JP2009267900A - Key generating device, certificate generating device, service providing system, key generating method, certificate generating method, service providing method, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To vary a key length to be used in accordance with a security level requested for a service by generating a plurality of public keys corresponding to a plurality of private keys from a single private key of a user and storing the public keys in a certificate. <P>SOLUTION: A master private key, that a user owns, and a key length (L bits) of a key desired to generate are inputted at least, information containing the inputted master private key and key length of the private key desired to generate is processed by a unidirectional function to generate a partial private key of (n) bits and by processing information containing the inputted master private key and key length of the private key desired to generate and the partial private key generated just before by means of a unidirectional function, a plurality (N pieces (N is a positive integer)) of partial private keys are generated. Then, the plurality of generated partial private keys are coupled to generate the private key having the key length (L=nN bits) of the private key desired to generate, and the generated private key is processed by a unidirectional function to generate a public key. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a key generation device, a certificate generation device, a key generation method, a certificate generation method, and a service provision system using the generated key and certificate, a service provision method, and a program.

  In recent years, various services using computers have been provided. In many services, various encryption methods are used to authenticate users and conceal data. For public key cryptography, which is a method of encryption, authenticates the owner of a public key and issues a public key certificate for use in digital signature and encryption of public key cryptography and signature technology. The standardization and practical use of the base (PKI) is progressing.

Here, for public key cryptography, at the time of key generation, the biometric information B of the user is obtained, the secret information R is obtained, and the secret key SK for the public key cryptography is generated using the biometric information B and the secret information R. Then, when authenticating the identity, the second biometric information B of the user is obtained with respect to the secret key SK in the RSA public key method generated using the secret information R and the first biometric information B of the user. The public key issued by the certificate authority by verifying that the secret key SK is generated from the secret information R and the first biometric information B using the second biometric information B A technique for increasing the reliability of a certificate is known (see, for example, Patent Document 1).
JP 2003-323116 A

  However, in general, safety and convenience are in a trade-off relationship, and one method is not necessarily suitable for all devices. In particular, since public key cryptography has a processing time that varies greatly depending on the key length, it is desirable to use a key of an appropriate length according to the required conditions. However, in existing PKI, a public key certificate must be issued in advance. Therefore, a public / private key pair with a fixed key length was always generated and used.

  Therefore, the present invention generates a plurality of public keys corresponding to a plurality of secret keys from a single secret key of the user, and stores the public keys in a certificate so as to match the security level required by the service. An object of the present invention is to provide a key generation device, a certificate generation device, a service provision system, a key generation method, a certificate generation method, a service provision method, and a program that can change the key length to be used.

  The present invention proposes the following items in order to solve the above-described problems.

  (1) According to the present invention, an input means for inputting at least a master secret key owned by a user and a key length (L bits) of a key to be generated, the input master secret key, and a key of the secret key to be generated The information including the length is processed with a one-way function to generate an n-bit partial secret key, and thereafter the information including the input master secret key and the key length of the secret key to be generated, And a partial secret key generating means for generating a plurality of (N: N is a positive integer) partial secret keys by processing the generated partial secret keys with a one-way function, and the generated plurality of partial secrets A secret key generating means for generating a secret key having a key length (L = nN bits) of the secret key to be generated by combining the keys, and generating the public key by processing the generated secret key with a one-way function And a public key generation means for generating the key It has proposed a location.

  According to the present invention, the input means inputs at least the master secret key owned by the user and the key length (L bits) of the key to be generated. The partial secret key generation unit generates an n-bit partial secret key by processing the information including the input master secret key and the key length of the secret key to be generated with a one-way function, and thereafter input The information including the master secret key, the key length of the secret key to be generated, and the partial secret key generated immediately before are processed with a one-way function to obtain a plurality of parts (N: N is a positive integer). Generate a secret key. The secret key generation unit combines the plurality of generated partial secret keys to generate a secret key having a key length (L = nN bits) of the secret key desired to be generated. The public key generation means generates a public key by processing the generated secret key with a one-way function. Therefore, the user manages only one master secret key, and the secret key normally used can be dynamically generated with an arbitrary key length.

  (2) In the key generation device according to (1), when a plurality of secret keys and public keys having the same key length are generated, an index number is input to the input unit. Has proposed.

