) to obtain the pre-conversion information A for registration. ｐｒｅ It is advisable to convert the following. For example, A ａｆｔ_ｎｅｗ = M ｎｅｗ Ｔ ・A ｐｒｅ The registration key M ｎｅｗ For the pre-conversion information, the registration key M and the registration update key M Δ This is the key to perform the same transformation as when M is applied in sequence. ｎｅｗ = M.M. Δ , Mｎｅｗ Ｔ = M Δ Ｔ ・M Ｔ holds true.

[0067] 5(b) and (c) show the matching key M －１ Before and after the update, the pre-conversion information for comparison B ｐｒｅ Here is an example of converting

[0068] FIG. 5(b) shows the matching key M before updating. －１ Using the pre-conversion information B for comparison ｐｒｅ Convert the converted information for comparison B ａｆｔ1 (=B ｐｒｅ ←M －１ ) is generated. For example, B ａｆｔ1 = M －１ ・B ｐｒｅ holds true.

[0069] FIG. 5(c) shows the updated matching key M －１ ｎｅｗ Using the pre-conversion information B for comparison ｐｒｅ Convert the converted information for comparison B ａｆｔ2 (=B ｐｒｅ ←M －１ ｎｅｗ ) is generated. For example, B ａｆｔ2 = M －１ ｎｅｗ ・B ｐｒｅ The updated matching key M －１ ｎｅｗ is a matching key M －１ and the reconciliation key M Δ －１ and a key for performing the same transformation as when the registration key M ｎｅｗ is the inverse matrix of

[0070] As can be seen from this example, when matrix transformation is used, the pre-transformation information A ｐｒｅ and pre-conversion information B ｐｒｅ and the inner product of the transformed information A ａｆｔ or A ａｆｔ_ｎｅｗ and converted information B ａｆｔ1 or B ａｆｔ2 The inner product of is equal to. ａｆｔ , Bａｆｔ1 >=<M Ｔ ・A ｐｒｅ , M －１ ・B ｐｒｅ >=A ｐｒｅ Ｔ ・M.M. －１ ・B ｐｒｅ =A ｐｒｅ Ｔ ・B ｐｒｅ =<A ｐｒｅ , B ｐｒｅ > holds true. A ａｆｔ_ｎｅｗ and converted information B ａｆｔ2 The inner product of this equation is M and M －１ respectively. ｎｅｗ and M －１ ｎｅｗ It is better to replace it with

[0071] When matrix transformation is used, pre-transformation information A ｐｒｅ and pre-conversion information B ｐｒｅ and the converted information A ａｆｔ or A ａｆｔ_ｎｅｗ and converted information B ａｆｔ1 or B ａｆｔ2 The result of the calculation using the converted information A can be obtained by the calculation using the converted information B. ａｆｔ or A ａｆｔ_ｎｅｗ and converted information B ａｆｔ1 or B ａｆｔ2 and the pre-conversion information A ｐｒｅ and pre-conversion information B ｐｒｅ It is possible to obtain a matching result equivalent to that obtained using

[0072] In addition, the conversion key S and the update key S Δ The calculation using the registration key M and the registration update key M can also be realized as a calculation using a square matrix. Δ The matrices used as each of may be generated using random numbers as described above, but they are regular matrices, i.e., matrices whose inverse matrices exist. Therefore, if the matrices generated using random numbers are not regular matrices, the matrices may be recreated using newly generated random numbers, for example.

[0073] (Example of Confidential Biometric Authentication Technology) For example, public key cryptography that is homomorphic with respect to addition (e.g., additive homomorphic encryption, somewhat homomorphic encryption, fully homomorphic encryption) can be applied to the confidential biometric authentication technology. An example of such a type of confidential biometric authentication technology is Lifted-Elgamal encryption (also referred to as Modified-Elgamal encryption) (see, for example, Patent Documents 2 and 3).

[0074] Additive homomorphic encryption generally includes a key generation algorithm KeyGen, an encryption algorithm Enc, and a decryption algorithm Dec. These algorithms can be expressed as follows: The right-facing arrow "→" indicates that the information written to the right of this symbol is output in response to the input written to the left of this symbol, and the same applies hereinafter.

[0075] Key generation algorithm: KeyGen(1 ｋ ) → (PK, SK) Encryption algorithm: Enc(PK, m) → c Decryption algorithm: Dec(SK, c) → m

[0076] The key generation algorithm KeyGen is an algorithm for generating a public key PK and a private key SK, and generates a security parameter 1. ｋ Calculate the public key PK and the private key SK using the security parameter 1. ｋ is a bit string of k 1's, and is a parameter that determines the length of the public key and private key.

[0077] The encryption algorithm Enc is an algorithm for calculating a ciphertext c obtained by encrypting the message m using the public key PK and the message m.

[0078] The decryption algorithm Dec is an algorithm for calculating a decryption result m obtained by decrypting the ciphertext c using the secret key SK and the ciphertext c.

[0079] Public key cryptography is homomorphic when it satisfies the condition shown in the following equation 1.

[0080] Enc(PK,m １ #m ２ )=Enc(PK, m １) @ Enc (PK, m ２ )...(Formula 1)

[0081] Here, # and @ represent different binary operators. １ and m ２ Each of these represents a message.

[0082] Lifted-Elgamal encryption is an example of public key encryption (i.e., public key encryption with additive homomorphism) in which the binary operators "@" and "#" in Equation 1 are a multiplication operator and an addition (additive) operator, respectively.

[0083] The Lifted-Elgamal encryption satisfies Equation 2.

[0084] Enc(PK,m １ +m ２ )=Enc(PK, m １ ) × Enc(PK, m ２ )...(Formula 2)

[0085] Equation 2 indicates that the process of performing an operation on multiple plaintexts and then encrypting them is equivalent to the process of performing an operation on multiple ciphertexts obtained by encrypting each of the multiple plaintexts. Therefore, in additively homomorphic public key cryptography, for example, the process of performing an addition operation on multiple plaintexts and then applying an encryption algorithm is equivalent to the process of calculating the product of the ciphertexts obtained by encrypting each of the multiple plaintexts.

[0086] Furthermore, in the Lifted-Elgamal encryption, using Equation 2, Equation 3 holds for any constant C0.

[0087] Enc(PK, C0×m １ )=Enc(PK, m １ ) Ｃ０ ...(Formula 3)

[0088] Equation 3 indicates that the process of encrypting plaintext after multiplying it by a constant is equivalent to the process of exponentiating the ciphertext obtained by encrypting the plaintext.

[0089] Next, detailed examples of the key generation algorithm KeyGen, the encryption algorithm Enc, and the decryption algorithm Dec will be described.

[0090] For example, the key generation algorithm KeyGen includes the following steps 11 to 15.

[0091] Step 11: Security parameter 1 containing a value representing the length of the key to be generated ｋ Get.

[0092] Step 12: A group G whose order is a k-bit prime number p and its generator g are generated.

[0093] Step 13: Randomly select a value x from the set Zp, and calculate the generator g to the power x to obtain g. ｘ (=y) is calculated. Zp represents a set of integer values ​​from 1 to (p-1).

[0094] Step 14: Calculate a public key PK that is associated with the group G, the prime number p, the generator g, and the value y. The public key PK can be expressed as (G, p, g, y), for example.

[0095] Step 15: Calculate a private key SK associated with the public key PK and the value x. The private key SK can be expressed as (PK, x), for example.

[0096] For example, the encryption algorithm Enc includes the following steps 21 to 25.

[0097] Step 21: Obtain the public key PK and the message m.

[0098] Step 22: Randomly choose a value r from the set Zp.

[0099] Step 23: Calculate g by raising the generator g read from the public key PK to the rth power. ｒ (=c[1]) is calculated.

[0100] Step 24: The mth power of the generator g (= g ｍ ) and the value y read from the public key PK raised to the rth power (=y ｒ ) and the product g ｍ xy ｒ (=c[2]) is calculated.

[0101] Step 25: Calculate the ciphertext (c[1], c[2]) in which c[1] and c[2] calculated in steps 23 and 24 are associated.

[0102] If the encryption algorithm is Enc, the encryption algorithm including steps 21 to 25 can be expressed as Enc(PK, m) = (c[1], c[2]). (PK, m) is the public key PK and message m input to Enc. (c[1], c[2]) is the ciphertext (c[1], c[2]) output from Enc.

[0103] For example, the decryption algorithm Dec includes the following steps 31 to 33.

[0104] Step 31: Obtain the secret key SK (=((G, p, g, y), x)) and the ciphertext (c[1], c[2]).

[0105] Step 32: Using c[1] and c[2] read from the ciphertext and the value x read from the secret key SK, M(=c[2] / (c[1] ｘ )) where c[2] / (c[1] ｘ ) = g ｍ xy ｒ / ((g ｒ ) ｘ ) = g ｍ × ((g ｘ ) ｒ ) / ((g ｒ ) ｘ ) = g ｍ holds true.

[0106] Step 33: The decryption result m is calculated by taking the discrete logarithm of M with respect to the element g read from the private key SK.

[0107] The operator " / " represents an inverse element. For example, "1 / QA" represents the inverse element of QA. Also, for example, "QA / QB" represents the value obtained by multiplying QA by the inverse element of QB.

[0108] If the decryption algorithm is Dec, the decryption algorithm including steps 31 to 33 can be expressed as Dec(SK, c) = m, where (SK, c) is the public key PK and ciphertext (c[1], c[2]) input to Dec. m is the decryption result output from Dec.

[0109] It should be noted that the key generation algorithm KeyGen, the encryption algorithm Enc, and the decryption algorithm Dec are not limited to those exemplified here.

[0110] By using additive homomorphic encryption such as Lifted-Elgamal encryption, it is possible to perform addition and constant multiplication on multiple plaintexts without decrypting each of the multiple plaintexts, while keeping each of the multiple plaintexts as encrypted ciphertexts. The principle behind this will be explained with reference to Equations 6 and 7.

[0111] Let (G, p, g, y) denote the public key PK, m the message, mp the ciphertext obtained by encrypting the message m, and cp the ciphertext obtained by encrypting the message mp. According to the encryption algorithm, the ciphertexts c and cp shown in Equations 6 and 7 are calculated for the messages m and mp, respectively.

[0112] c=Enc(PK,m) =(c[1],c[2]) =(g ｒ , y ｒ ×g ｍ )...(Formula 6)

[0113] cp=Enc(PK, mp) =(cp[1],cp[2]) =(g ｒｐ , y ｒｐ ×g ｍｐ )...(Formula 7)

[0114] In this case, as shown in Equation 8, the encrypted value of the sum of a plurality of plaintexts is equal to the value obtained by multiplying each of the plurality of plaintexts by its encrypted value.

[0115] Enc(PK, m) * Enc(PK, mp) = (c[1] x cp[1], c[2] x cp[2]) = (g ｛ｒ＋ｒｐ｝ , y ｛ｒ＋ｒｐ｝ ×g ｛ｍ＋ｍｐ｝ )=Enc(PK,m+mp)...(Formula 8)

[0116] The operator "*" indicates that the value obtained by multiplying each element is calculated.

[0117] Furthermore, as shown in Equation 9, the encrypted value of the plaintext multiplied by a constant i is equal to the value obtained by raising the ciphertext obtained by encrypting the plaintext to the power of the constant i. However, the exponential power of the ciphertext represents an operation of raising each element included in the ciphertext to the exponential power.

