OWNER IDENTITY CONFIRMATION SYSTEM AND OWNER IDENTITY CONFIRMATION METHOD

Abstract

The owner sameness confirmation system determines whether or not the owners of two terminals (200A, 200B) are the same. Authentication station servers (100A, 100B) store electronic certificates issued to the terminals and identity confirmation information of the owners of the terminals in association with each other. The terminal (200B) transmits information obtained by encrypting the identity confirmation information of the owner of the terminal (200B) through homomorphic encryption and the electronic certificate of the partner terminal (200A) to the authentication station server (100A). The authentication station server (100A) transmits response encrypted information including information obtained by encrypting the identity confirmation information of the owner of the terminal (200A) as a response. The terminal (200B) decrypts the response encrypted information and determines the sameness of the owners based on whether or not the decryption result matches a predetermined value.

Description

TECHNICAL FIELD

The present invention relates to an owner sameness confirmation system and an owner sameness confirmation method.

BACKGROUND ART

Various services such as product purchasing and administrative procedures have started being provided online. During service provision, user authentication including identity confirmation is essential.

User authentication using public key infrastructure is one example of user authentication. With public key infrastructure, an identity confirmation document (e.g., driver's license, etc.) of a user is checked at an authentication station (a certificate issuance server or authentication station server of an authentication station), and thereafter a public key certificate (electronic certificate) is issued to the terminal owned by the user.

The terminal generates a signature (digital signature) for data using a secret key, and transmits the generated signature to a server (the server that authenticates the user and provides the service to the terminal) together with the electronic certificate. The server confirms that the electronic certificate is authentic by confirming (successfully verifying) the signature of the authentication station given to the electronic certificate. Next, the server verifies the signature given to the data using a public key included in the electronic certificate. If verification is successful, the server can confirm that the data was transmitted from the user. Furthermore, the server can obtain information relating to the user from the information included in the electronic certificate.

When the user is in possession of multiple terminals, it is preferable that data can be shared between the terminals. For example, if one service is used from multiple terminals, it is desirable that the public key used for user authentication during service use is shared between the terminals and the user is authenticated as the same user from any terminal. There are also cases in which the user wishes to share the data needed for copyright management in order to view content on multiple terminals. When data is to be shared, it is a prerequisite that the owners of the terminals are the same, and it needs to be confirmed that the owners are the same before sharing is performed.

The technique disclosed in NPL 1 is a technique for confirming that the owners of multiple terminals are the same. In this technique, an electronic certificate (owner electronic certification) is issued to each terminal. Each of two terminals can confirm that the owner is the same by comparing the electronic certificate of the terminal and the electronic certificate of a partner (partner terminal), and it is possible to share data between terminals or between applications of the terminal (e.g., a content viewing application).

An example of a FIDO client and an authenticator in FIDO (Fast IDentity Online), which is an authentication technique used instead of a password, is another example in which it is required that the owners are the same. Since the FIDO client and the authenticator execute user authentication in a linked manner, it is a prerequisite that the owner is the same. For this reason, confirmation of the fact that the owner of the FIDO client and the owner of the authenticator are the same is required before user authentication.

CITATION LIST

Non Patent Literature

• [NPL 1] Ogata, Y., others, Study Regarding Maintenance and Management of Secret key for Authentication Scheme Using Non-Symmetrical Key, Proceedings of the 2016 IEICE Society Conference, B-7-9, 2016.

SUMMARY OF THE INVENTION

Technical Problem

The method described in NPL 1, in which the sameness of the owners is confirmed by comparing electronic certificates in multiple terminals with the same owner, has two further problems from the perspective of improving usability and improving security. One problem is that the sameness of the owners cannot be confirmed if electronic certificates have been issued from different authentication stations. If the authentication stations are different, the item (type) of the identity confirmation information or the format will be different, whereby it will not be possible to compare in some cases even though the owners are the same. The other problem is that there is a risk that the identity confirmation information included in the electronic certificate will be stolen and misused. If owner sameness confirmation processing is executed with an unauthorized terminal that has been stolen or the like, there is a risk that information relating to the identity confirmation information included in the electronic certificate will leak out and be misused.

The present invention was made in view of this kind of background and aims to enable owner sameness confirmation between terminals while ensuring security.

Means for Solving the Problem

In order to solve the above-described problem, an owner sameness confirmation system is an owner sameness confirmation system constituted by including a plurality of terminals and a plurality of authentication station servers, in which each of the terminals includes: a storage unit configured to store identity confirmation information of an owner of the terminal; and a confirmation request unit configured to transmit a confirmation request message including encrypted information obtained by encrypting the identity confirmation information of the owner of the terminal using a public key for homomorphic encryption, an electronic certificate of a partner terminal that is a target of owner sameness confirmation, and the public key, to an authentication station server that issued the electronic certificate to the partner terminal, the authentication station server that issued the electronic certificate to the partner terminal includes: a storage unit configured to store the electronic certificate issued to the partner terminal and identity confirmation information of an owner of the partner terminal in association with each other; and a confirmation response unit configured to, upon receiving the confirmation request message, acquire the identity confirmation information of the owner of the partner terminal from the electronic certificate of the partner terminal, and transmit a confirmation response message including response encrypted information, which is the result of calculating an encrypted text obtained by encrypting the identity confirmation information using the public key and the encrypted information through computation corresponding to the homomorphic encryption, as a response to the terminal, and each of the terminals further includes: a sameness determination unit configured to decrypt the response encrypted information, and determine whether or not the identity confirmation information of the owner of the terminal and the identity confirmation information of the owner of the partner terminal match each other based on whether or not the decryption result matches a predetermined value.

Effects of the Invention

According to the present invention, it is possible to confirm the sameness of owners between terminals while ensuring security.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing an overall configuration of an owner sameness confirmation system according to the present embodiment.

FIG. 2 is a diagram showing a hardware configuration of a computer according to the present embodiment.

FIG. 3 is a diagram showing a functional configuration of an authentication station server according to the present embodiment.

FIG. 4 is a diagram showing a data configuration of an electronic certificate database according to the present embodiment.

FIG. 5 is a diagram showing a hardware configuration of the computer according to the present embodiment.

FIG. 6 is a diagram showing a functional configuration of a terminal according to the present embodiment.

FIG. 7 is a sequence diagram of processing for issuing an owner electronic certificate according to the present embodiment.

FIG. 8 is a sequence diagram of processing for issuing a one-time electronic certificate according to the present embodiment.

FIG. 9 is a sequence diagram (1) of owner sameness confirmation processing according to the present embodiment.

FIG. 10 is a sequence diagram (2) of owner sameness confirmation processing according to the present embodiment.

FIG. 11 is a sequence diagram (3) of owner sameness confirmation processing according to the present embodiment.

DESCRIPTION OF EMBODIMENTS

Hereinafter, an owner sameness confirmation system for confirming the sameness of an owner of a terminal according to a mode for carrying out the present invention (embodiment) will be described. The owner sameness confirmation system is constituted by including a terminal and an authentication station server for issuing an electronic certificate (also written simply as “certificate”) to the terminal. The authentication station server holds identity confirmation information that was referenced in owner confirmation performed when the electronic certification was issued to the terminal. The terminal also stores the identity confirmation information of the owner of the terminal.

There are two types of electronic certification, namely an owner electronic certification and a one-time electronic certification. First, the identity confirmation information of the user of the terminal is confirmed, and the authentication station server issues an owner electronic certificate to the terminal and stores the owner electronic certificate in association with the identity confirmation information.

When the sameness between the owner of the terminal and the owner of another terminal (partner terminal) is to be confirmed, the terminal requests issuance of the one-time electronic certificate to the authentication station server that issued the owner electronic certificate (the authentication station server of the terminal). The issuance request is signed with a secret key corresponding to the owner electronic certificate. The authentication station server issues the one-time electronic certificate to the terminal and stores the one-time electronic certificate in association with the owner electronic certificate, and consequently, in association with the identity confirmation information.

With the owner sameness confirmation system, the terminal and the authentication station server of the partner terminal determine whether or not the owners of the terminal and the partner terminal are the same. In the determination, the terminal transmits encrypted information obtained by encrypting the identity confirmation information held by the terminal through homomorphic encryption to the authentication station server of the partner terminal via the partner terminal. Upon receiving the encrypted information, the authentication station server of the partner terminal encrypts the identity confirmation information of the partner terminal held by the authentication station server through homomorphic encryption and transmits a response encrypted information obtained by multiplying together the encrypted identity confirmation information and the received encrypted information as a response to the terminal via the partner terminal. The terminal decrypts the received data, and if it matches a predetermined value, the terminal determines that the identity confirmation information held by the terminal and the identity confirmation information of the partner terminal held by the authentication station server of the partner terminal are the same, and determines that the owners of the terminals are the same. Since the identity confirmation information is compared while encrypted through homomorphic encryption, the identity confirmation information does not leak out between the terminal and the authentication station server.