  According to the present invention, when a plurality of secret keys and public keys having the same key length are generated, the index number is input to the input means. Therefore, even if the partial secret key is revealed to a third party, the master secret Key security can be maintained.

  (3) The present invention proposes a key generation device characterized in that the one-way function is a hash function for the key generation device of (1) or (2).

  According to this invention, since the one-way function is a hash function, high-speed arithmetic processing can be realized.

  (4) The present invention relates to the key generation device according to (1) or (2), wherein the input unit, the partial secret key generation unit, and the secret key generation unit are provided in a tamper resistant device. Has proposed.

  According to the present invention, since the input means, the partial secret key generation means, and the secret key generation means are provided in the tamper resistant device, high-speed encryption processing can be realized while protecting the master secret key.

  (5) The present invention hashes the public key input means for inputting the public key generated by the key generation apparatus of (2) to (4), and the certificate information held by the input public key and the certificate authority server. The hash value obtained by processing the hash value of each public key and the hash value of the certificate information by processing the function, and the hash value obtained by processing the certificate information held by the certificate authority server And a signature means for signing with the private key held by the certificate authority server by combining the calculated hash values of the public keys, and the public key certificate, the certificate information, the respective public keys, A certificate generation device is proposed, which includes a storage means for storing a hash value of the public key and a signature.

  According to this invention, the public key input means inputs the public key generated by the key generation device. The hash value calculation means processes the input public key with a hash function to calculate a hash value of each public key and a hash value of the certificate information. The signing means combines the hash value obtained by processing the certificate information held by the certificate authority server with a hash function and the calculated hash value of each public key, and uses the secret key held by the certificate authority server. Sign. The storage means stores the certificate information, each public key, the hash value of the public key, and the signature in the public key certificate. Accordingly, since the signature of the public key certificate is calculated with respect to a value obtained by concatenating the hash value of each public key and the hash value of other information, disclosure / non-disclosure of each public key can be controlled.

  (6) The present invention is a service providing system including a key generating device, a certificate generating device, and a service providing server operated by a service provider, wherein the key generating device includes a master secret key owned by a user, The information including at least the input means for inputting the key length (L bits) of the key to be generated, the input master secret key, and the key length of the secret key to be generated is processed by a one-way function, and n A bit partial secret key is generated, and thereafter, the information including the input master secret key, the key length of the secret key to be generated, and the partial secret key generated immediately before are processed with a one-way function. Then, a partial secret key generating means for generating a plurality of partial secret keys (N: N is a positive integer) and the generated plurality of partial secret keys are combined, and the key length of the secret key to be generated ( L = nN bits) private key And a public key generation unit that generates a public key by processing the generated secret key with a one-way function, and the certificate generation device authenticates the input public key and authentication Hash value calculation means for processing the certificate information held by the station server with a hash function to calculate the hash value of each public key and the hash value of the certificate information, and the certificate information held by the certificate authority server A signature means for signing with the private key held by the certificate authority server by combining the hash value obtained by processing the hash value with the hash function and the hash value of each calculated public key, and the public key certificate A storage means for storing the certificate information, each public key, a hash value of the public key, and a signature; and a public key certificate transmission means for transmitting the public key certificate to a user, and providing the service server Receiving means for receiving the public key certificate from the user, verification means for verifying the validity of the received public key certificate, and the service provider selecting a public key in accordance with the security level. Encryption means for encrypting data to be sent to the user with the selected public key, and data transmission means for sending the encrypted data and information on the selected public key to the user. A service providing system is proposed in which a secret key corresponding to a selected public key is generated from a master secret key, and data is decrypted with the generated secret key.