[0118] Enc(PK, m) ｉ = (c[1] ｉ , c[2] ｉ ) = (g ｛ｉ×ｒ｝ , y ｛ｉ×ｒ｝ ×g ｛ｉ×ｍ｝ ) =Enc(PK, i×m)...(Formula 9)

[0119] Using such public key cryptography having additive homomorphism, pre-conversion information is converted to generate converted information, and matching can be performed on the converted information as is.

[0120] In the conversion using additive homomorphic encryption, the public key PK is used as a conversion key common to the registration information and the verification information. Since there is no need to distinguish between the registration key and the verification key, the public key PK is also referred to as the "conversion key PK." The private key SK is used as a key for decryption (decryption key), so it is also referred to as the "decryption key SK."

[0121] Furthermore, in transformation using additive homomorphic encryption, a common update key Δ can be used to update the registration information (ciphertext), the conversion key PK (public key), and the decryption key SK (secret key). In this way, in transformation using additive homomorphic encryption, the update key Δ does not need to be distinguished into a registration update key and a verification update key.

[0122] The update key Δ is obtained by randomly selecting a new value x from the set Zp in the same manner as in step 13 above. ｎｅｗ Then, the difference between the selected values ​​Δ(=x ｎｅｗ -x). Furthermore, proxy re-encryption, for example, may be used to update the registration information (ciphertext). Lifted-Elgamal encryption is an example of an encryption technology to which proxy re-encryption can be applied.

[0123] 6 is a diagram showing an example of a transformation using additive homomorphic encryption. In the example shown in the figure, pre-transformation information A ｐｒｅ , converted information A ａｆｔEach of the elements is represented by a numerical vector containing N elements.

[0124] FIG. 6 shows the pre-conversion information A for registration. ｐｒｅ is converted using the conversion key PK to obtain the converted registration information A ａｆｔ (=A ｐｒｅ 6 shows an example in which the already registered converted information A for registration is generated. ａｆｔ is updated using the update key Δ, and the updated registration converted information A ａｆｔ_ｎｅｗ (=A ａｆｔ ←Δ) is generated.

[0125] For example, the already registered converted information A ａｆｔ is (c[1], c[2]), then the converted information for registration A ａｆｔ_ｎｅｗ is (c[1],c[1] Δ × c[2]).

[0126] Although not shown, after the conversion key PK is updated by the update key Δ, the conversion information A for registration is ａｆｔ When generating the updated conversion key PK ｎｅｗ (=PK ｎｅｗ ←Δ) to obtain the pre-conversion information A for registration. ｐｒｅ It is recommended to convert the updated conversion key PK ｎｅｗ If the conversion key PK is (G, p, g, y), then (G, p, g, g Δ × y).

[0127] Regarding the decryption key SK, although not shown, for example, when the decryption key SK is (PK, x), the updated decryption key SK ｎｅｗ (PK ｎｅｗ , x+Δ).

[0128] When additive homomorphic encryption is used, the encrypted (converted) registration information A is ａｆｔ or A ａｆｔ_ｎｅｗ The result of the calculation of the information to be compared with the plaintext pre-conversion information A ｐｒｅ The result of the calculation (for example, the inner product) of the registered information A and the information to be checked can be equal to each other. ａｆｔ or A ａｆｔ_ｎｅｗand the information to be compared, the plaintext pre-conversion information A ｐｒｅ and the information to be compared, it is possible to obtain a matching result equivalent to that obtained when the above-mentioned information is used.

[0129] Note that various conversion processes (conversions) used in general biometric information protection techniques applied to biometric authentication are not limited to those exemplified here.

[0130] (Regarding the First Transformation Process and the Second Transformation Process) The first transformation process and the second transformation process may be either a transformation process used in general biometric information protection technology or a transformation process modified from the above. Using the above example, the first transformation process may be, for example, a permutation or a matrix transformation. The second transformation process may be, for example, a permutation, a matrix transformation, or a secret biometric authentication technology.

[0131] The first conversion process and the second conversion process are preferably different types of conversion processes. This allows the strength of protection of the biometric information to be different between the first converted information and the second converted information. Note that the first conversion process and the second conversion process may be the same type of conversion process.

[0132] The types of conversion processes may be distinguished by any suitable method, for example, according to the algorithm used in the conversion process.

[0133] (Regarding the first converted information and the second converted information) The first converted information and the second converted information are converted information generated by the first conversion process and the second conversion process, respectively. As described above, the converted information may include at least one of the registration information and the verification information.

[0134] As described above, by using the first post-conversion information and the second post-conversion information, it is possible to obtain a matching result equivalent to that obtained when using the respective pre-conversion information. Therefore, matching can be performed using each of the first post-conversion information and the second post-conversion information.

[0135] Such a check is useful, for example, when a different check method is used for each access (checking purpose) to a plurality of databases.

[0136] In particular, when the importance of multiple databases differs, the more important the database, the more likely it is that matching using post-conversion information obtained in a later conversion process will be applied to it. For example, when the second database is more important than the first database, matching using the first post-conversion information may be applied to the first database, and matching using the second post-conversion information may be applied to the second database.

[0137] To obtain post-conversion information in a later stage, it is necessary to go through a previous conversion process. Therefore, it is more difficult to identify pre-conversion information, etc. from post-conversion information obtained in a later conversion process than from post-conversion information obtained in an earlier conversion process. As a result, the more important a database is, the more difficult it is to access it by applying a match using post-conversion information obtained in a later conversion process. Therefore, it is possible to provide strong protection for databases according to their importance.

[0138] Note that managing access to a database is one example of a purpose for which matching is used (matching purpose). The purpose of matching is not limited to this, and may be, for example, access control to a compartment such as a room.

[0139] (Regarding the First Key and the Second Key) The first key and the second key are conversion keys corresponding to the types of the first conversion process and the second conversion process used, respectively. Each of the first key and the second key may include at least one of a registration key and a matching key. Furthermore, the first key and the second key may be commonly used for biometric information of different individuals.

[0140] (Example of Physical Configuration of Information Processing System 100 According to First Embodiment) The information processing system 100 physically includes, for example, a first device 110 and a second device 130 connected to each other via a network NT.

[0141] The network NT is a communication network that may be wired, wireless, or a combination of these. The first device 110 and the second device 130 are connected to each other via the network NT, and can transmit and receive information to and from each other via the network NT.

[0142] The first device 110 and the second device 130 are information processing devices that are physically configured in the same way. Here, an example of the physical configuration will be described using the first device 110 as an example, with reference to the drawings. Note that each device according to other embodiments may also be physically configured in the same way as the first device 110.

[0143] 7 is a diagram illustrating an example of the physical configuration of the first device 110 according to embodiment 1. The first device 110 physically includes, for example, a bus 1010, a processor 1020, a memory 1030, a storage device 1040, a network interface 1050, an input interface 1060, and an output interface 1070.

[0144] The bus 1010 is a data transmission path for transmitting and receiving data among the processor 1020, memory 1030, storage device 1040, network interface 1050, input interface 1060, and output interface 1070. However, the method of connecting the processor 1020 and the like to each other is not limited to bus connection.

[0145] The processor 1020 is implemented as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit).

[0146] The memory 1030 is a main storage device realized by a RAM (Random Access Memory) or the like.

[0147] The storage device 1040 is an auxiliary storage device realized by a hard disk drive (HDD), a solid state drive (SSD), a memory card, a read-only memory (ROM), or the like. The storage device 1040 stores program modules for realizing the functions of the device that includes the storage device 1040. The processor 1020 loads each of these program modules into the memory 1030 and executes them to realize the function corresponding to that program module.

[0148] The network interface 1050 is an interface for connecting a device equipped with the network interface 1050 to the network NT.

[0149] The input interface 1060 is an interface for the user to input information, and may be configured with, for example, a touch panel, a keyboard, a mouse, and the like.

[0150] The output interface 1070 is an interface for presenting information to the user, and may be configured, for example, by a liquid crystal panel, an organic EL (Electro-Luminescence) panel, or the like.

[0151] (Actions and Effects) As described above, according to this embodiment, the information processing system 100 includes the first conversion unit 117 and the second conversion unit 137. The first conversion unit 117 performs a first conversion process on the biometric information using a first key to generate first converted information. The second conversion unit 137 performs a second conversion process on the first converted information using a second key to generate second converted information. The first conversion process and the second conversion process are performed by different devices 110 and 130.

[0152] This allows the first converted information and the second converted information to be obtained in sequence from one biometric feature using different devices, and matching can be performed using each of them, thereby making it possible to efficiently protect biometric information.

[0153] Furthermore, since the second converted information is generated through a two-stage conversion process, it is difficult to identify pre-conversion information, etc., and personal information can be protected more safely than converted information that has undergone only a single stage of conversion process. Furthermore, since the first conversion process and the second conversion process are performed on different devices, the first key and the second key can be stored separately in different devices. Therefore, it is possible to safely protect biometric information.

[0154] According to this embodiment, the first conversion process and the second conversion process include different types of conversion processes.

[0155] This allows the strength of protection of biometric information to be changed between the first converted information and the second converted information. Generally, conversion processes that provide a strong level of protection for biometric information often result in a large processing load and a long processing time. By changing the strength of protection for biometric information, it is possible to select an appropriate conversion process depending on the level of protection for biometric information (security of biometric information) and the processing load or speed (efficiency) allowed for matching using converted information. Therefore, it is possible to protect biometric information efficiently and safely.

[0156] According to this embodiment, the first key and the second key are commonly used for biometric information of different individuals.

[0157] This allows the matching process to be performed without the need for the individual to perform an operation to identify the key corresponding to the individual, such as inputting an ID, each time matching is performed, thereby making it possible to efficiently protect biometric information.

[0158] <Embodiment 2> As described in embodiment 1, any type of conversion process used in general biometric information protection technology applied to biometric authentication may be adopted for each of the "first conversion process" and the "second conversion process". Embodiment 2 will be described using a detailed example in which "component permutation" is used for the "first conversion process" and "matrix transformation" is used for the "second conversion process". Therefore, in the detailed example according to this embodiment, the "first conversion key" becomes the "conversion key" in the "component transformation". Furthermore, in the detailed example according to this embodiment, the "second conversion key" becomes the "conversion key" in the "matrix transformation" (i.e., the "registration key" and the "verification key").

[0159] In this embodiment, for the sake of simplicity, descriptions that overlap with those in the first embodiment will be omitted as appropriate.

[0160] (Example of Functional Configuration of Information Processing System 200 According to Second Embodiment) FIG. 8 is a diagram showing an example of the configuration of an information processing system 200 according to the second embodiment.

[0161] The information processing system 200 is a system that sequentially performs a first conversion process and a second conversion process on biometric information to generate first converted information and second converted information, and performs matching using each of the first converted information and the second converted information.

[0162] The information processing system 200 includes, for example, a first key generation device 201a, a second key generation device 201b, a first device 210, a second device 230, a third device 250, a first update key generation device 270a, and a second update key generation device 270b.

[0163] (Example of Functional Configuration of First Key Generation Device 201a According to Second Embodiment) FIG. 9 is a diagram showing an example of the functional configuration of a first key generation device 201a according to the second embodiment.

[0164] The first key generation device 201a is an information processing device that generates a first conversion key. In a detailed example according to this embodiment, the first conversion key is the "conversion key S" in the "component conversion." The first key generation device 201a functionally includes, for example, a first key generation unit 204a and a first key transmission unit 205a. The processing performed by these functional components will be described later in the operation section.