Overall Configuration of Owner Sameness Confirmation System

FIG. 1 is a diagram showing an overall configuration of an owner sameness confirmation system 10 according to the present embodiment. The owner sameness confirmation system 10 is constituted by including multiple authentication station servers 100 and multiple terminals 200. The authentication station servers 100 and the terminals 200 can communicate with each other via a network 900. A server of a route authentication station 300 that issued the electronic certificate to the authentication station server 100 may also be connected to the network 900.

Hardware Configuration of Authentication Station Server FIG. 2 is a diagram showing a hardware configuration of a computer 100Z according to the present embodiment. The computer 100Z is constituted by including a CPU 101, a RAM (Random Access Memory) 102, a ROM (Read Only Memory) 103, an SSD (Solid State Drive) 104, an NIC (Network Interface Card) 105, an input/output interface 106 (written as “input/output I/F (interface)” in FIG. 2), and a media drive 107.

The NIC 105 is connected to the network 900. A display and a user interface apparatus 198 (written as “UI (User Interface) apparatus” in FIG. 2) such as a keyboard and a mouse are connected to the input/output interface 106. The media drive 107 reads a program on a recording medium 199. The recording medium 199 is an optical recording medium such as a DVD (Digital Versatile Disc), a magneto-optical recording medium such as an MO (Magneto Optical disk), a magnetic recording medium, a semiconductor memory, or the like. The computer 100Z functions as the authentication station server 100 that will be described hereinafter, due to the CPU 101 executing the read program (see “authentication station program 121” in FIG. 3, which will be described later).

Functional Configuration of Authentication Station Server

FIG. 3 is a diagram showing a functional configuration of the authentication station server 100 according to the present embodiment. The authentication station server 100 is constituted by including a control unit 110, a storage unit 120, and an input/output unit 150. The input/output unit 150 is constituted by including an NIC 105, an input/output interface 106, and a media drive 107, and performs transmission and reception of communication data with the terminal 200 (see FIG. 1) and another authentication station server 100 (see FIG. 1). Also, the input/output unit 150 loads the authentication station program 121 from the recording medium 199. The storage unit 120 stores the authentication station program 121, an electronic certificate database 130 (see FIG. 4, which will be described later), and data that is needed in order to function as the authentication station server 100, which includes the secret key and the electronic certificate of the authentication station server 100 issued by the route authentication station 300.

Electronic Certificate Database of Authentication Station Server

FIG. 4 is a diagram showing a data configuration of the electronic certificate database 130 according to the present embodiment. The electronic certificate database 130 is, for example, data in a table format. One row (record) of the electronic certificate database 130 indicates one electronic certificate issued by the authentication station server 100, and is constituted by including identification information 131, a type 132, a key owner 133, a related certificate 134, an identity confirmation information 135, and an electronic certificate 136.

The identification information 131 is identification information of the electronic certificate (e.g., a serial number included in the electronic certificate). The type 132 is the type of the electronic certificate. The type 132 includes “owner”, which indicates an owner electronic certificate issued to the terminal 200 after the owner was confirmed, “one-time”, which indicates an electronic certificate issued temporarily to a terminal in order to confirm the sameness of the user, and the like. The key owner 133 is the issuance destination of the electronic certificate and indicates the owner (Subject field of the electronic certificate) of the key pair (secret key and public key). The related certificate 134 is the identification information 131 of a related electronic certificate. A related electronic certificate is, for example, an owner electronic certificate of the terminal that is the issuance destination of the one-time electronic certificate in the one-time electronic certificate.

The identity confirmation information 135 is identity confirmation information that was confirmed when the owner electronic certificate was issued. Information indicated in a residence certificate, a driver's license, or the like is an example of the identity confirmation information, and the identity confirmation information 135 includes data (image data, electronic data) of the identity confirmation information, an address, a name, a driver's license number, or information for accessing the identity confirmation information. The electronic certificate 136 is electronic certificate data issued by the authentication station server 100. Note that in addition to the public key (Subject Public Key Info field of the electronic certificate), the electronic certificate includes a key owner 133 (Subject field), identification information (Issuer field) of the authentication station that performed issuance, a validity period (Validity field), a serial number (Serial Number field), and the like.

The record 138 is a record of the owner certificate whose identification information 131 is “38473857”, the key owner 133 is the name of the owner, and the address of the owner is included as the identity confirmation information 135. The record 139 is a record of the one-time electronic certificate whose identification information 131 is “84736401”, and is related to the electronic certificate indicated in the record 138. Specifically, the electronic certificate of the record 139 is a one-time electronic certificate that was issued to the terminal, which is the issuance destination of the electronic certificate of the record 138. The record 139 of the one-time electronic certificate does not include the identity confirmation information in the identity confirmation information 135, but the authentication station server 100 can acquire the identity confirmation information from the identity confirmation information 135 of the record 138 of the owner electronic certificate indicated in the related certificate 134.

Control Unit of Authentication Station Server Returning to FIG. 3, the description of the control unit 110 will continue. The control unit 110 is constituted by including an electronic certificate issuance unit 111, a confirmation reception unit 112, and a confirmation response unit 113.

The electronic certificate issuance unit 111 issues an electronic certificate in response to a request from the terminal 200 (see FIG. 1). The issued electronic certificate is stored in the electronic certificate database 130.

The confirmation reception unit 112 receives a terminal-issued confirmation request start message (see step S401 in FIG. 10, which will be described later) requesting a random number from the terminal 200, and transmits a random number as a response.

From the terminal 200, the confirmation response unit 113 receives a confirmation request transfer message (see step S411 in FIG. 11, which will be described later) including information of the partner terminal 200 for confirming the sameness of the owners. Also, the confirmation response unit 113 generates response encrypted information by multiplying together data obtained by encrypting the identity confirmation information of the owner stored by the authentication station server 100 of the partner 200 using a public key for homomorphic encryption, and the received encrypted information. The confirmation response unit 113 transmits a confirmation response message (see step S416 in FIG. 11, which will be described later) including the response encrypted information as a response.

Hardware Configuration of Terminal

FIG. 5 is a diagram showing a hardware configuration of a computer 200Z according to the present embodiment. The computer 200Z has a similar configuration to the computer 100Z (see FIG. 2). The media drive 207 reads a program on a recording medium 299. The computer 200Z functions as the terminal 200 that will be described hereinafter, due to the CPU 201 executing the read program (see “terminal program 221” in FIG. 6, which will be described later).

Functional Configuration of Terminal

FIG. 6 is a diagram showing a functional configuration of the terminal 200 according to the present embodiment. The terminal 200 is constituted by including a control unit 210, a storage unit 220, and an input/output unit 250. The storage unit 220 is constituted by a RAM 202, a ROM 203, an SSD 204, and the like (see FIG. 5), and stores data that is needed for processing for owner sameness confirmation including an encryption key, an electronic certificate, and identity confirmation information 222, which will be described below. In addition to the owner electronic certificate and the one-time electronic certificate, the electronic certificates include a model number electronic certificate including information on the model number (model) of the terminal 200.

The input/output unit 250 is constituted by including an NIC 205, an input/output interface 206, and a media drive 207 (see FIG. 5), and performs transmission and reception of communication data with another terminal 200 and the authentication station server 100. Also, the input/output unit 250 loads the terminal program 221 from a recording medium 299. Furthermore, the input/output unit 250 receives operations from the user of the terminal and displays information to the user.

The control unit 210 is constituted by including an electronic certificate request unit 211, a terminal authentication unit 212, a confirmation request start unit 213, a confirmation request start response unit 214, a confirmation request unit 215, a confirmation request transfer unit 216, a confirmation response transfer unit 217, and a sameness determination unit 218.

The electronic certificate request unit 211 requests issuance of the electronic certificate to the authentication station server 100.

The terminal authentication unit 212 authenticates the partner terminal 200 for which the sameness of the owner is to be confirmed, and decides on the identity confirmation information for confirming the sameness of the owners of the terminal 200 and the partner terminal 200 in order to confirm the owner sameness.

The identity confirmation information for confirming the sameness is an item (type) of the identity confirmation information for confirming that the owners are the same, such as the address, name, or driver's license number. For example, the terminal authentication unit 212 uses an item of the identity confirmation information 222 that is stored in common in both the terminal 200 and the partner terminal 200 as the item for confirming the sameness.

The confirmation request start unit 213 transmits a later-described terminal-issued confirmation request start message (see step S401 in FIG. 10, which will be described later) to the authentication station server 100.

The confirmation request start response unit 214 transmits the random number received from the authentication station server 100 to the partner terminal 200 (see step S405).

The confirmation request unit 215 transmits a confirmation request message (see step S408) including information (encrypted information) obtained by encrypting the identity confirmation information of the owner stored by the terminal 200 using a public key for homomorphic encryption to the partner terminal 200.

The confirmation request transfer unit 216 signs the above-described confirmation request message and transfers the signed confirmation request message as a confirmation request transfer message to the authentication station server 100 of the terminal 200 (see step S411 in FIG. 11, which will be described later).

The confirmation response transfer unit 217 signs the confirmation response message (see step S416) transmitted by the authentication station server 100, and transfers the signed confirmation response message as a confirmation response transfer message to the partner terminal (see step S417).