  According to this invention, the input means of the key generation device inputs at least the master secret key owned by the user and the key length (L bits) of the key to be generated. The partial secret key generation unit generates an n-bit partial secret key by processing the information including the input master secret key and the key length of the secret key to be generated with a one-way function, and thereafter input The information including the master secret key, the key length of the secret key to be generated, and the partial secret key generated immediately before are processed with a one-way function to obtain a plurality of parts (N: N is a positive integer). Generate a secret key. The secret key generation unit combines the plurality of generated partial secret keys to generate a secret key having a key length (L = nN bits) of the secret key desired to be generated. The public key generation means generates a public key by processing the generated secret key with a one-way function. The public key input means of the certificate generation device inputs the public key generated by the key generation device. The hash value calculation means processes the input public key and the certificate information held by the certificate authority server with a hash function, and calculates the hash value of each public key and the hash value of the certificate information. The signing means combines the hash value obtained by processing the certificate information held by the certificate authority server with a hash function and the calculated hash value of each public key, and uses the secret key held by the certificate authority server. Sign. The storage means stores the certificate information, each public key, the hash value of the public key, and the signature in the public key certificate. The receiving means of the service providing server receives a public key certificate from the user. The verification means verifies the validity of the received public key certificate. In the encryption means, the service provider selects a public key in accordance with the security level, and encrypts data to be sent to the user with the selected public key. The data transmission means transmits the encrypted data and the selected public key information to the user. Then, the user generates a secret key corresponding to the selected public key from the master secret key, and decrypts the data with the generated secret key. Therefore, efficient encryption processing can be realized by properly using a plurality of public keys and secret keys having different key lengths according to the required security level. Also, by using a plurality of public / private keys for each service, security can be enhanced and the signature level can be controlled.

  (7) The present invention provides a key generation method for generating a key used for providing a service with an arbitrary key length, and includes at least a master secret key owned by a user and a key length (L bits) of a key to be generated. The information including the input first step, the input master secret key, and the key length of the secret key to be generated is processed with a one-way function to generate an n-bit partial secret key. The input master secret key, information including the key length of the secret key to be generated, and the partial secret key generated immediately before are processed by a one-way function, and a plurality of (N: N is a positive integer) And a second step of generating a secret key having a key length (L = nN bits) of the secret key to be generated by combining the generated plurality of partial secret keys. And the generated secret key is processed with a one-way function. It proposes a key generation method characterized by comprising a fourth step of generating the public key, the Te.

  According to the present invention, at least the master secret key owned by the user and the key length (L bits) of the key to be generated are input, and the information including the input master secret key and the key length of the secret key to be generated Is processed with a one-way function to generate an n-bit partial secret key, and thereafter, the information including the input master secret key, the key length of the secret key to be generated, and the partial secret generated immediately before The keys are processed with a one-way function to generate a plurality (N: N is a positive integer) partial secret keys. Then, a plurality of generated partial secret keys are combined to generate a secret key having a key length (L = nN bits) of the secret key to be generated, and the generated secret key is processed by a one-way function to public key Is generated. Therefore, the user manages only one master secret key, and the secret key normally used can be dynamically generated with an arbitrary key length.

  (8) The present invention is a certificate generation method for generating a certificate based on the key generated in (7), wherein the first step of inputting the public key generated in (7); A second step of processing the input public key and certificate information held by the certificate authority server with a hash function to calculate a hash value of each public key and a hash value of the certificate information; A hash value obtained by processing the certificate information held by the server with a hash function and the calculated hash value of each public key are combined to sign with the private key held by the certificate authority server. And a fourth step of storing the certificate information, each public key, a hash value of the public key, and a signature in a public key certificate. is suggesting.

  According to this invention, the public key generated by the key generation device is input, the input public key and the certificate information held by the certificate authority server are processed by the hash function, and the hash value of each public key and Calculate the hash value of the certificate information. The certificate authority server combines the hash value obtained by processing the certificate information held by the hash function and the calculated hash value of each public key, and performs signature with the secret key held by the certificate authority server. Then, the certificate information, each public key, the hash value of the public key, and the signature are stored in the public key certificate. Accordingly, since the signature of the public key certificate is calculated with respect to a value obtained by concatenating the hash value of each public key and the hash value of other information, disclosure / non-disclosure of each public key can be controlled.