[0165] (Example of Functional Configuration of Second Key Generation Device 201b According to Second Embodiment) FIG. 10 is a diagram showing an example of the functional configuration of a second key generation device 201b according to the second embodiment.

[0166] The second key generation device 201b is an information processing device that generates a second conversion key. The second conversion key in the detailed example according to this embodiment is a "conversion key M, M" in "matrix conversion." －１ The second key generation device 201b functionally comprises, for example, a second key generation unit 204b and a second key transmission unit 205b. The processes performed by these functional components will be described later in the section on operation.

[0167] (Example of Functional Configuration of First Device 210 According to Second Embodiment) FIG. 11 is a diagram showing an example of the functional configuration of the first device 210 according to the second embodiment.

[0168] The first device 210 is an information processing device that stores a first conversion key and performs component permutation on biometric information using the first conversion key to generate first converted information. Functionally, the first device 210 includes, for example, a first key storage unit 211, a first key acquisition unit 212, a biometric information acquisition unit 216, a first conversion unit 217, and a first key update unit 221.

[0169] The first converted information includes at least one of first registration information used as registration information and first verification information used as verification information.

[0170] The first key storage unit 211 is a storage unit for storing the first conversion key.

[0171] The processing performed by the other functional components will be described later in the section on operation.

[0172] (Example of Functional Configuration of Second Device 230 According to Second Embodiment) FIG. 12 is a diagram showing an example of the functional configuration of the second device 230 according to the second embodiment.

[0173] The second device 230 is an information processing device that stores a second conversion key and performs matrix transformation on the first converted information using the second conversion key to generate second converted information. The second device 230 also performs a matching process (first matching process) using the first converted information.

[0174] The second device 230 functionally comprises, for example, a second key memory unit 231, a second key acquisition unit 232, a first registration information memory unit 235, a first converted information acquisition unit 236, a second conversion unit 237, a first comparison unit 238, a first update key transfer unit 241, a second key calculation unit 242, a first registration information update unit 243, and a second key update unit 245.

[0175] The second converted information includes at least one of second registration information used as registration information and second verification information used as verification information.

[0176] The second key storage unit 231 is a storage unit for storing the second conversion key.

[0177] The first registration information storage unit 235 is a storage unit for storing the first registration information.

[0178] The processing performed by the other functional components will be described later in the section on operation.

[0179] (Example of Functional Configuration of Third Device 250 According to Second Embodiment) FIG. 13 is a diagram showing an example of the functional configuration of the third device 250 according to the second embodiment.

[0180] The third device 250 is an information processing device that performs a matching process (second matching process) using the second converted information.

[0181] The third device 250 includes a second registration information storage unit 251 , a second converted information acquisition unit 252 , a second collation unit 253 , a second update key transfer unit 254 , and a second registration information update unit 255 .

[0182] The second registration information storage unit 251 is a storage unit for storing second registration information.

[0183] The processing performed by the other functional components will be described later in the section on operation.

[0184] (Example of Functional Configuration of First Update Key Generation Device 270a According to Second Embodiment) FIG. 14 is a diagram showing an example of the functional configuration of a first update key generation device 270a according to the second embodiment.

[0185] The first update key generation device 270a is an information processing device that generates a first update key. The first update key in the detailed example according to this embodiment is the "update key S Δ "

[0186] The first update key generation device 270a functionally comprises, for example, a first update key generation unit 274a and a first update key transmission unit 275a. The processes performed by these functional components will be described later in the operation section.

[0187] (Example of Functional Configuration of Second Update Key Generation Device 270b According to Second Embodiment) FIG. 15 is a diagram showing an example of the functional configuration of the second update key generation device 270b according to the second embodiment.

[0188] The second update key generation device 270b is an information processing device that generates a second update key. The second update key in the detailed example according to this embodiment is the "update key M Δ , M Δ －１ ". That is, "Update key M Δ " and "Update key M Δ －１ " are examples of a "second registration update key" and a "second reconciliation update key", respectively. Note that the second update key may be either the second registration update key or the second reconciliation update key.

[0189] The second update key generation device 270b functionally includes, for example, a second update key generation unit 274b and a second update key transmission unit 275b. The processes performed by these functional components will be described later in the operation section.

[0190] (Example of operation of information processing system 200 according to embodiment 2) The information processing system 200 according to embodiment 2 executes information processing including first key generation processing, second key generation processing, registration processing, matching processing, first key update processing, and second key update processing.

[0191] (Example of First Key Generation Processing According to Embodiment 2) FIG. 16 is a diagram showing an example of the flow of first key generation processing according to embodiment 2. The first key generation processing is processing for generating and storing a first conversion key. The first key generation processing is started, for example, when the first key generation device 201a receives a predetermined instruction from an operator or the like. Note that the trigger for starting the first key generation processing is not limited to this.

[0192] The first key generation unit 204a generates a first conversion key using, for example, a random number (step S101a).

[0193] The first conversion key is a collective term for the first registration key, which is a registration key, and the first matching key, which is a matching key. As described above, the first conversion key in the detailed example according to this embodiment is the "conversion key" in the "component conversion". Therefore, the first conversion key in the detailed example according to this embodiment is a conversion key S that is common to the first registration key and the first matching key. In other words, the conversion key S in the detailed example according to this embodiment functions as the first registration key when used to generate registration information, and functions as the first matching key when used to generate matching information. Note that the first conversion key may be any key appropriate for the type of conversion process, and for example, the first registration key and the first matching key may be different keys.

[0194] For example, the first key generation unit 204a determines a conversion key S that represents a method for permuting components of a biometric information vector in accordance with a random number and a predetermined rule. The first key generation unit 204a sets the determined conversion key S as the first conversion key.

[0195] The random numbers are, for example, true random numbers or pseudo-random numbers generated by a random number generator. The random number generator may be configured using either hardware or a software program.

[0196] The first key transmitting unit 205a transmits the first conversion key generated in step S101a (step S102a).

[0197] For example, the first key sending unit 205 a sends the first conversion key to the first device 210 .

[0198] The first key acquisition unit 212 acquires the first conversion key transmitted in step S102a (step S103a).

[0199] The first key acquisition unit 212 stores the conversion key S acquired in step S103a in the first key storage unit 211 (step S104a), and ends the first key generation process. This allows the first registration key and the first verification key to be generated and stored in advance.

[0200] (Example of Second Key Generation Processing According to Embodiment 2) FIG. 17 is a diagram showing an example of the flow of second key generation processing according to embodiment 2. The second key generation processing is processing for generating and storing a second conversion key. The second key generation processing is started, for example, when the second key generation device 201b receives a predetermined instruction from an operator or the like. Note that the trigger for starting the second key generation processing is not limited to this.

[0201] The second key generation unit 204b generates a second conversion key using, for example, a random number (step S101b).

[0202] The second conversion key is a collective term for the second registration key, which is a registration key, and the second matching key, which is a matching key. As described above, the second conversion key in the detailed example according to this embodiment is a "conversion key" in "matrix conversion". Therefore, the second registration key in the detailed example according to this embodiment is a conversion key M, M which is different between the second registration key and the second matching key. －１ The second conversion key may be any key that corresponds to the type of conversion process, and for example, the second registration key and the second verification key may be a common key.

[0203] For example, the second key generation unit 204b determines a regular matrix M using random numbers and a predetermined rule. The second key generation unit 204b uses the determined regular matrix M as a second registration key and generates an inverse matrix M of M. －１ is the second matching key.

[0204] The random numbers are, for example, true random numbers or pseudo-random numbers generated by a random number generator. The random number generator may be configured using either hardware or a software program.

[0205] The second key transmitting unit 205b transmits the second conversion key generated in step S101b (step S102b). The second key transmitting unit 205b transmits the second conversion key to the second device 230, for example.

[0206] The second key acquisition unit 232 acquires the second conversion key transmitted in step S102b (step S103b).

[0207] The second key acquisition unit 232 stores the second conversion key acquired in step S103b in the second key storage unit 231 (step S104b), and ends the second key generation process. This allows the second conversion key to be generated and stored in advance.

[0208] (Example of Registration Processing According to Embodiment 2) Fig. 18 is a diagram showing an example of the flow of registration processing according to embodiment 2. The registration processing is processing for registering first registration information and second registration information in advance. The registration processing is started, for example, when the second key generation device 201b receives a predetermined registration instruction from an individual or the like who wishes to register. Note that the trigger for starting the registration processing is not limited to this.

[0209] The biometric information acquisition unit 216 acquires biometric information (step S120).

[0210] For example, the biometric information acquiring unit 216 acquires sensor information from a sensor (not shown), and generates a biometric information vector using the acquired sensor information.

[0211] The sensor may include at least one of a camera that photographs an individual, a microphone that captures the individual's voice, a fingerprint sensor that captures a fingerprint, and the like, and may output sensor information.

[0212] The sensor information may include information corresponding to predetermined biometric information used for matching. For example, if the sensor is a camera, the sensor information may include an image of an individual (e.g., an iris image, a face image, etc.). For example, if the sensor is a microphone, the sensor information may include the individual's voice. For example, if the sensor is a fingerprint sensor, the sensor information may be information indicating the individual's fingerprint.

[0213] The sensor may be built into first device 210. The sensor may be provided outside first device 210 and connected to first device 210 via a line configured by wired or wireless means or a combination of wired and wireless means.

[0214] The first conversion unit 217 uses the first registration key stored in the first key memory unit 211 to perform a first conversion process on the biometric information acquired in step S120 to generate first registration information (step S121).

[0215] For example, the first conversion unit 217 generates the first registration information by performing component permutation on the biometric information using the first registration key, a conversion key S. When the biometric information is a numeric vector including N components, the first registration information is also a numeric vector including N components.

[0216] The first conversion unit 217 transmits the first registration information generated in step S121 (step S122).

[0217] For example, the first conversion unit 217 transmits the first registration information to the second device 230 .

[0218] The first converted information acquisition unit 236 acquires the first registration information transmitted in step S122 (step S123).

[0219] The first converted information acquisition unit 236 stores the first registered information acquired in step S123 in the first registered information storage unit 235 (step S124).

[0220] The second conversion unit 237 uses the second registration key stored in the second key memory unit 231 to perform a second conversion process on the first registration information acquired in step S123 to generate second registration information (step S125).

[0221] For example, the second conversion unit 237 generates the second registration information by performing matrix transformation on the first registration information using the second registration key, that is, registration key M. When the biometric information is a numeric vector including N components, for example, the second registration information is also a numeric vector including N components.

[0222] The second conversion unit 237 transmits the second registration information generated in step S125 (step S126).

[0223] For example, the second conversion unit 237 transmits the second registration information to the third device 250 .

[0224] The second converted information acquisition unit 252 acquires the second registration information transmitted in step S126 (step S127).

[0225] The second converted information acquisition unit 252 stores the second registration information acquired in step S127 in the second registration information storage unit 251 (step S128), and ends the registration process.

[0226] This allows the first registration information and the second registration information to be registered using one piece of biometric information. By registering the first registration information and the second registration information in advance, two-stage verification can be performed in the verification process described below. Since the first conversion process and the second conversion process are performed in different devices 210 and 230, the conversion key S and the registration key M can be stored separately in different devices 210 and 230. This makes it possible to protect the biometric information efficiently and safely.