The sameness determination unit 218 receives the confirmation response transfer message and determines whether or not the owners of the two terminals 200 are the same.

Symbols

The symbols to be used in the description will be described before starting the description of the owner sameness confirmation processing.

I_d^(O) is the owner electronic certificate of a terminal d. The owner electronic certificate is issued by the authentication station server 100 to the terminal 200. The issued owner electronic certificate is stored in the electronic certificate database 130.

I_d^(P) is the one-time electronic certificate of the terminal d. The one-time electronic certificate is issued by the authentication station server 100 that issued the owner electronic certificate to the terminal 200. The issued one-time electronic certificate is stored in the electronic certificate database 130. The one-time electronic certificate need only be valid during the sameness confirmation processing, and the validity period thereof is shorter than the validity period of the owner electronic certificate.

I_d^(M) is the model number electronic certificate of the terminal d. The model number electronic certificate is issued by the authentication station server 100 to the terminal 200. The issued model number electronic certificate is stored in the electronic certificate database 130. The authentication station server 100 that issues the model number electronic certificate is not limited to being the same as the authentication station server 100 that issues the owner electronic certificate. There may also be an authentication station server 100 that issues only the model number electronic certificate and does not issue other types of electronic certificate.

I_d^(C) is the electronic certificate of the authentication station server d. The electronic certificate of the authentication station server 100 is issued by the route authentication station 300 (server of the route authentication station, see FIG. 1).

N_d1,d2 is a random number (nonce) generated from the authentication station d2 to the terminal d1.

V+W is data obtained by combining data V and data W.

M_S(M,K) is signed data obtained by signing the data M with the secret key K.

M_S(M,K1,K2) is double-signed data obtained by signing data M with a secret key K1 and further signing the signed data with a secret key K2.

Q_d is an issuance request application for the one-time electronic certificate transmitted from the terminal d to the authentication station server 100. Q_d includes a public key that is generated by the terminal d and is included in the one-time electronic certificate.

S_d^(O) is a secret key corresponding to the owner electronic certificate I_d^(O) of the terminal d.

S_d^(P) is the secret key corresponding to the one-time electronic certificate I_d of the terminal d.

S_d^(M) is the secret key corresponding to the model number electronic certificate I_d^(M) of the terminal d.

S_d^(C) is the secret key corresponding to the electronic certificate I_d^(C) of the authentication station d.

E_PK is an encryption formula for homomorphic encryption using a public key PK.

D_SK is a decryption formula for homomorphic encryption using a secret key SK. The pair of the public key PK and the secret key SK is generated by the terminal 200.

C_d1 is the result (written also as “encrypted information”) of performing encryption using the encryption formula E_PK for homomorphic encryption on the identity confirmation information calculated by the terminal d1. The details of the calculation method for the encryption information C_d1 will be described later.

C_d2′ is calculated by the authentication station d2 that received the encryption information C_d1. C_d2′ is the result (written also as “response encrypted information”) of calculating the encrypted information C_d1 and the result of performing encryption using the encryption formula E_PK for homomorphic encryption on the identity confirmation information through computation corresponding to homomorphic encryption. Details of the method for calculating the response encrypted information C_d2′ will be described later.

L_d1,d2 is a list of items of the identity confirmation information for performing owner sameness confirmation between the terminal d1 and the terminal d2.

Homomorphic Encryption

The homomorphic encryption E_PK is encryption according to which E_PK(M1+M2) can be calculated based on an encrypted text E_PK(M1) for unencrypted text M1 and an encrypted text E_PK(M2) for unencrypted text M2. Here, + is not limited to addition, and is some kind of binomial computation. For example, with RSA encryption, E_PK(M1)×E_PK(M2)=E_PK(M1×M2) is satisfied. That is, the decrypted product of the encrypted texts is the product of the unencrypted texts. ElGamal encryption is another example.

Also, in Paillier encryption, E_PK(M1)×E_PK(M2)=E_PK(M1+M2) is satisfied. That is, the decrypted product of the encrypted texts is the sum of the unencrypted texts. Elliptic curve cryptography is another example.

Hereinafter, a method for calculating the encrypted information C_d1 and the response encrypted information C_d2′ using Paillier encryption will be described. The secret keys for Paillier encryption are a prime number p and a prime number q with the same length. The public key is N=p×q.

The encryption function is written as E_N, and the decryption function is written as D_p,q.

The encrypted text for the unencrypted text M generates a random number r and satisfies E_N^(M)=(1+N)^M×r^N mod N². Hereinafter, description of mod N² will be omitted.

E_N (M1)=(1+N)^M1×r^N, and E_N (M2)=(1+N)^M2×s^N are satisfied. Here, the random number r and the random number s are random numbers that are generated when an unencrypted text M1 and an unencrypted text M2 are respectively encrypted. Upon doing so,

$E_N\left(M1\right)\times E_N\left(M2\right)={\left(1+N\right)}^{M1}\times r^N\times {\left(1+N\right)}^{M2}\times s^N={\left(1+N\right)}^{M1+M2}\times {\left(r\times s\right)}^N=E_N+\left(M1+M2\right)$

is satisfied, and therefore Paillier encryption is homomorphic encryption.

Next, a method for calculating the encrypted information C_d1 and the response encrypted information C_d2′ will be described. Hereinafter, the terminal 200B will be described as generating encrypted information C_d1 and the authentication station server 100A of the partner terminal 200A will be described as generating the response encrypted information C_d2′ (see FIGS. 10 and 11, which will be described later).

The identity confirmation information stored by the terminal 200B for which sameness is to be confirmed is VB, and the identity confirmation information stored by the authentication station server 100A is VA. Note that the pieces of identity confirmation information VA and VB are pieces of identity confirmation information that correspond to items included in the item list L_d1,d2 of the identity confirmation information.

Also, it is assumed that the terminal 200B calculates the encrypted information C_B, and the authentication station server 100A that has received the encrypted information C_B and the public key N of the terminal 200B calculates response encrypted information C_{CA_A}′. The terminal 200B generates a random number r, calculates encrypted information C_B=E_N(VB)=(1+N)^VB×r^N, which is the encrypted text of the identity confirmation information VB, and transmits the encrypted information C_B together with the public key N to the authentication station server 100A via the terminal 200A.

The authentication station server 100A generates a random number s and a random number t and calculates an encrypted text E_N(VA) by encrypting the identity confirmation information VA stored in the authentication station server 100A. Next, the authentication station server 100A calculates the response encrypted information C_{CA_A}′ as described below based on the encrypted information C_B(=E_N(VB)) and the encrypted text E_N(VA) and transmits the calculated response encrypted information C_{CA_A}′ to the terminal 200B.

$C_{\mathrm{CA}\_A}^{\prime }={\left(C_B\right)}^s\times {E_N\left(\mathrm{VA}\right)}^{-s}={\left(C_B\right)}^s\times {\left({\left(1+N\right)}^{\mathrm{VA}}\times t^N\right)}^{-s}$ $C_{\mathrm{CA}\_A}^{\prime }={\left({\left(1+N\right)}^{VB}\times r^N\right)}^s\times {\left(1+N\right)}^{-s\mathrm{VA}}\times t^{-sN}={\left(1+N\right)}^{sVB}\times r^{sN}\times {\left(1+N\right)}^{-s\mathrm{VA}}\times t^{-sN}={\left(1+N\right)}^{sVB}\times {\left(1+N\right)}^{-\mathrm{sVA}}\times r^{sN}\times t^{-\mathrm{sN}}={\left(1+N\right)}^{s\left(\mathrm{VB}-\mathrm{VA}\right)}\times {\left(r^s\times t^{-s}\right)}^N$

is satisfied, and therefore the result of the terminal 200B encrypting the response encrypted information C_{CA_A}′ is D_p,q(C_{CA_A}′)=s(VB−VA). Accordingly, if the decryption result is 0, it can be understood that the pieces of identity confirmation information VB and VA held by the terminal 200B and the authentication station server 100A are the same.

If the decryption result is not 0, the terminal 200B understands that the identity confirmation information does not match. Since the random number s is the random number generated by the authentication station server 100A and D_p,q(C_{CA_A}′)=s(VB−VA) is a random number, the terminal 200B cannot obtain the information regarding the identity confirmation information VA and the identity confirmation information VA does not leak out. Conversely, regarding the identity confirmation information VB of the terminal 200B, the authentication station server 100A acquires only the encrypted information C_B that was encrypted, and therefore the information cannot be obtained and the identity confirmation information VB does not leak out. That is, if the identity confirmation information does not match, neither the terminal 200B nor the authentication station server 100A leaks the identity confirmation information to its partner.

Although the foregoing is an example of sameness confirmation for identity confirmation information using Paillier encryption, it can be similarly carried out also through homomorphic encryption in which the product of the encrypted texts is the encryption of the sum of the unencrypted texts. E_PK is homomorphic encryption in which E_PK(M1)×E_PK(M2)=E_PK(M1+M2) is satisfied.

The terminal 200B calculates the encrypted information C_B=E_PK(VB) by encrypting the identity confirmation information VB and transmits the encrypted information C_B to the authentication station server 100A via the terminal 200A.