  (9) The present invention is a service providing method in a service providing system including a key generating device, a certificate generating device, and a service providing server operated by a service provider, and the key generating device is owned by a user. A first step of inputting at least a master secret key and a key length (L bits) of a key to be generated, and information including the input master secret key and the key length of the secret key to be generated. To generate an n-bit partial secret key, and thereafter, the information including the input master secret key, the key length of the secret key to be generated, and the partial secret key generated immediately before A second step of generating a plurality of partial secret keys (N: N is a positive integer) by processing with a one-way function and the generated plurality of partial secret keys are combined to generate the secret to be generated Key length ( = NN bits), a third step of generating a public key by processing the generated secret key with a one-way function, and the certificate generating apparatus A fifth step of processing the public key and the certificate information held by the certificate authority server with a hash function to calculate the hash value of each public key and the hash value of the certificate information, and the certificate authority server holds A sixth step of combining the hash value obtained by processing the certificate information with a hash function and the calculated hash value of each public key and signing with the secret key held by the certificate authority server; A seventh step of storing the certificate information, each public key, a hash value of the public key, and a signature in a public key certificate; an eighth step of transmitting the public key certificate to the user; Service delivery A server that receives the public key certificate from the user, a tenth step that verifies the validity of the received public key certificate, and that the service provider matches the security level. An eleventh step of selecting a public key and encrypting data to be sent to the user with the selected public key, and a twelfth step of transmitting the encrypted data and information on the selected public key to the user And a thirteenth step in which the user generates a secret key corresponding to the selected public key from the master secret key and decrypts the data with the generated secret key. Proposes a provision method.

  According to the present invention, the key generation device inputs at least the master secret key owned by the user and the key length (L bits) of the key to be generated, and the input master secret key and the key of the secret key to be generated The information including the length is processed with a one-way function to generate an n-bit partial secret key, and thereafter the information including the input master secret key and the key length of the secret key to be generated The generated partial secret key is processed by a one-way function to generate a plurality of (N: N is a positive integer) partial secret keys. Then, a plurality of generated partial secret keys are combined to generate a secret key having a key length (L = nN bits) of the secret key to be generated, and the generated secret key is processed by a one-way function to public key Is generated. On the other hand, the certificate generation device processes the input public key and the certificate information held by the certificate authority server with a hash function, calculates the hash value of each public key and the hash value of the certificate information, and performs authentication. The hash value obtained by processing the certificate information held by the station server with the hash function and the calculated hash value of each public key are combined, and the signature is signed with the private key held by the certificate authority server. Then, the certificate information, each public key, the hash value of the public key, and the signature are stored in the public key certificate, and the public key certificate is transmitted to the user. The service providing server receives the public key certificate from the user and verifies the validity of the received public key certificate. The service provider selects a public key in accordance with the security level, encrypts data to be sent to the user with the selected public key, transmits the encrypted data and information on the selected public key to the user, and The user generates a secret key corresponding to the selected public key from the master secret key, and decrypts the data using the generated secret key. Therefore, efficient encryption processing can be realized by properly using a plurality of public keys and secret keys having different key lengths according to the required security level. Also, by using a plurality of public / private keys for each service, security can be enhanced and the signature level can be controlled.

  (10) The present invention is a program for causing a computer to execute a key generation method for generating a key used for providing a service with an arbitrary key length, the master secret key owned by the user, and the key to be generated A first step of inputting at least a length (L bits), information including the inputted master secret key and the key length of the secret key to be generated by a one-way function, and an n-bit partial secret A key is generated, and thereafter, the input master secret key, information including the key length of the secret key to be generated, and the partial secret key generated immediately before are processed with a one-way function, and a plurality of A second step of generating a partial secret key (N: N is a positive integer) and a plurality of the generated partial secret keys are combined, and the key length of the secret key to be generated (L = nN bits) The third step to generate the private key And flop, proposes a program for executing a fourth step of generating a public key was treated with a one-way function private key thus generated, to the computer.

  According to the present invention, at least the master secret key owned by the user and the key length (L bits) of the key to be generated are input, and the information including the input master secret key and the key length of the secret key to be generated Is processed with a one-way function to generate an n-bit partial secret key, and thereafter, the information including the input master secret key, the key length of the secret key to be generated, and the partial secret generated immediately before The keys are processed with a one-way function to generate a plurality (N: N is a positive integer) partial secret keys. Then, a plurality of generated partial secret keys are combined to generate a secret key having a key length (L = nN bits) of the secret key to be generated, and the generated secret key is processed by a one-way function to public key Is generated. Therefore, the user manages only one master secret key, and the secret key normally used can be dynamically generated with an arbitrary key length.