[0227] (Example of matching process according to embodiment 2) Fig. 19 is a diagram showing an example of the flow of the matching process according to embodiment 2. The matching process is a process for performing matching using each of the first matching information and the second matching information. The matching process is started, for example, when the second key generation device 201b receives a predetermined matching instruction from an individual or the like who desires matching. Note that the trigger for starting the matching process is not limited to this.

[0228] The biometric information acquisition unit 216 acquires biometric information (step S140).

[0229] Step S140 may be performed in the same manner as step S120.

[0230] The first conversion unit 217 uses the first matching key stored in the first key storage unit 211 to perform a first conversion process on the biometric information acquired in step S140 to generate first matching information (step S141).

[0231] For example, the first conversion unit 217 generates the first matching information by performing component permutation on the biometric information using the conversion key S, which is the first matching key. If the biometric information is a numeric vector including N components, the first matching information vector is also a numeric vector including N components.

[0232] The first conversion unit 217 transmits the first matching information generated in step S141 (step S142).

[0233] For example, the first conversion unit 217 transmits the first matching information to the second device 230 .

[0234] The first converted information acquisition unit 236 acquires the first matching information transmitted in step S142 (step S143).

[0235] The first matching unit 238 performs a first matching process (step S144) using the first registration information that has been registered in advance (i.e., stored in the first registration information storage unit 235) and the first matching information acquired in step S143.

[0236] The result of the first matching process (first matching result) is, for example, an evaluation value (first evaluation value) indicating the likelihood that the matched enrollment information and matching information originate from the same person. In the first matching process, calculations are performed using the enrollment information and matching information to obtain the first evaluation value. The first evaluation value is, for example, a similarity (first similarity) indicating the degree of similarity between the matched enrollment information and matching information. The first similarity is, for example, the dot product of the matched numeric vector-type enrollment information and matching information. As described above, the first similarity is equal to the dot product between the biometric information vectors acquired in steps S120 and S140, respectively.

[0237] For example, the first authentication may be performed based on a comparison result between the first evaluation value and a predetermined first threshold. The result of the first authentication is whether or not the matched first registration information and the first matching information are from the same person. For example, if the second device 130 manages a database, the second device 130 may determine whether or not to allow access to the database based on the result of the first authentication. Furthermore, the result of the first authentication may be transmitted to another device (not shown) and used by the other device.

[0238] Note that multiple pieces of first registration information may be registered in advance, and the first matching process may be performed for each piece of first registration information. That is, the first matching unit 238 may match each piece of first registration information with the first matching information. Furthermore, the similarity is not limited to the dot product. Examples of similarity other than the dot product will be described later as modified examples.

[0239] The second conversion unit 237 uses the second matching key stored in the second key memory unit 231 to perform a second conversion process on the first matching information acquired in step S143 to generate second matching information (step S145).

[0240] For example, the second conversion unit 237 converts the second matching key M －１ The second matching information is generated by performing matrix transformation on the first matching information using the following equation: When the biometric information is a numeric vector including N components, the second matching information is also a numeric vector including N components.

[0241] The second conversion unit 237 transmits the second matching information generated in step S145 (step S146).

[0242] For example, the second conversion unit 237 transmits the second matching information to the third device 250 .

[0243] The second converted information acquisition unit 252 acquires the second matching information transmitted in step S146 (step S147).

[0244] The second verification unit 253 performs a second verification process (step S148) using the second registration information registered in advance (i.e., stored in the second registration information storage unit 251) and the second verification information acquired in step S147, and then ends the verification process. There may be multiple pieces of second registration information. In this case, in the second verification process, a verification process may be performed between each of the multiple pieces of second registration information and the second verification information.

[0245] The result of the second matching process (second matching result) is, for example, an evaluation value (second evaluation value) indicating the likelihood that the matched registration information and matching information originate from the same person. In the second matching process, calculations are performed using the registration information and matching information to obtain the second evaluation value. The second evaluation value is, for example, a similarity (second similarity) indicating the degree of similarity between the matched registration information and matching information. The second similarity is, for example, the dot product of the matched numeric vector-type registration information and matching information. As will be understood from the description of the first embodiment, the second similarity is equal to the dot product between the biometric information vectors acquired in steps S120 and S140, respectively.

[0246] For example, the second authentication may be performed based on a comparison result between the second evaluation value and a predetermined second threshold. The result of the second authentication is whether or not the matched second registration information and the second matching information are from the same person. For example, if the third device 250 manages a database, the third device 250 may determine whether or not to allow access to the database based on the result of the second authentication. Furthermore, the result of the second authentication may be transmitted to another device (not shown) and used by the other device.

[0247] Note that a plurality of pieces of second registration information may be registered in advance, and the second matching process may be performed for each piece of second registration information. That is, the second matching unit 253 may match each piece of second registration information with the second matching information.

[0248] By performing such a matching process, first matching information and second matching information can be generated from one piece of biometric information, and two-stage matching can be performed using each of them. In addition, since the first conversion process and the second conversion process are performed by different devices 210 and 230, the conversion key S and the matching key M －１can be stored separately in different devices 210 and 230. Therefore, it is possible to protect the biometric information efficiently and safely.

[0249] (Example of First Key Update Processing According to Second Embodiment) FIG. 20 is a diagram showing an example of the flow of first key update processing according to the second embodiment.

[0250] The first key update process is a process for updating the first conversion key and the first registration information generated by conversion using the first conversion key. The first key update process is started, for example, when a predetermined time (for example, a fixed time on a predetermined day of each month) arrives or when the first update key generation device 270a receives a predetermined instruction from an operator, etc. Note that the trigger for starting the first key update process is not limited to these.

[0251] The first update key generating unit 274a generates a first update key using, for example, a random number (step S161).

[0252] The first update key is a key used to update the first conversion key, and is a collective term for the first registration update key used to update the first registration key and the first verification update key used to update the first matching key. As described above, the first conversion key in the detailed example according to this embodiment is the "conversion key" in the "component conversion", and is the conversion key S common to the first registration key and the first matching key. Therefore, the first update key in the detailed example according to this embodiment is the update key S common to the first registration update key and the first matching key. Δ The first update key may be any key corresponding to the first conversion key, and for example, the first registration update key and the first verification update key may be different keys.

[0253] For example, the first update key generation unit 274a generates a first update key S representing a method for replacing components of a biometric information vector in accordance with a predetermined rule using random numbers. Δ Determine.

[0254] The random numbers are, for example, true random numbers or pseudo-random numbers generated by a random number generator. The random number generator may be configured using either hardware or a software program.

[0255] The first update key transmitting unit 275a transmits the first update key generated in step S161 (step S162).

[0256] For example, the first update key transmitting unit 275 a transmits the first update key to the second device 230 .

[0257] The first update key transfer unit 241 acquires the first update key transmitted in step S162 (step S163).

[0258] The second key calculation unit 242 updates the current second conversion key using the first update key acquired in step S163 (step S164).

[0259] For example, the second key calculation unit 242 calculates the first update key S Δ The second key calculation unit 242 calculates the product of the inverse transformation key of the second key M and the second registration key M stored in the second key storage unit 231 to obtain a new second registration key M. The second key calculation unit 242 calculates the inverse matrix of the new second registration key M to obtain a new second verification key M. －１ The second key calculation unit 242 obtains the new second registration key M and the new second verification key M. －１ is stored in the second key storage unit 231. As a result, the current second conversion keys M and M －１ are the new second conversion keys M, M －１ will be updated to.

[0260] The first update key S Δ The current second conversion keys M and M are －１ to generate new second conversion keys M, M －１ The method for calculating is not limited to this.

[0261] The first registration information update unit 243 updates the first registration information stored in the first registration information storage unit 235 using the first update key acquired in step S163 (step S165).

[0262] For example, the first registration information update unit 243 updates the first update key S Δ The first registration information update unit 243 converts the first registration information using the first update key S to obtain new first registration information. The first registration information update unit 243 stores the new first registration information in the first registration information storage unit 235. As a result, the first registration information update unit 243 obtains the first update key S Δto update the current first registration information.

[0263] The first update key transfer unit 241 transmits the first update key acquired in step S163 (step S166).

[0264] For example, the first update key transfer unit 241 transmits the first update key to the first device 210 .

[0265] When the first key update unit 221 acquires the first update key transmitted in step S166, it uses the acquired first update key to update the first conversion key stored in the first key memory unit 211 (step S167), and terminates the first key update process.

[0266] For example, the first key update unit 221 updates the current first conversion key S as a first update key S Δ and update it to a new first conversion key S ｎｅｗ The first key update unit 221 calculates the calculated first conversion key S ｎｅｗ is stored in the first key storage unit 211. As a result, the first key update unit 221 stores the first update key S Δ The first conversion key S is updated using the following formula:

[0267] By performing such a first key update process, the first conversion key, the second conversion key, and the first registration information can be updated without changing the second registration information stored in the third device 250.

[0268] Note that the first key update process is not limited to the above example. In the first key update process according to this embodiment, an example has been described in which the second device 230 (first update key transfer unit 241) acquires the first update key from the first update key generation device 270a (first update key transmission unit 275a) (step S163) and transmits it to the first device 210 (step S166). For example, instead of steps S163 and S166, each of the first device 210 and the second device 230 may directly acquire the first update key from the first update key generation device 270a (e.g., the first update key transmission unit 275a).

[0269] (Example of Second Key Update Processing According to Second Embodiment) FIG. 21 is a diagram showing an example of the flow of second key update processing according to the second embodiment.

[0270] The second key update process is a process for updating the second conversion key and the second registration information generated by conversion using the second conversion key. The second key update process is started, for example, when a predetermined time (for example, a fixed time on a predetermined day of each month) arrives or when the second update key generation device 270b receives a predetermined instruction from an operator, etc. Note that the trigger for starting the first key update process is not limited to this.

[0271] The second update key generating unit 274b generates a second update key using, for example, a random number (step S171).

[0272] The second update key is a key used to update the second conversion key, and is a general term for the second registration update key used to update the second registration key and the second verification update key used to update the second verification key. As described above, the second conversion key in the detailed example according to this embodiment is the "transformation key" in the "matrix transformation". Therefore, the second update key in the detailed example according to this embodiment is an update key M that is different between the first registration update key and the first verification update key. Δ , M Δ －１ The second update key may be any key corresponding to the second conversion key, and for example, the second registration update key and the second verification update key may be a common key.

[0273] For example, the second update key generation unit 274b generates a second registered update key M Δ The second update key generation unit 274b generates the second registered update key M Δ By calculating the inverse matrix of the second reconciliation update key M Δ －１ Generate.

[0274] The random numbers are, for example, true random numbers or pseudo-random numbers generated by a random number generator. The random number generator may be configured using either hardware or a software program.

[0275] The second update key M Δ , M Δ －１ The method for generating the second registered update key M is not limited to this. For example, Δ The second device 230 generates the second registration update key MΔ , and the second reconciliation update key M Δ －１ may be generated.

[0276] The second update key transmitting unit 275b transmits the second update key generated in step S171 (step S172).

[0277] For example, the second update key transmitting unit 275 b transmits the second update key to the third device 250 .

[0278] The second update key transfer unit 254 acquires the second update key transmitted in step S172 (step S173).

[0279] The second registration information update unit 255 updates the second registration information stored in the second registration information storage unit 251 using the second update key acquired in step S173 (step S174).