The authentication station server 100A generates the random number s, calculates the response encrypted information C_{CA_A}′ as described below, and transmits the result to the terminal 200B.

$C_{\mathrm{CA}\_A}^{\prime }={\left(C_B\right)}^s\times {E_{PK}\left(\mathrm{VA}\right)}^{-s}$ $C_{\mathrm{CA}\_A}^{\prime }={E_{PK}\left(\mathrm{VB}\right)}^s\times {E_{PK}\left(\mathrm{VA}\right)}^{-s}=E_{PK}\left(sVB\right)\times E_{PK}\left(-s\mathrm{VA}\right)=E_{PK}\left(sVB-s\mathrm{VA}\right)=E_{PK}\left(s\left(\mathrm{VB}-\mathrm{VA}\right)\right)$

is satisfied, and therefore upon decrypting the response encrypted information C_{CA_A}′, the terminal 200B obtains D_SK(C_{CA_A}′)=s(VB−VA) and can determine the sameness between the identity confirmation information VB and the identity confirmation information VA based on whether or not the decryption result is 0.

This is also similarly possible with homomorphic encryption in which the product of the encrypted texts is the encryption of the product of the unencrypted texts. E_PK is homomorphic encryption in which E_PK(M1)×E_PK(M2)=E_PK(M1×M2) is satisfied.

The terminal 200B calculates the encrypted information C_B=E_PK(VB) by encrypting the identity confirmation information VB and transmits the result to the authentication station server 100A.

The authentication station server 100A generates the random number s, calculates the response encrypted information C_{CA_A}′ as described below, and transmits the result to the terminal 200B.

$C_{\mathrm{CA}\_A}^{\prime }={\left(C_B\right)}^s\times {E_{PK}\left(\mathrm{VA}\right)}^{-s}$ $C_{\mathrm{CA}\_A}^{\prime }={E_{PK}\left(\mathrm{VB}\right)}^s\times {E_{PK}\left(\mathrm{VA}\right)}^{-s}={E_{PK}\left(\mathrm{VB}\right)}^s\times E_{PK}\left({\mathrm{VA}}^{-s}\right)=E_{PK}\left(V{B}^s\times {\mathrm{VA}}^{-s}\right)=E_{PK}\left({\left(\mathrm{VB}/\mathrm{VA}\right)}^s\right)$

is satisfied, and therefore upon decrypting the response encrypted information C_{CA_A}′, the terminal 200B obtains D_SK (C_{CA_A}′)=(VB−VA) s and can determine the sameness between the identity confirmation information VB and the identity confirmation information VA based on whether or not the decryption result is 1.

As described above, the terminal 200B encrypts the identity confirmation information VB stored in the terminal 200B using homomorphic encryption and transmits the result as the encrypted information C_B(=E_PK(VB)) to the authentication station server 100A. The authentication station server 100A calculates the response encrypted information C_{CA_A}′ by multiplying together the result (E_PK(VA)) of encrypting the identity confirmation information VA stored in the authentication station server 100A and the received encrypted information C_B, and transmits the calculated response encrypted information C_{CA_A}′ to the terminal 200B. If the result of decrypting the response encrypted information C_{CA_A}′ is a predetermined value (0 or 1 in the above-described example), the terminal 200B determines that the pieces of identity confirmation information stored in both the terminal 200B and the authentication station server 100A are the same.

In the following description, when a signature generated using a secret key S is verified, a public key is acquired from the electronic certificate corresponding to the secret key S, and the signature is verified using the public key. If verification of the signature fails, processing for issuing an owner electronic certificate, processing for issuing a one-time electronic certificate, and processing for confirming the sameness of the owners are canceled.

Note that a signature of the authentication station server 100 is given to the electronic certificate, and the signature of the electronic certificate is verified using the public key of the authentication station server 100. The public key of the authentication station server 100 is acquired after the signature of the electronic certificate of the authentication station server 100 issued by the route authentication station 300 (see FIG. 1) is verified using the public key of the route authentication station 300. Note that the public key of the route authentication station 300 is stored in the storage units 120 and 220 (see FIGS. 3 and 6). Also, a validity period is included in the electronic certificate. If no verification time is included in the validity period, the verification of the electronic certificate fails.

The electronic certificate includes identification information of the authentication station (authentication station server 100) that issued the electronic certificate as the issuer (Issuer field), and the authentication station of the electronic certificate from which the public key is to be acquired is understood.

Processing for Issuing Owner Electronic Certificate

FIG. 7 is a sequence diagram showing processing for issuing an owner electronic certificate according to the present embodiment. Processing in which the authentication station server 100A issues the owner electronic certificate to the terminal 200A will be described with reference to FIG. 7.

In step S101, the electronic certificate request unit 211 of the terminal 200A generates a key pair (a secret key and a public key) for public key encryption.

In step S102, the electronic certificate request unit 211 transmits the public key generated in step S101 and information on the identity confirmation document to the authentication station server 100A, and requests issuance of the owner electronic certificate. This transmitted message may also be signed with the secret key generated in step S101.

In step S103, the electronic certificate issuance unit 111 of the authentication station server 100A confirms that the identity confirmation document received in step S102 is authentic. Next, the electronic certificate issuance unit 111 confirms that the owner of the terminal 200A and the person described in the identity confirmation document match each other.

In step S104, the electronic certificate issuance unit 111 adds a record to the electronic certificate database 130 (see FIG. 4), and stores the information of the identity confirmation document and the identity information (address, name, etc.; also written as “identity confirmation information”) described in the identity confirmation document in the identity confirmation information 135.

In step S105, the electronic certificate issuance unit 111 issues an owner electronic certificate I_A^(O) including the public key received in step S102. The key owner (Subject field) of the owner electronic certificate is the entirety or part of the identity confirmation information of the owner, such as the name or address, which was confirmed in step S103. The electronic certificate issuance unit 111 stores the serial number of the issued owner electronic certificate in the identification information 131 of the record added in step S104. Furthermore, the electronic certificate issuance unit 111 stores “owner” in the type 132, the key owner in the key owner 133, “-” in the related certificate 134, and the data of the issued owner electronic certificate in the electronic certificate 136.

In step S106, the electronic certificate issuance unit 111 transmits the issued owner electronic certificate I_A^(O) as a response to the request made in step S102 to the terminal 200A.

In step S107, the electronic certificate request unit 211 of the terminal 200A verifies the signature of the authentication station server 100A of the received owner electronic certificate I_A^(O).

In step S108, the electronic certificate request unit 211 of the terminal 200A stores the received owner electronic certificate I_A^(O) in the storage unit 220. Also, the electronic certificate request unit 211 stores the identity confirmation information included as the value of the key owner (Subject field) of the owner electronic certificate I_A^(O) in the identity confirmation information 222 (see FIG. 6).

The foregoing described processing in which the authentication station server 100A issues an owner electronic certificate to the terminal 200A. Similarly, the authentication station server 100B issues the owner electronic certificate to the terminal 200B. The processing in which the authentication station server 100B issues the owner electronic certificate to the terminal 200B is similar to that of FIG. 7, and therefore description thereof is omitted. In this state, the terminals 200A and 200B store the owner electronic certificate and the secret key corresponding thereto. Also, the authentication station servers 100A and 100B store the identity confirmation information in association with the owner electronic certificate. The terminals 200A and 200B store the identity confirmation information 222 (see FIG. 6).

Processing for Issuing One-Time Electronic Certificate

FIG. 8 is a sequence diagram showing processing for issuing a one-time electronic certificate according to the present embodiment. Processing in which the authentication station server 100A issues the one-time electronic certificate to the terminal 200A will be described with reference to FIG. 8.

In step S201, the electronic certificate request unit 211 of the terminal 200A generates a key pair (a secret key and a public key) for public key encryption.

In step S202, the electronic certificate request unit 211 transmits a request to issue the one-time electronic certificate including the public key generated in step S201 to the authentication station server 100A. Specifically, the electronic certificate request unit 211 generates M_S(Q_A,S_A^(P)), which includes a public key and is obtained by signing an issuance request application Q_A for the one-time electronic certificate with the secret key generated in step S201. Next, the electronic certificate request unit 211 generates M_S(M_S(Q_A,S_A^(P))+I_A^(O)+I_A^(M),S_A^(O),S_A^(M)) by combining the owner electronic certificate I_A^(O) and model number electronic certificate I_A^(M) of the terminal 200A with the signed data, and signing the result using the secret key S_A^(O) of the owner electronic certificate and the secret key S_A^(M) of the model number electronic certificate of the terminal 200A. The electronic certificate request unit 211 transmits M_S(M_S(Q_A,S_A^(P))+I_A^(O)+I_A(M),S_A^(O),S_A^(M)) to the authentication station server 100A as a request to issue the one-time electronic certificate.

In step S203, the electronic certificate issuance unit 111 of the authentication station server 100A verifies the signatures provided using the secret keys S_A(M),S_A^(O), and S_A^(P) of the request to issue the one-time electronic certificate received in step S202.