  (11) The present invention is a program for causing a computer to execute a certificate generation method for generating a certificate based on the key generated in (7), wherein the public key generated in (7) is The first input step and the input public key and the certificate information held by the certificate authority server are processed by a hash function to calculate a hash value of each public key and a hash value of the certificate information. The certificate authority server holds the hash value obtained by processing the second step, the certificate information held by the certificate authority server with a hash function, and the calculated hash value of each public key. A third step of signing with a private key and a fourth step of storing the certificate information, each public key, the hash value of the public key, and the signature in a public key certificate are implemented in a computer. It has proposed a program for.

  According to this invention, the public key generated by the key generation device is input, the input public key and the certificate information held by the certificate authority server are processed by the hash function, and the hash value of each public key and Calculate the hash value of the certificate information. The certificate authority server combines the hash value obtained by processing the certificate information held by the hash function and the calculated hash value of each public key, and performs signature with the secret key held by the certificate authority server. Then, the certificate information, each public key, the hash value of the public key, and the signature are stored in the public key certificate. Accordingly, since the signature of the public key certificate is calculated with respect to a value obtained by concatenating the hash value of each public key and the hash value of other information, disclosure / non-disclosure of each public key can be controlled.

  (12) The present invention is a program for causing a computer to execute a service providing method in a service providing system including a key generating device, a certificate generating device, and a service providing server operated by a service provider, the key A first step in which the generation device inputs at least a master secret key owned by the user and a key length (L bits) of a key to be generated, the input master secret key, and a key length of the secret key to be generated And an n-bit partial secret key to generate an n-bit partial secret key. Thereafter, information including the input master secret key and the key length of the secret key to be generated, A second step of generating a plurality of (N: N is a positive integer) partial secret keys by processing the generated partial secret keys with a one-way function; and the generated plurality of partial secrets. A third step of combining the keys to generate a secret key having a key length (L = nN bits) of the secret key to be generated, and generating the public key by processing the generated secret key with a one-way function And the certificate generation device processes the input public key and the certificate information held by the certificate authority server with a hash function, and the hash value of each public key and the certificate information The hash value obtained by processing the certificate information held by the certificate authority server with a hash function and the calculated hash value of each public key, A sixth step of signing with a private key held by the certificate authority server; a seventh step of storing the certificate information, each public key, a hash value of the public key, and a signature in a public key certificate; , The public key certificate An eighth step of transmitting to the user; a ninth step of receiving the public key certificate from the user; and a tenth step of verifying the validity of the received public key certificate. An eleventh step in which the service provider selects a public key in accordance with the security level, and encrypts data to be sent to the user with the selected public key; and the encrypted data and the selection A twelfth step of transmitting the public key information to the user, and the user generates a secret key corresponding to the selected public key from the master secret key and decrypts the data using the generated secret key. A program for causing a computer to execute 13 steps is proposed.

  According to the present invention, the key generation device inputs at least the master secret key owned by the user and the key length (L bits) of the key to be generated, and the input master secret key and the key of the secret key to be generated The information including the length is processed with a one-way function to generate an n-bit partial secret key, and thereafter the information including the input master secret key and the key length of the secret key to be generated The generated partial secret key is processed by a one-way function to generate a plurality of (N: N is a positive integer) partial secret keys. Then, a plurality of generated partial secret keys are combined to generate a secret key having a key length (L = nN bits) of the secret key to be generated, and the generated secret key is processed by a one-way function to public key Is generated. On the other hand, the certificate generation device processes the input public key and the certificate information held by the certificate authority server with a hash function, calculates the hash value of each public key and the hash value of the certificate information, and performs authentication. The hash value obtained by processing the certificate information held by the station server with the hash function and the calculated hash value of each public key are combined, and the signature is signed with the private key held by the certificate authority server. Then, the certificate information, each public key, the hash value of the public key, and the signature are stored in the public key certificate, and the public key certificate is transmitted to the user. The service providing server receives the public key certificate from the user and verifies the validity of the received public key certificate. The service provider selects a public key in accordance with the security level, encrypts data to be sent to the user with the selected public key, transmits the encrypted data and information on the selected public key to the user, and The user generates a secret key corresponding to the selected public key from the master secret key, and decrypts the data using the generated secret key. Therefore, efficient encryption processing can be realized by properly using a plurality of public keys and secret keys having different key lengths according to the required security level. Also, by using a plurality of public / private keys for each service, security can be enhanced and the signature level can be controlled.