[0280] For example, the second registration information update unit 255 updates the second registration update key M Δ The second registration information update unit 255 converts the current second registration information using the second registration update key M to calculate new second registration information. The second registration information update unit 255 stores the new second registration information in the second registration information storage unit 251. As a result, the second registration information update unit 255 calculates the second registration update key M Δ The second registration information is updated using the

[0281] The second update key transfer unit 254 transmits the second update key acquired in step S173 (step S175).

[0282] For example, the second update key transfer unit 254 transmits the second update key to the second device 230 .

[0283] When the second key update unit 245 acquires the second update key transmitted in step S175, it uses the acquired second update key to update the second conversion key stored in the second key memory unit 231 (step S176), and terminates the second key update process.

[0284] For example, the second key update unit 245 updates the current second conversion keys M, M －１ is the second update key M Δ , M Δ －１ and update it to a new second conversion key Mｎｅｗ , M ｎｅｗ －１ The second key update unit 245 calculates the calculated new second conversion key M ｎｅｗ , M ｎｅｗ －１ is stored in the second key storage unit 231. As a result, the second key update unit 245 stores the second update key M Δ , M Δ －１ The current second conversion keys M and M are －１ The method by which the second update unit 245 obtains the second update key is not limited to the example described here. For example, the second update unit 245 may obtain the second update key directly from the second update key generation device 270b. In this case, the third device 250 (for example, the second update key transfer unit 254) updates the second verification update key M Δ －１ without acquiring the second registration update key M Δ Only the

[0285] By performing such second key update processing, it is possible to update only the second conversion key and the second registration information independently of the first conversion key and the first registration information.

[0286] The second key update process is not limited to the above example. For example, in the second key update process according to this embodiment, an example has been described in which the third device 250 (second update key transfer unit 254) acquires the second update key from the second update key generation device 270b (second update key transmission unit 275b) (step S173) and transmits it to the second device 230 (step S175). Instead of steps S173 and S175, each of the second device 230 and the third device 250 may directly acquire the second update key from the second update key generation device 270b (second update key transmission unit 275b). In this case, the third device 250 stores the second verification update key M Δ －１ is not transmitted, and the second registration update key M Δ may be transmitted.

[0287] Furthermore, the first key update process and the second key update process may be performed at the same time, or may be performed at different times as needed. For example, the first conversion key and the second conversion key may be updated at the same time or at different times at a predetermined update time (e.g., periodically). Furthermore, for example, if there is a risk that one of the first conversion key and the second conversion key has been leaked, only the first conversion key or the second conversion key that is likely to have been leaked may be updated.

[0288] As described above, in the first key update process, when the first conversion key is updated, the first registration information is updated without updating the second registration information. In the second key update process, when the second conversion key is updated, the second registration information is updated without updating the first registration information.

[0289] That is, when either the first conversion key (corresponding to the first key) or the second conversion key (corresponding to the second key) is updated, only the registration information converted using either the first conversion key or the second conversion key to be updated is updated for the first registration information and the second registration information. As described above, the first registration information and the second registration information are information that has been converted using the first conversion key and the second conversion key, respectively, and registered in advance.

[0290] This allows the first and second conversion keys to be updated more efficiently when either the first or second conversion key is updated than when both the first registration information and the second registration information are updated simultaneously. One example of a method for simultaneously updating both the first registration information and the second registration information is to update the second registration information by converting the first registration information generated in step S165 with the second key in the first key update process without executing the process for updating the second conversion key (step S164). The first key update process described above can reduce the amount of data to be processed compared to this method, thereby allowing the first conversion key to be updated more efficiently.

[0291] Furthermore, according to the first key update process and the second key update process of this embodiment, the update process becomes easier, and in the unlikely event that either the first conversion key or the second conversion key is leaked, a quick response can be made, thereby improving security.

[0292] (Operations and Effects) As described above, according to this embodiment, the information processing system 200 further includes the first collation unit 238 and the second collation unit 253. The first collation unit 238 performs a first collation process using the first converted information. The second collation unit 253 performs a second collation process using the second converted information.

[0293] This allows for matching using the first converted information and the second converted information obtained in sequence from one biometric feature. Because the second converted information is generated through a two-stage conversion process, personal information can be protected more safely than converted information that has undergone only a single stage of conversion process, making it difficult to identify pre-conversion information, etc. Therefore, biometric information can be protected efficiently and safely.

[0294] According to this embodiment, the information processing system 200 includes a first key storage unit 211 that stores a first key and a second key storage unit 231 that stores a second key. The first conversion process is a process of converting biometric information using the pre-stored first key. The second conversion process is a process of converting first converted information using the pre-stored second key.

[0295] This allows the first key used in the first conversion process and the second key used in the second conversion process to be stored separately in different devices, thereby making it possible to safely protect biometric information.

[0296] According to this embodiment, when updating one of the first key and the second key, only one of the first registration information and the second registration information that have been converted and registered in advance using the first key and the second key, respectively, is updated.

[0297] This allows the reconstitution key to be updated efficiently as described above, and also improves security, making it possible to protect biometric information efficiently and safely.

[0298] (Modification 1) In the second embodiment, an example has been described in which the similarity is an inner product. However, the similarity is not limited to an inner product. Furthermore, the evaluation value is not limited to the similarity. The evaluation value and the similarity may be changed as appropriate.

[0299] For example, the similarity may be the cosine similarity, Euclidean distance, Hamming distance, etc. between the registration information vector and the matching information vector. Regarding the cosine similarity, Euclidean distance, and Hamming distance, two vectors x=(x １ , x ２ , ..., x Ｎ ) Ｔ and y = (y １ , y ２ , ..., y Ｎ ) Ｔ Here, the subscript i is an integer from 1 to N.

[0300] (About cosine similarity) Cosine similarity is SUM x ｉ ・y ｉ / (SUM x ｉ ２ ・SUMy ｉ ２ ) １／２ It is defined as follows. A larger cosine similarity indicates a similarity, and a smaller cosine similarity indicates a dissimilarity. As can be seen from this formula, when two vectors x and y are normalized to a magnitude of 1, the normalized correlation is the dot product itself. Therefore, for example, if the registration information vector and the matching information vector are normalized, the normalized correlation can be calculated in the same way as the dot product described above. Note that "SUM" is used as a symbol representing a sum, and corresponds to the Greek capital letter sigma in general mathematical formulas. For example, SUM(pj) represents the sum of p1 to pn, where j is 1 to n. The meaning of "SUM" will be the same hereinafter.

[0301] (About Euclidean distance) Euclidean distance is (SUM(x ｉ -y ｉ ) ２ ) １／２ = (SUM x ｉ ２ +SUMy ｉ ２+SUM(-2x ｉ ・y ｉ )) １／２ To simplify the calculation, we use the SUM(x) without the 1 / 2 power. ｉ -y ｉ ) ２ (also called squared Euclidean distance, etc.) may be used as the similarity measure. The smaller the Euclidean distance and squared Euclidean distance, the more similar they are, and the larger the distance, the more dissimilar they are. As can be seen from this formula, when two vectors x and y are respectively expressed as x' = (SUMx １ ２ , 1, x ２ , ..., x Ｎ ) Ｔ and y' = (1, SUM y ｉ ２ , -2y １ , -2y ２ , ..., -2y Ｎ ) Ｔ Therefore, for example, by converting the registration information vector and the matching information vector as described above, the squared Euclidean distance can be calculated in the same way as the above-described inner product.

[0302] (About Hamming distance) Hamming distance is SUM|x ｉ -y ｉ |=SUMy ｉ +SUMx ｉ (1-2y ｉ ) The smaller the Hamming distance, the more similar the vectors are, and the larger the Hamming distance, the more dissimilar they are. The Hamming distance is often used as an index of similarity between binary vectors (i.e., vectors whose components are either 0 or 1). Two vectors x and y are defined as x' = (1, x １ , x ２ , ..., x ｎ ) Ｔ and y'=(SUMy ｉ , 1-2y １ , 1-2y ２ , ..., 1-2y ｎ ) ＴTherefore, for example, by converting the registration information vector and the matching information vector as described above, the squared Euclidean distance can be calculated in the same way as the above-mentioned inner product.

[0303] This modification also provides the same effects as those of the second embodiment.

[0304] (Variation 2) In the second embodiment, an example has been described in which the information processing system 200 includes the first key generation device 201 a and the second key generation device 201 b. However, the information processing system may include a key generation device that has both the functions of the first key generation device 201 a and the second key generation device 201 b.

[0305] This modification also provides the same effects as those of the second embodiment.

[0306] (Variation 3) In the second embodiment, an example has been described in which the information processing system 200 includes the first update key generation device 270 a and the second update key generation device 270 b. However, the information processing system may include an update key generation device that has both the functions of the first update key generation device 270 a and the second update key generation device 270 b.

[0307] This modification also provides the same effects as those of the second embodiment.

[0308] Third Embodiment In this embodiment, an example in which there are a plurality of first devices and a plurality of second devices will be described. In this embodiment, for the sake of simplicity, descriptions that overlap with those in the second embodiment will be omitted as appropriate.

[0309] 22 is a diagram showing an example of the configuration of an information processing system 300 according to the third embodiment. The information processing system 300 includes two sets of first devices 210a and 210b and second devices 230a and 230b. Except for this point, the information processing system 300 may be configured similarly to the information processing system 200 according to the second embodiment.

[0310] Each of the first devices 210a and 210b may be configured similarly to the first device 210 according to the second embodiment. Each of the second devices 230a and 230b may be configured similarly to the second device 230 according to the second embodiment.

[0311] The second devices 230a and 230b are associated with the first devices 210a and 210b, respectively. The second devices 230a and 230b perform a first verification process using the first converted information generated by the associated first devices 230a and 230b.

[0312] The first key generation device 201a generates a different first key for each of the second devices 230a and 230b, and therefore, for each combination of the second devices 230a and 230b and the associated first devices 210a and 210b, matching can be performed using the first converted information converted using the different first keys.

[0313] 22 shows an example in which there are two second devices 230a and 230b, but the information processing system may include three or more second devices 230. Each second device may be associated with at least one first device 210. One or more first devices 210 associated with some or all of the multiple second devices 230 may overlap with one another in part or in whole.

[0314] When the information processing system includes multiple second devices 230a, 230b, different first keys may be generated for some or all of the multiple second devices 230a, 230b. For example, when common second registration information is used for the multiple different first keys, the multiple first conversion keys and the multiple second conversion keys included in the multiple first keys may be generated so that the composite transformation between each of the multiple first conversion keys and the second conversion key is the same. In detail, for example, one of the multiple first conversion keys and the second conversion key may be generated using processes similar to the first key generation process and the second key generation process according to the second embodiment. Then, the other first conversion keys may be generated using random numbers so that the composite transformation between the first conversion key and the second conversion key previously generated is the same as the composite transformation between the other first conversion key and the previously generated second conversion key.

[0315] (Operations and Effects) According to this embodiment, there are multiple second devices 230a, 230b, and each second device 230a, 230b is associated with at least one first device 210a, 210b. Each second device 230a, 230b performs a first verification process using first converted information generated by the associated at least one first device 210a, 210b. The first key is different for each second device 230a, 230b.

[0316] This allows the second verification process performed using one second key to be associated with the first verification process performed using multiple first keys, making it possible to protect biometric information efficiently and safely when the purpose of verification in the third device 250 is related to the purpose of verification in each of the multiple second devices 230 a, 230 b.

[0317] An example of a case where the third device 250 and multiple second devices 230a, 230b are related for the purpose of matching is when the third device 250 collects and manages multiple databases managed by each of the multiple second devices 230a, 230b.