In step S204, the electronic certificate issuance unit 111 issues the one-time electronic certificate I_A^(P) including the public key included in Q_A received in step S202. The key owner of the one-time electronic certificate is a random character string.

In step S205, the electronic certificate issuance unit 111 stores the one-time electronic certificate I_A^(P) in association with the owner electronic certificate I_A^(O). Specifically, the electronic certificate issuance unit 111 adds a record to the electronic certificate database 130 (see FIG. 4) and stores the serial number of the one-time electronic certificate issued in the identification information 131. Furthermore, the electronic certificate issuance unit 111 stores “one-time” in the type 132, the key owner in the key owner 133, “-” in the identity confirmation information 135, and the data of the issued one-time electronic certificate in the electronic certificate 136. The electronic certificate issuance unit 111 stores the serial number of the owner electronic certificate I_A^(O) received in step S202 in the related certificate 134. The authentication station server 100 accesses the identity confirmation information for the owner of the terminal 200 for which the one-time electronic certificate was issued, by referencing the identity confirmation information 135 of the electronic certificate corresponding to the related certificate 134 of the one-time electronic certificate.

In step S206, the electronic certificate issuance unit 111 sends the issued one-time electronic certificate I_A^(P) as a response to the terminal 200A. Specifically, the electronic certificate issuance unit 111 combines the electronic certificate I_A^(C) of the authentication station server 100A with the one-time electronic certificate I_A^(P) and transmits M_S(I_A^(P)+I_A^(C),S_A^(C)) signed using the secret key S_A^(C) corresponding to the electronic certificate I_A^(C) as a response to the request made in step S202.

In step S207, the electronic certificate request unit 211 of the terminal 200A verifies the signature provided using the secret key S_A^(C) of the received M_S(I_A^(P)+I_A^(C),S_A^(C)) and the signature of the one-time electronic certificate I_A^(P). In step S208, the electronic certificate request unit 211 of the terminal 200A stores the one-time electronic certificate I_A^(P) in the storage unit 220.

The foregoing described processing in which the authentication station server 100A issues a one-time electronic certificate to the terminal 200A. Similarly, the authentication station server 100B issues the one-time electronic certificate to the terminal 200B. The processing in which the authentication station server 100B issues the one-time electronic certificate to the terminal 200B is similar to that of FIG. 8, and therefore description thereof is omitted. In this state, the terminals 200A and 200B store the one-time electronic certificate and the secret key corresponding thereto. Also, the authentication station servers 100A and 100B store the one-time electronic certificate in association with the owner electronic certificate, and consequently, in association with the identity confirmation information.

Owner Sameness Confirmation Processing: Processing Between Terminals

The terminal 200B and the partner terminal 200A for which the sameness of the owner is to be confirmed obtain the one-time electronic certificate, and thereafter the terminal 200B requests owner sameness confirmation to the authentication station server 100A via the partner terminal 200A. Before the request is made, the terminals 200A and 200B perform mutual authentication, and thereafter determine the item of the identity confirmation information for which the sameness is to be confirmed. For example, the terminals 200A and 200B use an item held in common in the pieces of identity confirmation information 222 (see FIG. 6) registered in both terminals 200A and 200B as the item of the identity confirmation information for confirming the sameness.

Processing performed up to when the terminals 200A and 200B decide on the item of the identity confirmation information for confirming the sameness will be described with reference to FIG. 9, which will be described later. Then, processing in which the terminal 200B requests owner sameness confirmation to the authentication station server 100A via the partner terminal 200A will be described with reference to FIGS. 10 and 11, which will be described later.

FIG. 9 is a sequence diagram (1) for owner sameness confirmation processing according to the present embodiment. Mainly the processing performed between the terminals 200A and 200B in the owner sameness confirmation processing will be described with reference to FIG. 9.

In step S301, the terminal authentication unit 212 of the terminal 200A transmits the one-time electronic certificate I_A^(P) to the partner terminal 200B. The terminal 200B verifies the signature of the received one-time electronic certificate I_A^(P).

In step S302, the terminal authentication unit 212 of the terminal 200B transmits the one-time electronic certificate I_B^(P) to the partner terminal 200A. The terminal 200A verifies the signature of the received one-time electronic certificate I_B^(P).

In step S303, the terminal authentication units 212 of the terminal 200A and 200B authenticate each other using the secret keys S_A^(P) and S_B^(P) corresponding to the one-time electronic certificate. For example, the terminal 200A generates the random number, transmits the random number to the terminal 200B, and requests a signature provided using the secret key corresponding to the one-time electronic certificate I_B^(P) for the random number. The terminal 200A can authenticate that the terminal 200B has a secret key corresponding to the one-time electronic certificate I_B^(P) by verifying the signature generated by the terminal 200B. Similarly, the terminal 200B can authenticate that the terminal 200A has the secret key corresponding to the one-time electronic certificate I_A^(P).

In step S304, the terminal authentication unit 212 determines the item list L_A,B of the identity confirmation information for which the sameness is to be confirmed. Specifically, the terminal authentication unit 212 uses items that are held in common between the pieces of identity confirmation information 222 (see FIG. 6) stored in both of the terminals 200A and 200B as the item list L_A,B of the identity confirmation information.

Owner Sameness Confirmation Processing: Processing Between Terminal and Authentication Station Server FIG. 10 is a sequence diagram (2) of owner sameness confirmation processing according to the present embodiment.

FIG. 11 is a sequence diagram (3) of owner sameness confirmation processing according to the present embodiment. Processing performed between the terminal 200B and the authentication station server 100A via the terminal 200A in the owner sameness confirmation processing will be described with reference to FIGS. 10 and 11.

In step S401, the confirmation request start unit 213 of the terminal 200A transmits the terminal-issued confirmation request start message to the authentication station server 100A. Specifically, the confirmation request start unit 213 generates M_S(L_A,B+I_A^(P)+I_B^(P)+I_A^(M),S_A^(P),S_A^(M)) by combining the item list L_A,B of the identity confirmation information, the one-time electronic certificates I_A^(P) and I_B^(P) of the terminals 200A and 200B, and the model number electronic certificate I_A^(M) and signing using the secret key S_A^(P)) of the one-time electronic certificate and the secret key S_A^(M) of the model number electronic certificate of the terminal 200A. The confirmation request start unit 213 transmits M_S(L_A,B+I_A^(P)+I_B^(P)+I_A^(M),S_A^(P),S_A^(M)) as the terminal-issued confirmation request start message to the authentication station server 100A.

In step S402, the confirmation reception unit 112 of the authentication station server 100A verifies the signatures provided using the secret keys S_A^(M) and S_A^(P) of the terminal-issued confirmation request start message.

In step S403, the confirmation reception unit 112 generates a random number N_A,A and a random number N_B,A.

In step S404, the confirmation reception unit 112 transmits the random number N_A,A and the random number N_B,A as a response to the request made in step S401.

In step S405, the confirmation request start response unit 214 of the terminal 200A transmits the random number N_B,A to the terminal 200B.

In step S406, the confirmation request unit 215 of the terminal 200B generates a key pair for homomorphic encryption.

In step S407, the confirmation request unit 215 calculates encrypted information C_B using homomorphic encryption. Specifically, the confirmation request unit 215 calculates the encrypted information C_B by acquiring, from the identity confirmation information 222 (see FIG. 6), the identity confirmation information of the owner corresponding to the item list L_A,B of the identity confirmation information for confirming the sameness, which was determined in step S304 (see FIG. 9), and encrypting the acquired identity confirmation information.

In step S408, the confirmation request unit 215 transmits the confirmation request message to the terminal 200A. Specifically, the confirmation request unit 215 transmits, to the terminal 200A, M_S(L_A,B+I_B^(P)+I_A^(P)+N_B,A+PK_B+C_B^(M)+I_B^(M),S_B^(P),S_B^(M)), which is obtained by combining the item list L_A,B of the identity confirmation information stored in the terminal 200B, the one-time electronic certificates I_B^(P), I_A^(P) of the terminal 200B and the partner terminal 200A, the random number N_B,A, a public key PK_B for homomorphic encryption, the encrypted information C_B, and a model number electronic certificate I_B^(M), and signing using the secret keys S_B^(P) and S_B^(M). Hereinafter, M_S(L_A,B+I_B^(P)+I_A^(P)+N_B,A+PK_B+C_B+I_B^(M),S_B^(P),S_B^(M)) will be written also as U_A,B.

In step S409, the confirmation request transfer unit 216 of the terminal 200A verifies the signature provided using the secret keys S_B^(M) and S_B^(P) of U_A,B.

In step S410, the confirmation request transfer unit 216 confirms that the item list L_A,B received in step S408 and the item list L_A,B that was determined in step S304 (see FIG. 9) and is stored in the terminal 200A match each other. If they do not match, the confirmation request transfer unit 216 cancels the owner sameness confirmation processing.

The description of the owner sameness confirmation processing will be continued with reference to FIG. 11.