  According to the present invention, it is possible to perform cryptographic processing with an optimum key length in each service, and it is possible to improve convenience by reducing processing time and to take appropriate security measures.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Note that the constituent elements in the present embodiment can be appropriately replaced with existing constituent elements, and various variations including combinations with other existing constituent elements are possible. Therefore, the description of the present embodiment does not limit the contents of the invention described in the claims.

  The service providing system according to the present invention will be described in detail with reference to FIGS.

<Configuration of service provision system>
As shown in FIG. 1, the service providing system according to the present embodiment includes a key generating device 1, a certificate generating device 2, a certificate authority server 3, a user terminal 4, a service providing server 5, and a network 6. It is composed of

  The key generation device 1 dynamically generates a secret key having an arbitrary key length that is normally used from a master secret key managed by the user. The certificate generation device 2 stores a plurality of public keys generated by the key generation device 1 and hash values of the public keys, and also a plurality of public key authentication hash values generated by the key generation device 1 and the certificate authority server 3. The hash value of the certificate information held by the certificate authority server 3 is concatenated, the signature made with the private key held by the certificate authority server 3 is stored, and the certificate is generated.

  The certificate authority server 3 holds certificate information and a secret key used for signature. The user terminal 4 receives the public key certificate from the certificate generation device 2 and transmits the received public key certificate to the service providing server 5 via the network 6.

  The service providing server 5 receives the public key certificate from the user terminal 4 and verifies the validity of the received public key certificate. Then, according to the security level, the public key is selected, the data to be sent to the user terminal 4 is encrypted with the selected public key, and the encrypted data and the information on the selected public key are transmitted to the user.

<Configuration of key generation device>
The configuration of the key generation apparatus according to this embodiment will be described with reference to FIG.
As shown in FIG. 2, the key generation apparatus according to the present embodiment includes an input unit 11, a partial secret key generation unit 12, a secret key generation unit 13, and a public key generation unit 14.

  The input unit 11 inputs a master secret key owned by the user, a key length (L bits) of the key to be generated, and an index value. The partial secret key generation unit 12 processes the input master secret key, the key length of the secret key to be generated, and the index value with a hash function to generate an n-bit partial secret key. A plurality of (N: N is a positive integer) partial secrets by processing the generated master secret key, the key length of the secret key to be generated, the index value, and the partial secret key generated immediately before with a hash function Generate a key.

  Since the secret key dynamic generation process is composed of only a hash function, a high-speed calculation can be realized. Further, if the input unit 11, the partial secret key generation unit 12, and the secret key generation unit 13 are stored in the tamper resistant device, high-speed encryption processing can be realized while protecting the master secret key.

  The secret key generation unit 13 combines the plurality of partial secret keys generated in the partial secret key generation unit 12 to generate a secret key having a key length (L = nN bits) of the secret key to be generated. The public key generation unit 14 generates a public key by processing the generated secret key with a one-way function. The generated public key is transmitted to the certificate generating device 2.

<Configuration of certificate generator>
The configuration of the certificate generation device according to the present embodiment will be described with reference to FIG.
As shown in FIG. 3, the certificate generation apparatus according to the present embodiment includes hash value calculation units 21 a, 21 b, 21 c and a signature unit 22.

  The hash value calculation units 21a, 21b, and 21c process the public key input from the key generation device and the certificate information held by the certificate authority server 3 using a hash function, and the hash value and certificate information of each public key Calculate the hash value of. The process for calculating the hash value may be executed by the certificate authority server 3.

  The signature unit 22 combines the hash value obtained by processing the certificate information held by the certificate authority server with a hash function and the calculated hash value of each public key, and uses the secret key held by the certificate authority server. Sign. Note that the certificate generation apparatus transmits these pieces of information in order to store the certificate information, each public key, the hash value of the public key, and the signature in the public key certificate held by the certificate authority server 3.

<Configuration of service providing server>
The configuration of the service providing server according to the present embodiment will be described with reference to FIG.
As shown in FIG. 4, the service providing server according to the present embodiment includes a receiving unit 31, a verification unit 32, an encryption unit 33, and a transmission unit 34.