[0318] Fourth Embodiment In a fourth embodiment, an example will be described in which a "third transformation process" is performed on first transformed information in addition to a "second transformation process." In this embodiment, a detailed example will be described in which "permutation" is used for each of the "first transformation process" and the "second transformation process," and "Lifted-Elgamal encryption" is used for the "third transformation process." However, the types of transformation processes applied to the first transformation process, the second transformation process, and the second transformation process are not limited to these.

[0319] For example, the second embodiment may be modified so that the "second conversion process" applies a conversion used in a secret biometric authentication technology such as "Lifted-Elgamal encryption." In this modification, when updating the first key used in the first conversion process, it may be necessary to update the second registration information, and it may also be necessary to change the processing result of the second conversion process using the second key. In this way, when updating one of the first key and the second key, if it is necessary to change the processing result of the conversion process using the other of the first key and the second key, the amount of processing required to update one of the first key and the second key may be greater than when no change to the processing result is required.

[0320] In this embodiment, an example will be described in which the first converted information is subjected to a "second conversion process" using a second conversion key and a "third conversion process" using a third conversion key. This allows the first key to be updated without updating the second registered information, and the third key to be updated without updating the first registered information.

[0321] In a detailed example according to this embodiment, the "conversion key" in the "component conversion" is used as the "first conversion key." In this detailed example, the "conversion key" in the "component conversion" is used as the "second conversion key." In this detailed example, the "conversion key" in the "Lifted-Elgamal encryption" is used as the "third conversion key."

[0322] In this embodiment, for the sake of simplicity, descriptions that overlap with those in the second embodiment will be omitted as appropriate.

[0323] (Example of Functional Configuration of Information Processing System 400 According to Fourth Embodiment) FIG. 23 is a diagram showing an example of the configuration of an information processing system 400 according to the fourth embodiment.

[0324] The information processing system 400 is a system that sequentially performs a first conversion process, a second conversion process, and a third conversion process on biometric information to generate first converted information and second converted information, and performs matching using each of the first converted information and the second converted information.

[0325] The information processing system 400 includes, for example, a first key generation device 201a, a second key generation device 401b, a first device 210, a second device 430, a third device 450, a first update key generation device 270a, a second update key generation device 470b, and a decryption device 490.

[0326] The same reference numerals are used to designate components having substantially the same functions as those in the second embodiment, and the same applies hereinafter.

[0327] (Example of Functional Configuration of Second Key Generation Device 401b According to Fourth Embodiment) FIG. 24 is a diagram showing an example of the functional configuration of a second key generation device 401b according to the fourth embodiment.

[0328] The second key generation device 401b is an information processing device that generates a second conversion key, a third conversion key, and a third decryption key. The second conversion key in the detailed example according to this embodiment is the "conversion key T" in "component permutation." The third conversion key in the detailed example according to this embodiment is the "conversion key PK" used in "Lifted-Elgamal encryption." The third decryption key in the detailed example according to this embodiment is the "decryption key SK" used in "Lifted-Elgamal encryption." The "third conversion key" and the "third decryption key" are collectively referred to as the "third key." The second key generation device 401b functionally includes, for example, a second key generation unit 404b, a second key transmission unit 405b, and a third key generation unit 405c. The processing performed by these functional components will be described later in the operation section.

[0329] (Example of Functional Configuration of Second Device 430 According to Fourth Embodiment) FIG. 25 is a diagram illustrating an example of the functional configuration of the second device 430 according to the fourth embodiment.

[0330] The second device 430 is an information processing device that stores the second conversion key and the third conversion key, and converts the first converted information using both the second conversion key and the third conversion key to generate second converted information. The second device 430 also performs a matching process (first matching process) using the first converted information.

[0331] The second device 430 functionally includes, for example, a second key storage unit 431, a second key acquisition unit 432, a first registration information storage unit 235, a first converted information acquisition unit 236, a second conversion unit 437, a first comparison unit 238, a first update key transfer unit 241, a first registration information update unit 243, and a second key update unit 445. The second device 430 further functionally includes, for example, a third key storage unit 447, a third conversion unit 448, and a third update unit 449.

[0332] The second converted information includes at least one of second registration information used as registration information and second verification information used as verification information. The second registration information is obtained by sequentially performing the second conversion process and the third conversion process using the second conversion key and the third conversion key, respectively, on the first converted information. The second verification information is obtained by performing the second conversion process using the second conversion key on the first converted information.

[0333] The second key storage unit 431 is a storage unit for storing the second conversion key.

[0334] The third key storage unit 447 is a storage unit for storing the third conversion key.

[0335] The processing performed by the other functional components will be described later in the section on operation.

[0336] (Example of Functional Configuration of Third Device 450 According to Fourth Embodiment) FIG. 26 is a diagram showing an example of the functional configuration of the third device 450 according to the fourth embodiment.

[0337] The third device 450 is an information processing device that performs a matching process (second matching process) using the second converted information.

[0338] The third device 450 functionally includes, for example, a second registration information storage unit 251, a second converted information acquisition unit 452, a second collation unit 453, a second update key transfer unit 254, and a second registration information update unit 255. Furthermore, the third device 450 functionally further includes, for example, a third conversion key storage unit 456, a third conversion key acquisition unit 457, and a third conversion key update unit 458.

[0339] The second registration information storage unit 251 is the same as in the second embodiment. The third conversion key storage unit 456 is a storage unit for storing the third conversion key. The processes performed by the other functional components will be described later in the operation section.

[0340] (Example of Functional Configuration of Second Update Key Generation Device 470b According to Fourth Embodiment) FIG. 27 is a diagram showing an example of the functional configuration of a second update key generation device 470b according to the fourth embodiment.

[0341] The second update key generation device 470b is an information processing device that generates a third update key that is a common update key for updating the third conversion key and the third decryption key. In the detailed example according to this embodiment, the third update key is the "update key Δ" in the "Lifted-Elgamal encryption."

[0342] The second update key generation device 470b functionally includes, for example, a second update key generation unit 474b and a second update key transmission unit 475b. The processes performed by these functional components will be described later in the operation section.

[0343] (Example of Functional Configuration of Decoding Device 490 According to Fourth Embodiment) FIG. 28 is a diagram showing an example of the functional configuration of a decoding device 490 according to the fourth embodiment.

[0344] The decryption device 490 is a device that decrypts the matching result of the second matching process using the third decryption key. That is, in the second matching process according to this embodiment, an encrypted matching result is generated, and the decryption device 490 decrypts this encrypted result.

[0345] The decryption device 490 functionally includes, for example, a decryption key storage unit 491 , a decryption key acquisition unit 492 , a decryption unit 493 , and a decryption key update unit 494 .

[0346] The decryption key storage unit 491 is a storage unit for storing the third decryption key.

[0347] The processing performed by the other functional components will be described later in the section on operation.

[0348] (Example of operation of the information processing system 400 according to the fourth embodiment) The information processing system 400 according to the fourth embodiment executes information processing including a first key generation process, a second key generation process, a registration process, a matching process, a first key update process, and a second key update process. The first key generation process may be the same as that in the second embodiment.

[0349] (Example of Second Key Generation Processing According to Embodiment 4) Fig. 29 is a diagram showing an example of the flow of second key generation processing according to embodiment 4. The second key generation processing is processing for generating and storing a second conversion key, a third conversion key, and a third decryption key.

[0350] The second key generation unit 404b and the third key generation unit 405c generate a second conversion key and a third key using, for example, random numbers (step S401).

[0351] As described above, the second conversion key in the detailed example according to this embodiment is the "conversion key" in "component permutation." Therefore, the second registration key in the detailed example according to this embodiment is the conversion key T that is common to the second registration key and the second matching key. In other words, the conversion key T in the detailed example according to this embodiment functions as the second registration key when used to generate registration information, and functions as the second matching key when used to generate matching information.

[0352] As described above, the third key in the detailed example according to this embodiment includes a third conversion key and a third decryption key. The third conversion key in the detailed example according to this embodiment is the "conversion key PK" used in the "Lifted-Elgamal encryption." The third decryption key in the detailed example according to this embodiment is the "decryption key SK" used in the "Lifted-Elgamal encryption."

[0353] For example, the second key generation unit 404b generates a second conversion key T that represents a method of switching components of a biometric information vector using random numbers and a predetermined rule. The third key generation unit 405c generates a third conversion key PK and a third decryption key SK, which are the public key and private key of the Lifted-Elgamal encryption, using random numbers and a predetermined rule. The second key generation unit 404b and the third key generation unit 405c may, for example, cooperate with each other to generate the second conversion key T, the third conversion key PK, and the third decryption key SK at approximately the same time.

[0354] The random numbers are, for example, true random numbers or pseudo-random numbers generated by a random number generator. The random number generator may be configured using either hardware or a software program.

[0355] The second key transmitting unit 405b transmits the second conversion key and the third conversion key generated in step S401 to the second device 430 (step S402).

[0356] The second key acquisition unit 432 acquires the second conversion key and the third conversion key transmitted in step S402 (step S403).

[0357] The second key acquisition unit 432 stores the second conversion key and the third conversion key acquired in step S403 in the second key storage unit 431 (step S404).

[0358] The second key sending unit 405b sends the third conversion key generated in step S401 to the third device 450 (step S405).

[0359] The third conversion key acquisition unit 457 acquires the third conversion key transmitted in step S405 (step S406).

[0360] The third conversion key acquisition unit 457 stores the third conversion key acquired in step S406 in the third conversion key storage unit 456 (step S407).

[0361] The second key transmitting unit 405b transmits the third decryption key generated in step S401 to the decryption device 490 (step S408).

[0362] The decryption key acquisition unit 492 acquires the third decryption key transmitted in step S408 (step S409).

[0363] The decryption key acquisition unit 492 stores the third decryption key acquired in step S409 in the decryption key storage unit 491 (step S410), and ends the second key generation process. This allows the second conversion key, the third conversion key, and the third decryption key to be generated in advance and stored.

[0364] In the above steps S402, S405, and S408, it is desirable that the key generated in step S401 be transmitted directly only to the second device 430, the third device 450, and the decryption device 490, which use the key, respectively. This reduces the possibility of the key being leaked, and improves security, compared to transmitting the key to a device that uses the key via a device other than the device.

[0365] (Example of Registration Processing According to Embodiment 4) Fig. 30 is a diagram showing an example of the flow of registration processing according to embodiment 4. The registration processing is processing for registering first registration information and second registration information in advance.

[0366] When steps S120 to S124 are executed, the second conversion unit 437 uses the second conversion key stored in the second key memory unit 431 to perform a second conversion process on the first registration information acquired in step S123 to generate second converted information (step S425a).

[0367] For example, the second conversion unit 237 performs permutation on the first registration information using the second conversion key T to generate second converted information.

[0368] The third conversion unit 448 performs a third conversion process on the second converted information generated in step S425a using the third conversion key to generate third converted information (step S425b).

[0369] For example, the third conversion unit 448 performs a third conversion process on (encrypts) the second converted information using the third conversion key PK to generate the third converted information. The third converted information according to this embodiment corresponds to the second registration information.

[0370] Steps S126 to S128 are executed, and the registration process ends.

[0371] This allows the first registration information and the second registration information to be registered using one piece of biometric information.

[0372] 31 and 32 are diagrams showing an example of the flow of the matching process according to embodiment 4. The matching process is a process for performing matching using each of the first matching information and the second matching information.