In step S411, the confirmation request transfer unit 216 transmits a confirmation request transfer message to the authentication station server 100A. Specifically, the confirmation request transfer unit 216 transmits M_S(U_A,B+N_A,A+I_A^(P)+I_A^(M),S_A^(P),S_A^(M)), which is obtained by combining U_A,B, the random number N_A,A, the one-time electronic certificate I_A^(P), and the model number electronic certificate I_A^(M), and signing using the secret keys S_A^(P) and S_A^(M), as a confirmation request transfer message to the authentication station server 100A.

In step S412, the confirmation response unit 113 of the authentication station server 100A verifies the signatures provided using the secret keys S_A^(M) and S_A^(M) of the confirmation request transfer message. Also, the confirmation response unit 113 verifies the signatures provided using the secret keys S_B^(M) and S_B^(P) of U_A,B, which is included in the confirmation request transfer message.

In step S413, the confirmation response unit 113 compares whether or not the one-time electronic certificate I_A^(P) included in the confirmation request transfer message is the same as the one-time electronic certificate I_A^(P) that was included in step S401 (see FIG. 10). If they are not the same, the confirmation response unit 113 cancels the owner sameness confirmation processing.

In step S414, the confirmation response unit 113 verifies whether or not the random number N_A,A included in the confirmation request transfer message and the random number N_B,A included in U_A,B in the confirmation request transfer message are respectively the same as the random number N_A,A and the random number N_B,A transmitted in step S404 (see FIG. 10). If they are not the same, the confirmation response unit 113 cancels the owner sameness confirmation processing.

In step S415, the confirmation response unit 113 generates the response encrypted information C_{CA_A}′ based on the received encrypted information C_B and the identity confirmation information held by the authentication station server 100A. Specifically, the confirmation response unit 113 acquires the one-time electronic certificate I_A^(P) included in U_A,B and the item list L_A,B of the identity confirmation information in the confirmation request transfer message. The confirmation response unit 113 specifies the owner electronic certificate I_A^(O) of the terminal 200A from the related certificate 134 of the record of the one-time electronic certificate I_A^(P) in the electronic certificate database 130, and acquires the identity confirmation information 135 thereof. Next, the confirmation response unit 113 acquires the identity confirmation information in the item list L_A,B of the identity confirmation information from the identity confirmation information 135. Finally, the confirmation response unit 113 generates the response encrypted information C_{CA_A}′ based on the encrypted information C_B, the public key PK_B, and the acquired identity confirmation information.

In step S416, the confirmation response unit 113 transmits M_S(I_B^(P)+I_A^(P)+C_{CA_A}′+I_A^(C),S_A^(C)), which is obtained by combining the one-time electronic certificates I_B^(P) and I_A^(P), the response encrypted information C_{CA_A}′, and the authentication station electronic certificate I_A^(C), and signing using the secret key S_A^(C), as a confirmation response message to the terminal 200A as a response.

In step S417, the confirmation response transfer unit 217 of the terminal 200A transfers the confirmation response message received from the authentication station server 100A in step S416 to the terminal 200B.

In step S418, the sameness determination unit 218 of the terminal 200B verifies the signature provided using S_A^(C) in the confirmation response message.

In step S419, the sameness determination unit 218 decrypts the response encrypted information C_{CA_A}′ using the secret key for homomorphic encryption.

In step S420, if the decryption result is 0 (step S420→YES), the sameness determination unit 218 advances to step S421, and if the decryption result is not 0 (step S420→NO), the sameness determination unit 218 advances to step S422. Note that a decryption result of 0 is a predetermined value in the case where the homomorphic encryption is Paillier encryption (homomorphic encryption in which the product of the encrypted texts is encryption of the sum of unencrypted texts). In the case of homomorphic encryption in which the product of the encrypted texts is the encryption of the product of the unencrypted texts, determination is performed based on whether or not the decryption result is 1.

In step S421, the sameness determination unit 218 determines that the owners are the same.

In step S422, the sameness determination unit 218 determines that the owners are different.

With that, the terminal 200B ends the owner sameness confirmation processing for confirming that the owner of the terminal 200B and the owner of the terminal 200A match each other in the authentication station server 100A via the terminal 200A. Next, the terminals 200B and 200A are switched, and the terminal 200A confirms that the owner of the terminal 200A and the owner of the partner terminal 200B match each other. Specifically, similarly to the steps of step S401 and onward, the terminal 200A confirms that the owner of the terminal 200A and the owner of the partner terminal 200B match each other in the authentication station server 100B via the terminal 200B. This processing for confirming is similar to that shown in FIGS. 10 and 11, and therefore description thereof is omitted.

Both of the terminals 200A and 200B confirm that the owners are the same, whereby the owner sameness confirmation processing ends. After the end of the owner sameness confirmation processing, the terminals 200A and 200B performs sharing (copy) processing of a secret key to be used for authentication during, for example, service usage, data that is needed for content copyright management, and the like.

Features of Owner Sameness Certificate Processing

The one-time electronic certificate and the model number electronic certificate are examples of terminal information of the terminal that is to be transmitted to the partner terminal for which the sameness of the owner is to be confirmed. Information regarding the owner is not included in any electronic certificate. For this reason, there is no risk that personal information including the identity confirmation information of the owner will leak out to the partner terminal.

Even if the authentication station servers are different, it is possible to confirm whether or not the owners of two terminals are the same by comparing the item of the identity confirmation information that is stored in common. Also, the identity confirmation information (see the identity confirmation information 135 in FIG. 4 and the identity confirmation information 222 in FIG. 6) is authentic information acquired from the identity confirmation document (see steps S103, S104, and S108 in FIG. 7), and the owner sameness confirmation system 10 confirms the sameness of the owners based on highly-reliable identity confirmation information.

The terminal and the authentication station server compare the items of the identity confirmation information respectively stored in the terminal and the authentication station server in a state of being encrypted using homomorphic encryption. For this reason, it is possible to confirm whether or not the identity confirmation information matches without the identity confirmation information flowing out to the partner.

The authentication station server acquires the model number electronic certificate, and therefore it is possible to find out the model numbers (models) of the two terminals for which the sameness of the owners is to be confirmed, and it is possible to obtain information for improving the service.

Variation: Item List of Identity Confirmation Information

The item list L_A,B of the identity confirmation information is items of the identity confirmation information 222 stored in both terminals 200A and 200B (see the description of the terminal authentication unit 212 in FIG. 6 and step S304 in FIG. 9). The terminal 200 may also determine the item list L_A,B according to the degree of importance of the data to be shared after the sameness confirmation. For example, if a secret key for accessing a financial service is shared, the terminal 200 uses an address and a name as the item list L_A,B. Also, in the case of sharing a secret key for accessing a service with a family discount between family members that live together, the terminal 200 uses only an address of the item list L_A,B.

Note that if the identity confirmation information (item of the identity confirmation information) for which sameness is to be confirmed has been determined in advance, the terminal 200 or the authentication station server 100 may also execute the processing for owner sameness confirmation without using the item list L_A,B.

Variation: Model Number Electronic Certificate

The terminal-issued confirmation request message (step S401 in FIG. 10) and the confirmation request message (step S408) include the model number electronic certificate, and the authentication station server 100 can acquire the model number of the terminal 200 by verifying the signature of the secret key corresponding to the model number electronic certificate. Provision of the model number electronic certificate or the corresponding signature may also be omitted. A signature provided using a secret key corresponding to the one-time electronic certificate is provided in the message, and thus security is ensured.

Variation: Electronic Certificate Database

In the above-described embodiment, there is no information in the identity confirmation information 135 in the record of the one-time electronic certificate stored in the electronic certificate database 130 (FIG. 4). Instead, the confirmation response unit 113 acquires the identity confirmation information from the identity confirmation information 135 of the record of the owner electronic certificate shown in the related certificate 134 (see step S415 in FIG. 11).

In contrast to this, the identity confirmation information 135 of the record of the owner electronic certificate shown in the related certificate 134 may also be stored in the identity confirmation information 135 of the record of the one-time electronic certificate. The authentication station server 100 can acquire the identity confirmation information directly from the record of the one-time electronic certificate.

Variation: Communication Route Between Terminal and Authentication Station Server

In the above-described embodiment, the terminal 200B and the authentication station server 100A exchange messages via the terminal 200A, but they may also exchange messages directly. Specifically, the confirmation request message transmitted by the terminal 200B (see step S408 in FIG. 10) is received by the authentication station server 100A as part of the confirmation request transfer message (see step S411 of FIG. 11) via the terminal 200A. The terminal 200B may also directly transmit the confirmation request message to the authentication station server 100A. The authentication station server 100A may also directly transmit the confirmation response message (see step S416) as well to the terminal 200B instead of via the terminal 200A.

Variation: Identity Confirmation Information of Terminal

In the above-described embodiment, the identity confirmation information 222 (see FIG. 6) stored in the terminal 200 is the value of the key owner of the owner certificate (see step S108 in FIG. 7). In contrast to this, the identity confirmation information 222 may also be the same as the identity confirmation information stored in the authentication station server 100. Specifically, in step S106, the authentication station server 100A signs data obtained by combining the owner certificate I_A^(O) and the identity confirmation information stored in the electronic certificate database 130 using the secret key S_A^(C) and transmits the result to the terminal 200A. The terminal 200A may also verify the signature and store the received identity confirmation information in the identity confirmation information 222.