  The receiving unit 31 receives a public key certificate from the user terminal 4. The verification unit 32 verifies the validity of the received public key certificate. The encryption unit 33 selects a public key according to the security level by the service provider, and encrypts data to be sent to the user with the selected public key. The transmission unit 34 transmits the encrypted data and the selected public key information to the user.

<Processing of key generation device>
The process of the key generation device according to this embodiment will be described with reference to FIG.
First, at least a master secret key owned by the user and a key length (L bits) of a key to be generated are input (step S101), and information including the input master secret key and the key length of the secret key to be generated is input. On the other hand, an n-bit partial secret key is generated by processing with a propensity function, and thereafter, information including the input master secret key, the key length of the secret key to be generated, and the partial secret key generated immediately before Are processed by a one-way function to generate a plurality of (N: N is a positive integer) partial secret keys (step S102).

  A plurality of generated partial secret keys are combined to generate a secret key having a key length (L = nN bits) of the secret key to be generated (step S103), and the generated secret key is processed with a one-way function. A public key is generated (step S104).

  Therefore, the user manages only one master secret key, and the secret key normally used can be dynamically generated with an arbitrary key length.

<Processing of certificate generation device>
The process of the certificate generation apparatus according to this embodiment will be described with reference to FIG.
First, the public key generated by the key generation device is input (step S201), the input public key and the certificate information held by the certificate authority server are processed by a hash function, and the hash value of each public key and A hash value of the certificate information is calculated (step S202).

  Combine the hash value obtained by processing the certificate information held by the certificate authority server with a hash function and the calculated hash value of each public key, and sign with the private key held by the certificate authority server (step In step S203, the certificate information, each public key, the hash value of the public key, and the signature are stored in the public key certificate (step S204).

  Accordingly, since the signature of the public key certificate is calculated with respect to a value obtained by concatenating the hash value of each public key and the hash value of other information, disclosure / non-disclosure of each public key can be controlled.

<Processing of service providing system>
The process of the service providing system according to the present embodiment will be described using FIG.
First, the key generation device inputs at least the master secret key owned by the user and the key length (L bits) of the key to be generated (step S301), and the input master secret key and the key of the secret key to be generated The information including the length is processed with a one-way function to generate an n-bit partial secret key, and thereafter the information including the input master secret key and the key length of the secret key to be generated The generated partial secret key is processed with a one-way function to generate a plurality (N: N is a positive integer) partial secret keys (step S302).

  Then, a plurality of generated partial secret keys are combined to generate a secret key having the key length (L = nN bits) of the secret key to be generated (step S303). Then, the generated secret key is processed with a one-way function to generate a public key (step S304).

  The certificate generation device processes the input public key and the certificate information held by the certificate authority server with a hash function, and calculates the hash value of each public key and the hash value of the certificate information (step S305). Then, the hash value obtained by processing the certificate information held by the certificate authority server with the hash function and the calculated hash value of each public key are combined and signed with the private key held by the certificate authority server ( Step S306). Then, the certificate information, each public key, the hash value of the public key, and the signature are stored in the public key certificate (step S307), and the public key certificate is transmitted to the user (step S308).

  The service providing server receives the public key certificate from the user (step S309), and verifies the validity of the received public key certificate (step S310). Then, the service provider selects a public key in accordance with the security level, encrypts data to be sent to the user with the selected public key (step S311), and stores the encrypted data and the information on the selected public key. (Step S312).

  The user generates a secret key corresponding to the selected public key from the master secret key, and decrypts the data using the generated secret key (step S313).

  Therefore, efficient encryption processing can be realized by properly using a plurality of public keys and secret keys having different key lengths according to the required security level. Also, by using a plurality of public / private keys for each service, security can be enhanced and the signature level can be controlled.

  The processing of the key generation device, certificate generation device, and service providing system is recorded on a computer-readable recording medium, and the program recorded on this recording medium is read into the key generation device, certificate generation device, and service providing system. The key generation device, certificate generation device, and service providing system of the present invention can be realized by executing. The computer system here includes an OS and hardware such as peripheral devices.

  Further, the “computer system” includes a homepage providing environment (or display environment) if a WWW (World Wide Web) system is used. The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line.