[0373] After steps S140 to S144 are executed, the second conversion unit 437 uses the second conversion key stored in the second key memory unit 431 to perform a second conversion process on the first matching information acquired in step S143 to generate second matching information (step S445).

[0374] For example, the second conversion unit 437 performs permutation on the first matching information using the second conversion key T to generate second matching information.

[0375] The second conversion unit 437 transmits the second matching information generated in step S445 (step S446).

[0376] For example, the second conversion unit 437 transmits the second matching information to the third device 450 .

[0377] The second converted information acquisition unit 452 acquires the second matching information transmitted in step S446 (step S447).

[0378] The second verification unit 453 performs a second verification process using the second registration information registered in advance and the second verification information acquired in step S447 (step S448).

[0379] As described in "(Example of a Private Biometric Authentication Technology)" and subsequent sections in embodiment 1, additive homomorphic encryption makes it possible to generate an encrypted calculation result by performing a calculation on the encrypted second registration information. Therefore, by performing a calculation on the encrypted second registration information with the second matching information, an encrypted evaluation value can be obtained.

[0380] The evaluation value according to this embodiment is, for example, an inner product. In this case, the matching result of the second matching process according to this embodiment (second matching result) is equivalent to information obtained by encrypting the inner product of the second registration information before encryption and the second matching information (ciphertext of the inner product).

[0381] In this embodiment, an example has been described in which the third device 450 executes the second matching process (step S448), but the method for obtaining the second matching result is not limited to this. The second device 430 and the third device 450 may communicate with each other, and one of the devices 430 or 450 may generate the second matching result using the second matching information and the second registration information. For example, the second device 430 may obtain the second registration information from the third device 450 and perform the matching process with the second matching information (second matching process). According to this example, only encrypted biometric information needs to be transmitted and received between the second device 430 and the third device 450, thereby improving security.

[0382] See Fig. 32. The second collation unit 453 transmits the second collation result generated in step S448 (step S449).

[0383] For example, the second matching unit 453 transmits the second matching information to the decryption device 490 .

[0384] Upon receiving the second matching result transmitted in step S449, the decryption unit 493 decrypts the received second matching result (step S450).

[0385] For example, the decryption unit 493 acquires the decryption result by decrypting the second matching result using the third decryption key stored in the decryption key storage unit 491. The decryption result according to this embodiment is information indicating the dot product of the second registration information before encryption and the second matching information (plaintext of the dot product).

[0386] The decoding unit 493 transmits the decoding result obtained in step S450 (step S451).

[0387] For example, the decryption unit 493 transmits the decryption result to the third device 450 .

[0388] The second collation unit 453 acquires the decryption result generated in step S451 (step S452), and ends the collation process.

[0389] This allows the third device 450 to perform authentication etc. using the decryption result. Note that the decryption result may be transmitted to another device (not shown) and used for authentication etc. in the other device.

[0390] (Example of First Key Update Processing According to Fourth Embodiment) FIG. 33 is a diagram showing an example of the flow of first key update processing according to the fourth embodiment.

[0391] The first key update process is a process for updating the first conversion key.

[0392] After steps S161 to S163 are executed, step S464, which replaces step S164 in the second embodiment, is executed.

[0393] The second key update unit 445 updates the current second conversion key using the first update key acquired in step S163 (step S464).

[0394] For example, the second key update unit 445 updates the first update key S Δ and the second conversion key T stored in the second key storage unit 431 to obtain a new second conversion key T. The second key update unit 445 stores the obtained new second conversion key T in the second key storage unit 431. As a result, the current second conversion key T is updated to the new second conversion key T.

[0395] Subsequently, steps S165 to S167 are executed, and the first key update process ends.

[0396] By performing such a first key update process, it is possible to update the first conversion key without changing the second registration information and the third key stored in the third device 450. Therefore, it is possible to efficiently update the first conversion key without communicating with the third device 450.

[0397] (Example of Second Key Update Processing According to Fourth Embodiment) FIG. 34 is a diagram showing an example of the flow of second key update processing according to the fourth embodiment.

[0398] The second key update process is a process for updating the third conversion key PK and the third decryption key SK.

[0399] In the second key update process according to this embodiment, steps S471 to S476 are executed, which are generally equivalent to steps S171 to S176 according to the second embodiment. Δ , M Δ －１The update key Δ is used instead of the current conversion keys M and M in the second embodiment. －１ In the second embodiment, the decryption key SK is used instead of the update key M Δ , M Δ －１ The destination of the update key Δ is the second device 230 , but in this embodiment, the destination of the update key Δ is the decryption device 490 .

[0400] Furthermore, in the second key update process according to this embodiment, the second device 430 and the third device 450 execute steps S481 to S483 between steps S474 and S475.

[0401] The second key update process according to this embodiment will be described below.

[0402] The second update key generating unit 474b generates a third update key using, for example, a random number (step S471).

[0403] For example, the second update key generation unit 474b generates the update key Δ using a random number, similar to the second update key generation unit 274b.

[0404] The second update key transmitting unit 475b transmits the third update key generated in step S471 (step S472).

[0405] For example, the second update key transmission unit 475 b transmits the third update key to the third device 450 .

[0406] The second update key transfer unit 254 acquires the third update key transmitted in step S472 (step S473).

[0407] As in step S174, the second registration information update unit 255 updates the second registration information stored in the second registration information storage unit 251 using the third update key acquired in step S473 (step S474).

[0408] For example, the second registration information update unit 255 converts the current second registration information using the third update key Δ to calculate new second registration information. The second registration information update unit 255 stores the new second registration information in the second registration information storage unit 251. As a result, the second registration information update unit 255 updates the second registration information using the third update key.

[0409] The third conversion key update unit 458 uses the third update key obtained in step S473 to update the current third conversion key (i.e., the third conversion key stored in the third conversion key memory unit 456) (step S481).

[0410] For example, the third conversion key update unit 458 generates a new third conversion key PK using the third update key Δ and the current third conversion key PK. ｎｅｗ The third conversion key update unit 458 calculates the new third conversion key PK ｎｅｗ in the third conversion key storage unit 456. As a result, the third conversion key PK stored in the third conversion key storage unit 456 is updated.

[0411] The third conversion key update unit 458 transmits the third conversion key acquired in step S481 (i.e., the new third conversion key) (step S482).

[0412] For example, the third conversion key update unit 458 generates a new third conversion key PK ｎｅｗ to the second device 430.

[0413] When the third update unit 449 acquires the third conversion key transmitted in step S482, it uses the acquired third conversion key to update the third conversion key stored in the third key memory unit 447 (step S483).

[0414] For example, the third update unit 449 updates the third conversion key PK stored in the third key storage unit 447 with the acquired third conversion key PK ｎｅｗ By replacing it with the above, the third conversion key PK stored in the third key storage unit 447 is updated.

[0415] The second update key transfer unit 254 transmits the third update key acquired in step S473 (step S475).

[0416] For example, the second update key transfer unit 254 transmits the third update key Δ to the decryption device 490 .

[0417] When the decryption key update unit 494 acquires the third update key transmitted in step S475, it uses the acquired third update key to update the decryption key stored in the decryption key memory unit 491 (step S476), and terminates the second key update process.

[0418] For example, the decryption key update unit 494 updates the current decryption key SK with the third update key Δ to generate a new decryption key SK ｎｅｗ The decryption key update unit 494 calculates the new decryption key SK ｎｅｗ In this way, the decryption key update unit 494 stores the decryption key SK ｎｅｗ Update the current decryption key SK using

[0419] By performing such second key update processing, it is possible to update only the third conversion key and the second registration information, independently of the first registration information and the first and second conversion keys.

[0420] By executing the first key update process and the second key update process, the first and second conversion keys and the third conversion keys and the third decryption keys can be updated independently of each other. Therefore, the first key update process and the second key update process may be executed at the same time or at different times.

[0421] This allows the re-key to be updated efficiently as described in the second embodiment, and also improves security.

[0422] (Operations and Effects) As described above, according to this embodiment, the information processing system 400 further includes the third conversion unit 448 that performs the third conversion process on the second converted information using the third key to generate the third converted information. The first conversion process and the third conversion process are performed by different devices 210 and 430.

[0423] Since the first conversion process and the third conversion process are performed in different devices, the first key and the third key can be stored separately in different devices, thereby making it possible to safely protect biometric information.

[0424] According to this embodiment, the third key is commonly used for biometric information of different individuals.

[0425] This allows biometric information to be protected safely without the need for an individual to perform operations such as inputting a password each time verification is performed, thereby enabling biometric information to be protected efficiently and safely.

[0426] According to this embodiment, the first key and the third key are updated independently of each other.

[0427] This allows the reconstitution key to be updated efficiently as described above, and also improves security, making it possible to protect biometric information efficiently and safely.

[0428] According to this embodiment, the first conversion process and the third conversion process are different types of conversion processes. The first key and the third key are different keys used to convert biometric information. The third key includes a public key (conversion key PK) and a private key (decryption key SK).

[0429] This allows for more secure protection of personal information by applying a protection technique using a public key and a private key, and therefore makes it possible to securely protect biometric information.

[0430] Although the embodiments and modifications have been described above with reference to the drawings, these are merely examples of this disclosure, and various configurations other than those described above can also be adopted.

[0431] In addition, although the flowcharts used in the above description show multiple steps (processes) in a sequential order, the order of steps performed in each embodiment is not limited to the order shown. In each embodiment, the order of steps shown in the drawings can be changed as long as it does not cause any problems in terms of content. Furthermore, the above-described embodiments and variations can be combined as long as the content is not contradictory.

[0432] Some or all of the above-described embodiments can be described as, but are not limited to, the following supplementary notes.