Other Variations

Note that the present invention is not limited to the above-described embodiment and can be modified without departing from the gist of the invention.

For example, although the terminal 200 generates the key pair for homomorphic encryption each time owner sameness confirmation processing is performed (see step S406 of FIG. 10), a key pair that was generated before may also be re-used.

Also, the key owner of the one-time electronic certificate is a random character string, but need only be information that is unrelated to the identity confirmation information of the owner, and for example, may also be information generated based on the address of the terminal, a time at which there was a request to issue the electronic certificate, and the like.

In addition, in the above-described embodiment, the server that issues the electronic certificate and the server that confirms the sameness of the owners were the same authentication station server 100, but they may also be separate servers.

Also, in step S103 (see FIG. 7), the authentication station server 100 confirms the identity confirmation document, but confirmation may also be performed manually online.

Although several embodiments of the present invention were described above, these embodiments are merely exemplary and do not limit the technical scope of the present invention. The present invention can take various other embodiments, and furthermore, various modifications such as omission and replacement can be performed without departing from the gist of the present invention. These embodiments and variations are encompassed in the scope and gist of the invention described in the present specification and the like, and are encompassed in the invention described in the patent claims and its range of equivalency.

Effects

Hereinafter, effects of the owner sameness confirmation system 10 will be described.

The owner sameness confirmation system 10 according to the present embodiment is an owner sameness confirmation system 10 constituted by including a plurality of terminals 200 and a plurality of authentication station servers 100, in which each of the terminals 200B includes: a storage unit 220 configured to store identity confirmation information 222 of an owner of the terminal 200B; and a confirmation request unit 215 configured to transmit a confirmation request message including encrypted information obtained by encrypting the identity confirmation information of the owner of the terminal 200B using a public key for homomorphic encryption, an electronic certificate of a partner terminal 200A that is a target of owner sameness confirmation, and the public key, to an authentication station server 100A that issued the electronic certificate to the partner terminal 200A, the authentication station server 100A that issued the electronic certificate to the partner terminal 200A includes: a storage unit 120 configured to store the electronic certificate issued to the partner terminal 200A and identity confirmation information of an owner of the partner terminal 200A in association with each other; and a confirmation response unit 113 configured to, upon receiving the confirmation request message, acquire the identity confirmation information of the owner of the partner terminal 200A from the electronic certificate of the partner terminal 200A, and transmit a confirmation response message including response encrypted information, which is the result of calculating an encrypted text obtained by encrypting the identity confirmation information using the public key and the encrypted information through computation corresponding to the homomorphic encryption, as a response to the terminal 200B, and each of the terminals 200B further includes a sameness determination unit 218 configured to decrypt the response encrypted information, and determine whether or not the identity confirmation information of the owner of the terminal 200B and the identity confirmation information of the owner of the partner terminal 200A match each other based on whether or not the decryption result matches a predetermined value.

With this kind of owner sameness confirmation system 10, it is possible to determine whether or not the owners are the same for the terminal 200B and the partner terminal 200A, for which the authentication station servers 100 that issued the electronic certificates are different. Specifically, the terminal 200B can perform determination through processing with the authentication station server 100A that issued the electronic certificate to the partner terminal 200A. Also, the identity confirmation information is encrypted and exchanged (encrypted information and response encrypted information), and thus it is possible to confirm whether or not the identity confirmation information matches without the identity confirmation information flowing out between the terminal 200B and the authentication station server 100A. The same applies also for the terminal 200A, and it is possible to determine whether or not the owners are the same through processing with the authentication station server 100B without the identity confirmation information flowing out.

Accordingly, with the owner sameness confirmation system 10, it is possible to enable owner sameness confirmation between terminals while ensuring security.

In the owner sameness confirmation system 10 according to the present embodiment, the identity confirmation information is constituted by one or more items, the confirmation request unit 215 calculates the encrypted information by encrypting the identity confirmation information for an item for confirming the sameness using the public key, the item being selected from among the one or more items, and transmits the item in a state of being included in the confirmation request message, the confirmation response unit 113 generates the encrypted text obtained by encrypting the identity confirmation information for the item of the owner of the partner terminal 200A using the public key, calculates the response encrypted information, and transmits the calculated response encrypted information as a response, and the sameness determination unit 218 decrypts the response encrypted information and determines whether or not the identity confirmation information for the item of the owner of the terminal 200B and the identity confirmation information for the item of the owner of the partner terminal 200A match each other based on whether or not the decryption result matches the predetermined value.

According to this kind of owner sameness confirmation system 10, it is possible to confirm the sameness of the owner using part (an item) of the identity confirmation information instead of the entirety thereof. For this reason, even if the registered pieces of identity confirmation information are different, it is possible to confirm the sameness of the owners due to parts of the identity confirmation information matching each other.

In the owner sameness confirmation system 10 according to the present embodiment, E, which is the homomorphic encryption, is homomorphic encryption in which E(M1)×E(M2)=E(M1+M2) is satisfied for unencrypted texts M1 and M2, the confirmation request unit 215 transmits E(V1) as the encrypted information for identity confirmation information V1 of the owner of the terminal 200B, the confirmation response unit 113 generates a random number r for identity confirmation information V2 of the owner of the partner terminal 200A and transmits E(V1)^r×E(V2)^−r as the response encrypted information as a response, and the sameness determination unit 218 determines whether or not V1 and V2 match each other based on whether or not the decryption result of the response encrypted information is 0, which is the predetermined value.

According to this kind of owner sameness confirmation system 10, the terminal 200 can confirm whether or not the pieces of identity confirmation information match each other using homomorphic encryption E, in which E(M1)×E(M2)=E(M1+M2) is satisfied for unencrypted texts M1 and M2.

Also, when the pieces of identity confirmation information V1 and V2 are different from each other, (V1−V2)≠0 is satisfied, and therefore r(V1−V2), which is the result of decrypting the response encrypted information, is a random number for the terminal 200B. For this reason, even if the terminal 200B knows the identity confirmation information V1, the information of the identity confirmation information V2 cannot be obtained, and thus the identity confirmation information V2 of the owner of the partner terminal 200B does not leak out. The same applies even if the terminals 200B and 200A are switched.

In the owner sameness confirmation system 10 according to the present embodiment, E, which is the homomorphic encryption, is homomorphic encryption in which E(M1)×E(M2)=E(M1×M2) is satisfied for unencrypted texts M1 and M2, the confirmation request unit 215 transmits E(V1) as the encrypted information for identity confirmation information V1 of the owner of the terminal 200B, the confirmation response unit 113 generates a random number r for identity confirmation information V2 of the owner of the partner terminal 200A and transmits E(V1)^r×E(V2)^−r as the response encrypted information as a response, and the sameness determination unit 218 determines whether or not V1 and V2 match each other based on whether or not the decryption result of the response encrypted information is 1, which is the predetermined value.

According to this kind of owner sameness confirmation system 10, the terminal 200 can confirm whether or not the pieces of identity confirmation information match each other using homomorphic encryption E, in which E(M1)×E(M2)=E(M1×M2) is satisfied for unencrypted texts M1 and M2.

Also, when the pieces of identity confirmation information V1 and V2 are different from each other, (V1/V2)≠1 is satisfied, and therefore (V1/V2)^r, which is the result of decrypting the response encrypted information, is a random number for the terminal 200B. For this reason, even if the terminal 200B knows the identity confirmation information V1, the information of the identity confirmation information V2 cannot be obtained, and thus the identity confirmation information V2 of the owner of the partner terminal 200B does not leak out. The same applies even if the terminals 200B and 200A are switched.

In the owner sameness confirmation system 10 according to the present embodiment, the confirmation request unit 215 transmits the confirmation request message via the partner terminal 200A to the authentication station server 100A that issued the electronic certificate to the partner terminal 200A, and the confirmation response unit 113 transmits the confirmation response message via the partner terminal 200A to the terminal 200B.

According to this kind of owner sameness confirmation system 10, the authentication station server 100 can limit the terminal 200 that is the communication partner to the terminal 200 to which the authentication station server 100 issued the electronic certificate. Consequently, communication from an unspecified terminal 200 can be avoided, whereby security is improved.

In the owner sameness confirmation system 10 according to the present embodiment, a value of a key owner included in the electronic certificate issued to the terminal 200 is identification information of the terminal 200 that is unrelated to the identity confirmation information of the owner of the terminal 200.

According to this kind of owner sameness confirmation system 10, it is possible to determine whether or not the owners of the two terminals 200 are the same using the one-time certificate that does not include the identity confirmation information of the owner. For this reason, the terminal 200 can confirm the sameness of the owners without leaking the identity confirmation information of the owner of the terminal 200 to the authentication station server 100 of the partner terminal 200.

In the owner sameness confirmation system 10 according to the present embodiment, the confirmation request message transmitted by the terminal 200 is signed using at least any one of a secret key corresponding to the electronic certificate and a secret key corresponding to a model number electronic certificate indicating a model number of the terminal 200.