[0433] 1. An information processing system comprising: first conversion means that performs a first conversion process on biometric information using a first key to generate first converted information; and second conversion means that performs a second conversion process on the first converted information using a second key to generate second converted information, wherein the first conversion process and the second conversion process are performed by different devices. 2. The information processing system described in 1., wherein the first conversion process and the second conversion process include different types of conversion processes. 3. The information processing system described in 1. or 2., further comprising: first verification means that performs a first verification process using the first converted information; and second verification means that performs a second verification process using the second converted information. 4. The information processing system described in any one of 1. to 3., wherein the first key and the second key are used in common for the biometric information of different individuals. 5. The information processing system according to any one of 1. to 4., comprising: first key storage means for storing the first key; and second key storage means for storing the second key; wherein the first conversion process is a process of converting the biometric information using the first key stored in advance; and the second conversion process is a process of converting the first converted information using the second key stored in advance. 6. The information processing system according to any one of 1. to 5., wherein when one of the first key and the second key is updated, with regard to first registered information and second registered information converted using the first key and the second key, respectively, and registered in advance, only one of the registered information is updated. 7. The information processing system according to any one of 1. to 6., further comprising third conversion means for performing a third conversion process on the second converted information using a third key to generate third converted information, wherein the first conversion process and the third conversion process are performed by different devices. 8. The third key is used in common for the biometric information of different individuals. 7. 9. The information processing system described in 7. or 8., in which the first key and the third key are updated independently of each other. 10. The information processing system described in any one of 7. to 9., in which the first conversion process and the third conversion process are different types of conversion processes, the first key and the third key are different keys used to convert the biometric information, and the third key includes a public key and a private key.11. The information processing system described in any one of 1. to 10., wherein there are multiple second devices equipped with the second conversion means, each associated with at least one first device equipped with the first conversion means, and each of the second devices performs a first verification process using the first converted information generated by the associated at least one first device, and the first key is different for each second device. 12. An information processing device comprising: first converted information acquisition means for acquiring, via a network, first converted information obtained by performing a first conversion process on biometric information; and second conversion means for performing a second conversion process on the first converted information to generate second converted information. 13. The information processing device described in 12., wherein the first conversion process and the second conversion process include different types of conversion processes. 14. The information processing device described in 12. or 13., further comprising: first verification means for performing a first verification process using the first converted information; and second verification means for performing a second verification process using the second converted information. 15. The information processing device according to any one of 12. to 14., wherein the first key and the second key are commonly used for the biometric information of different individuals. 16. The information processing device according to any one of 12. to 15., comprising: a first key storage means for storing the first key; and a second key storage means for storing the second key, wherein the first conversion process is a process of converting the biometric information using the first key stored in advance; and the second conversion process is a process of converting the first converted information using the second key stored in advance. 17. The information processing device according to any one of 12. to 16., wherein, when one of the first key and the second key is updated, with regard to first registration information and second registration information that have been converted using the first key and the second key, respectively, and registered in advance, only one of the registration information is updated. 18. The information processing device according to any one of 12. to 17., further comprising third conversion means for performing a third conversion process on the second converted information using a third key to generate third converted information, wherein the first conversion process and the third conversion process are performed by different devices. 19. The information processing device according to 18., wherein the third key is used in common for the biometric information of different individuals.20. The information processing device according to 18. or 19., in which the first key and the third key are updated independently of each other. 21. The information processing device according to any one of 18. to 20., in which the first conversion process and the third conversion process are different types of conversion processes, the first key and the third key are different keys used to convert the biometric information, and the third key includes a public key and a private key. 22. The information processing device according to any one of 12. to 21., in which at least one first device is associated with the information processing device, generating the first converted information by performing the first conversion process on the biometric information, and a first verification process is performed using the first converted information generated by the associated at least one first device. 23. An information processing method, in which a first device performs a first conversion process on biometric information using a first key to generate first converted information, and a second device different from the first device performs a second conversion process on the first converted information using a second key to generate second converted information. 24. The information processing method according to 23., wherein the first conversion process and the second conversion process include different types of conversion processes. 25. The information processing method according to 23. or 24., further comprising performing a first matching process using the first converted information, and performing a second matching process using the second converted information. 26. The information processing method according to any one of 23. to 25., wherein the first key and the second key are used in common for the biometric information of different individuals. 27. The information processing method according to any one of 23. to 26., wherein the first conversion process is a process of converting the biometric information using the first key stored in advance, and the second conversion process is a process of converting the first converted information using the second key stored in advance. 28. When updating one of the first key and the second key, with regard to first registration information and second registration information converted using the first key and the second key, respectively, and registered in advance, only one of the registration information is updated. 10. The information processing method according to claim 9, wherein:29. The information processing method according to any one of 23. to 28., further comprising generating third converted information by performing a third conversion process on the second converted information using a third key, wherein the first conversion process and the third conversion process are performed by different devices. 30. The information processing method according to 29., wherein the third key is used in common for the biometric information of different individuals. 31. The information processing method according to 29. or 30., wherein the first key and the third key are updated independently of each other. 32. The information processing method according to any one of 29. to 31., wherein the first conversion process and the third conversion process are different types of conversion processes, the first key and the third key are different keys used to convert the biometric information, and the third key includes a public key and a private key. 33. The information processing method described in any one of 23. to 32., wherein there are multiple second devices, each associated with at least one of the first devices, and each of the second devices performs a first verification process using the first converted information generated by the associated at least one first device, and the first key is different for each of the second devices. 34. A program for causing a first device to perform a first conversion process on biometric information using a first key to generate first converted information, and causing a second device different from the first device to perform a second conversion process on the first converted information using a second key to generate second converted information. 35. The program described in 34., wherein the first conversion process and the second conversion process include different types of conversion processes. 36. The program described in 34. or 35., further including performing a first verification process using the first converted information, and performing a second verification process using the second converted information. 37. The program described in any one of 34. to 36., wherein the first key and the second key are commonly used for the biometric information of different individuals. 38. The program described in any one of 34. to 37., wherein the first conversion process is a process of converting the biometric information using the first key that is stored in advance, and the second conversion process is a process of converting the first converted information using the second key that is stored in advance.39. The program described in any one of 34. to 38., wherein, when updating one of the first key and the second key, with regard to first registration information and second registration information that have been converted using the first key and the second key, respectively, and registered in advance, only one of the registration information is updated. 40. The program described in any one of 34. to 39., further comprising: generating third converted information by performing a third conversion process on the second converted information using a third key, wherein the first conversion process and the third conversion process are performed by different devices. 41. The information processing method described in 40., wherein the third key is used in common for the biometric information of different individuals. 42. The program described in 40. or 41., wherein the first key and the third key are updated independently of each other. 43. The program described in any one of 40. to 42., wherein the first conversion process and the third conversion process are different types of conversion processes, the first key and the third key are mutually different keys used to convert the biometric information, and the third key includes a public key and a private key. 44. The program described in any one of 34. to 43., wherein the second devices are multiple and each is associated with at least one of the first devices, and each of the second devices performs a first verification process using the first converted information generated by the associated at least one first device, and the first key is mutually different for each of the second devices. 45. A recording medium having recorded thereon a program for causing a first device to perform a first conversion process on biometric information using a first key to generate first converted information, and causing a second device different from the first device to perform a second conversion process on the first converted information using a second key to generate second converted information. 46. A recording medium having recorded thereon the program described in 45., wherein the first conversion process and the second conversion process include different types of conversion processes. 47. A recording medium having recorded thereon the program described in 45. or 46., further including performing a first verification process using the first converted information, and performing a second verification process using the second converted information.48. A recording medium having recorded thereon the program described in any one of 45. to 47., wherein the first key and the second key are commonly used for the biometric information of different individuals. 49. A recording medium having recorded thereon the program described in any one of 45. to 48., wherein the first conversion process is a process of converting the biometric information using the first key stored in advance, and the second conversion process is a process of converting the first converted information using the second key stored in advance. 50. A recording medium having recorded thereon the program described in any one of 45. to 49., wherein when one of the first key and the second key is updated, with regard to first registered information and second registered information that have been converted using the first key and the second key, respectively, and that have been registered in advance, only one of the registered information is updated. 51. A recording medium having recorded thereon the program described in 45. to 50., further comprising performing a third conversion process on the second converted information using a third key to generate third converted information, wherein the first conversion process and the third conversion process are performed by different devices. 52. A recording medium having recorded thereon the program described in any one of 51. to 52.. 52. The information processing method described in 51., in which the third key is used in common for the biometric information of different individuals. 53. A recording medium having recorded thereon the program described in 51. or 52., in which the first key and the third key are updated independently of each other. 54. A recording medium having recorded thereon the program described in any one of 51. to 53., in which the first conversion process and the third conversion process are different types of conversion processes, the first key and the third key are different keys used to convert the biometric information, and the third key includes a public key and a private key. 55. A recording medium having recorded thereon the program described in any one of 45. to 54., in which the second devices are multiple and each is associated with at least one of the first devices, each of the second devices performs a first verification process using the first converted information generated by the associated at least one first device, and the first key is different for each of the second devices.

[0434] 100, 200, 300, 400 Information processing system 110, 210, 210a, 210b First device 130, 230, 230a, 230b, 430 Second device 136, 236 First converted information acquisition unit 137 Second conversion unit 250, 450 Third device 201a, 401b First key generation device 201b Second key generation device 204a First key generation unit 204b, 404b Second key generation unit 205a First key transmission unit 205b, 405b Second key transmission unit 211 First key storage unit 212 First key acquisition unit 216 Biometric information acquisition unit 217 First conversion unit 221 First key update unit 231, 431 Second key storage unit 232, 432 Second key acquisition unit 235 First registration information storage unit 237, 437 Second conversion unit 238 First verification unit 241 First update key transfer unit 242 Second key calculation unit 243 First registration information update unit 245, 445 Second key update unit 251 Second registration information storage unit 252, 452 Second converted information acquisition unit 253, 453 Second verification unit 254 Second update key transfer unit 255 Second registration information update unit 270a First update key generation device 270b, 470b Second update key generation device 274a First update key generation unit 274b, 474b Second update key generation unit 275a First update key transmission unit 275b, 475b Second update key transmission unit 405c Third key generation unit 447 Third key storage unit 448 Third conversion unit 449 Third update unit 456 Third conversion key storage unit 457 Third conversion key acquisition unit 458 Third conversion key update unit 490 Decryption device 491 Decryption key storage unit 492 Decryption key acquisition unit 493 Decryption unit 494 Decryption key update unit

Claims

1. An information processing system comprising: a first conversion means for performing a first conversion process on biometric information using a first key to generate first converted information; and a second conversion means for performing a second conversion process on the first converted information using a second key to generate second converted information, wherein the first conversion process and the second conversion process are performed by different devices.

2. The information processing system according to claim 1, wherein the first conversion process and the second conversion process include different types of conversion processes.

3. An information processing system as described in claim 1 or 2, further comprising: a first matching means for performing a first matching process using the first converted information; and a second matching means for performing a second matching process using the second converted information.

4. An information processing system according to any one of claims 1 to 3, wherein the first key and the second key are used in common for the biometric information of different individuals.

5. An information processing system as claimed in any one of claims 1 to 4, comprising a first key storage means for storing the first key, and a second key storage means for storing the second key, wherein the first conversion process is a process for converting the biometric information using the first key that has been stored in advance, and the second conversion process is a process for converting the first converted information using the second key that has been stored in advance.

6. An information processing system according to any one of claims 1 to 5, wherein when one of the first key and the second key is updated, only one of the first registration information and the second registration information that have been converted and registered in advance using the first key and the second key, respectively, is updated.

7. An information processing system as claimed in any one of claims 1 to 6, further comprising a third conversion means for performing a third conversion process on the second converted information using a third key to generate third converted information, wherein the first conversion process and the third conversion process are performed by different devices.

8. The information processing system according to claim 7, wherein the third key is used commonly for the biometric information of different individuals.

9. The information processing system according to claim 7 or 8, wherein the first key and the third key are updated independently of each other.

10. An information processing system as claimed in any one of claims 7 to 9, wherein the first conversion process and the third conversion process are different types of conversion processes, the first key and the third key are different keys used to convert the biometric information, and the third key includes a public key and a private key.

11. An information processing system as claimed in any one of claims 1 to 10, wherein there are multiple second devices each equipped with the second conversion means, each of which is associated with at least one first device equipped with the first conversion means, each of the second devices performs a first matching process using the first converted information generated by the associated at least one first device, and the first key is different for each of the second devices.

12. An information processing device comprising: a first converted information acquisition means for acquiring, via a network, first converted information obtained by performing a first conversion process on biometric information; and a second conversion means for performing a second conversion process on the first converted information to generate second converted information.

13. An information processing method, in which a first device performs a first conversion process on biometric information using a first key to generate first converted information, and a second device different from the first device performs a second conversion process on the first converted information using a second key to generate second converted information.

14. A recording medium having recorded thereon a program for causing a first device to perform a first conversion process on biometric information using a first key to generate first converted information, and for causing a second device different from the first device to perform a second conversion process on the first converted information using a second key to generate second converted information.

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