According to this kind of owner sameness confirmation system 10, the authentication station server 100 can acquire the model number (model) of the terminal 200. For this reason, the operator of the authentication station server 100 can obtain information for service improvement.

REFERENCE SIGNS LIST

• 10 Owner sameness confirmation system
• 100, 100A, 100B Authentication station server
• 111 Electronic certificate issuance unit
• 112 Confirmation reception unit
• 113 Confirmation response unit
• 130 Electronic certificate database
• 200, 200A, 200B Terminal
• 211 Electronic certificate request unit
• 212 Terminal authentication unit
• 213 Confirmation request start unit
• 214 Confirmation request start response unit
• 215 Confirmation request unit
• 216 Confirmation request transfer unit
• 217 Confirmation response transfer unit
• 218 Sameness determination unit
• 222 Identity confirmation information

Claims

1. An owner sameness confirmation system including a plurality of terminals and a plurality of authentication station servers, wherein each of the terminals includes:a first storage unit configured to store identity confirmation information of an owner of the terminal; anda confirmation request unit, including one or more processors, configured to transmit a confirmation request message including encrypted information obtained by encrypting the identity confirmation information of the owner of the terminal using a public key for homomorphic encryption, an electronic certificate of a partner terminal that is a target of owner sameness confirmation, and the public key, to an authentication station server that issued the electronic certificate to the partner terminal,the authentication station server that issued the electronic certificate to the partner terminal includes:a second storage unit configured to store the electronic certificate issued to the partner terminal and identity confirmation information of an owner of the partner terminal in association with each other; anda confirmation response unit, including one or more processors, configured to, upon receiving the confirmation request message, acquire the identity confirmation information of the owner of the partner terminal from the electronic certificate of the partner terminal, and transmit a confirmation response message including response encrypted information, which is the result of calculating an encrypted text obtained by encrypting the identity confirmation information using the public key and the encrypted information through computation corresponding to the homomorphic encryption, as a response to the terminal, andeach of the terminals further includesa sameness determination unit, including one or more processors, configured to decrypt the response encrypted information, and determine whether or not the identity confirmation information of the owner of the terminal and the identity confirmation information of the owner of the partner terminal match each other based on whether or not the decryption result matches a predetermined value.

2. The owner sameness confirmation system according to claim 1, wherein the identity confirmation information is constituted by one or more items,the confirmation request unit is configured to calculate the encrypted information by encrypting the identity confirmation information for an item for confirming the sameness using the public key, the item being selected from among the one or more items, and transmits the item in a state of being included in the confirmation request message,the confirmation response unit is configured to generate the encrypted text obtained by encrypting the identity confirmation information for the item of the owner of the partner terminal using the public key, calculate the response encrypted information, and transmit the calculated response encrypted information as a response, andthe sameness determination unit is configured to decrypt the response encrypted information and determines whether or not the identity confirmation information for the item of the owner of the terminal and the identity confirmation information for the item of the owner of the partner terminal match each other based on whether or not the decryption result matches the predetermined value.

3. The owner sameness confirmation system according to claim 1, wherein E, which is the homomorphic encryption, is homomorphic encryption in which E(M1)×E(M2)=E(M1+M2) is satisfied for unencrypted texts M1 and M2,the confirmation request unit is configured to transmit E(V1) as the encrypted information for identity confirmation information V1 of the owner of the terminal,the confirmation response unit is configured to generate a random number r for identity confirmation information V2 of the owner of the partner terminal and transmits E(V1)r×E(V2)−r as the response encrypted information as a response, andthe sameness determination unit is configured to determine whether or not V1 and V2 match each other based on whether or not the decryption result of the response encrypted information is 0, which is the predetermined value.

4. The owner sameness confirmation system according to claim 1, wherein E, which is the homomorphic encryption, is homomorphic encryption in which E(M1)×E(M2)=E(M1×M2) is satisfied for unencrypted texts M1 and M2,the confirmation request unit is configured to transmit E(V1) as the encrypted information for identity confirmation information V1 of the owner of the terminal,the confirmation response unit is configured to generate a random number r for identity confirmation information V2 of the owner of the partner terminal and transmit E(V1)r×E(V2)−r as the response encrypted information as a response, andthe sameness determination unit is configured to determine whether or not V1 and V2 match each other based on whether or not the decryption result of the response encrypted information is 1, which is the predetermined value.

5. The owner sameness confirmation system according to claim 1, wherein the confirmation request unit is configured to transmit the confirmation request message via the partner terminal to the authentication station server that issued the electronic certificate to the partner terminal, andthe confirmation response unit is configured to transmit the confirmation response message via the partner terminal to the terminal.

6. The owner sameness confirmation system according to claim 1, wherein a value of a key owner included in the electronic certificate issued to the terminal is identification information of the terminal that is unrelated to the identity confirmation information of the owner of the terminal.

7. The owner sameness confirmation system according to claim 1, wherein the confirmation request message transmitted by the terminal is signed using at least any one of a secret key corresponding to the electronic certificate and a secret key corresponding to a model number electronic certificate indicating a model number of the terminal.

8. An owner sameness confirmation method for an owner sameness confirmation system including a plurality of terminals and a plurality of authentication station servers, wherein each of the terminals includesa first storage unit configured to store identity confirmation information of an owner of the terminal,the method comprises:transmitting, by the terminal, a confirmation request message including encrypted information obtained by encrypting the identity confirmation information of the owner of the terminal using a public key for homomorphic encryption, an electronic certificate of a partner terminal that is a target of owner sameness confirmation, and the public key, to an authentication station server that issued the electronic certificate to the partner terminal,the authentication station server that issued the electronic certificate to the partner terminal includesa second storage unit configured to store the electronic certificate issued to the partner terminal and identity confirmation information of an owner of the partner terminal in association with each other, andthe method further comprises:executing, by the authentication station server, upon receiving the confirmation request message, acquiring the identity confirmation information of the owner of the partner terminal from the electronic certificate of the partner terminal, and transmitting a confirmation response message including response encrypted information, which is the result of calculating an encrypted text obtained by encrypting the identity confirmation information using the public key and the encrypted information through computation corresponding to the homomorphic encryption, as a response to the terminal, anddecrypting, by the terminal, the response encrypted information, and determining whether or not the identity confirmation information of the owner of the terminal and the identity confirmation information of the owner of the partner terminal match each other based on whether or not the decryption result matches a predetermined value.

9. The owner sameness confirmation method according to claim 8, wherein the identity confirmation information is constituted by one or more items, and the method further comprises:calculating, by the terminal, the encrypted information by encrypting the identity confirmation information for an item for confirming the sameness using the public key, the item being selected from among the one or more items, and transmits the item in a state of being included in the confirmation request message,generating, by the authentication station server, the encrypted text obtained by encrypting the identity confirmation information for the item of the owner of the partner terminal using the public key, calculates the response encrypted information, and transmits the calculated response encrypted information as a response, anddecrypting, by the terminal, the response encrypted information and determines whether or not the identity confirmation information for the item of the owner of the terminal and the identity confirmation information for the item of the owner of the partner terminal match each other based on whether or not the decryption result matches the predetermined value.

10. The owner sameness confirmation method according to claim 8, wherein E, which is the homomorphic encryption, is homomorphic encryption in which E(M1)×E(M2)=E(M1+M2) is satisfied for unencrypted texts M1 and M2, and the method further comprises:transmitting, by the terminal, E(V1) as the encrypted information for identity confirmation information V1 of the owner of the terminal,generating, by the authentication station server, a random number r for identity confirmation information V2 of the owner of the partner terminal and transmits E(V1)r×E(V2)−r as the response encrypted information as a response, anddetermining, by the terminal whether or not V1 and V2 match each other based on whether or not the decryption result of the response encrypted information is 0, which is the predetermined value.

11. The owner sameness confirmation method according to claim 8, wherein E, which is the homomorphic encryption, is homomorphic encryption in which E(M1)×E(M2)=E(M1×M2) is satisfied for unencrypted texts M1 and M2, and the method further comprises:transmitting, by the terminal, E(V1) as the encrypted information for identity confirmation information V1 of the owner of the terminal,generating, by the authentication station server, a random number r for identity confirmation information V2 of the owner of the partner terminal and transmits E(V1)r×E(V2)−r as the response encrypted information as a response, anddetermining, by the terminal, whether or not V1 and V2 match each other based on whether or not the decryption result of the response encrypted information is 1, which is the predetermined value.

12. The owner sameness confirmation method according to claim 8, further comprises: transmitting, by the terminal, the confirmation request message via the partner terminal to the authentication station server that issued the electronic certificate to the partner terminal, andtransmitting, by the authentication station server, the confirmation response message via the partner terminal to the terminal.

13. The owner sameness confirmation method according to claim 8, wherein a value of a key owner included in the electronic certificate issued to the terminal is identification information of the terminal that is unrelated to the identity confirmation information of the owner of the terminal.

14. The owner sameness confirmation method according to claim 8, wherein the confirmation request message transmitted by the terminal is signed using at least any one of a secret key corresponding to the electronic certificate and a secret key corresponding to a model number electronic certificate indicating a model number of the terminal.