  The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, and what is called a difference file (difference program) may be sufficient.

  The embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to the embodiments, and includes designs and the like that do not depart from the gist of the present invention.

It is a block diagram of the service provision system which concerns on this embodiment. It is a block diagram of the key generation apparatus which concerns on this embodiment. It is a block diagram of the certificate generation apparatus which concerns on this embodiment. It is a block diagram of the service provision server which concerns on this embodiment. It is a processing flow of the key generation apparatus which concerns on this embodiment. It is a processing flow of the certificate generation apparatus which concerns on this embodiment. It is a processing flow of the service provision server which concerns on this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Key generation apparatus 2 ... Certificate generation apparatus 3 ... Certificate authority server 4 ... User terminal 5 ... Service provision server 6 ... Network 11 ... Input part 12 ... Partial secret key generation unit 13 ... Secret key generation unit 14 ... Public key generation unit 21a, 21b, 21c ... Hash value calculation unit 22 ... Signature unit 31 ... Reception unit 32 ... Verification Unit 33 ... encryption unit 34 ... transmission unit

Claims (12)

An input means for inputting at least the master secret key owned by the user and the key length (L bits) of the key to be generated;
The information including the input master secret key and the key length of the secret key to be generated is processed by a one-way function to generate an n-bit partial secret key. Thereafter, the input master secret key and Then, a plurality of (N: N is a positive integer) partial secret keys are generated by processing the information including the key length of the secret key to be generated and the partial secret key generated immediately before with a one-way function. A partial secret key generation means;
A secret key generating means for combining the plurality of generated partial secret keys and generating a secret key having a key length (L = nN bits) of the secret key to be generated;
Public key generating means for processing the generated secret key with a one-way function to generate a public key;
A key generation device comprising:   The key generation apparatus according to claim 1, wherein when a plurality of secret keys and public keys having the same key length are generated, an index number is input to the input means.   The key generation apparatus according to claim 1, wherein the one-way function is a hash function.   The key generation apparatus according to claim 1, wherein the input unit, the partial secret key generation unit, and the secret key generation unit are provided in a tamper resistant device. Public key input means for inputting a public key generated by the key generation device according to claim 1;
Hash value calculation means for processing the input public key and certificate information held by the certificate authority server with a hash function, and calculating a hash value of each public key and a hash value of the certificate information;
The hash value obtained by processing the certificate information held by the certificate authority server with a hash function and the calculated hash value of each public key are combined, and the signature is signed with the private key held by the certificate authority server. Signing means;
Storage means for storing the certificate information, each public key, a hash value of the public key, and a signature in a public key certificate;
A certificate generation device comprising: A service providing system comprising a key generating device, a certificate generating device, and a service providing server operated by a service provider,
The key generation device is
An input means for inputting at least the master secret key owned by the user and the key length (L bits) of the key to be generated;
The information including the input master secret key and the key length of the secret key to be generated is processed by a one-way function to generate an n-bit partial secret key. Thereafter, the input master secret key and Then, a plurality of (N: N is a positive integer) partial secret keys are generated by processing the information including the key length of the secret key to be generated and the partial secret key generated immediately before with a one-way function. A partial secret key generation means;
A secret key generating means for combining the plurality of generated partial secret keys and generating a secret key having a key length (L = nN bits) of the secret key to be generated;
Public key generating means for processing the generated secret key with a one-way function to generate a public key;
With
The certificate generating device is
Hash value calculation means for processing the input public key and certificate information held by the certificate authority server with a hash function, and calculating a hash value of each public key and a hash value of the certificate information;
The hash value obtained by processing the certificate information held by the certificate authority server with a hash function and the calculated hash value of each public key are combined, and the signature is signed with the private key held by the certificate authority server. Signing means;
Storage means for storing the certificate information, each public key, a hash value of the public key, and a signature in a public key certificate;
Public key certificate transmission means for transmitting the public key certificate to the user;
With
The service providing server is
Receiving means for receiving the public key certificate from the user;
Verification means for verifying the validity of the received public key certificate;
The service provider selects a public key in accordance with the security level, and encrypts data to be sent to the user with the selected public key;
Data transmitting means for transmitting the encrypted data and the information of the selected public key to a user;
With
The service providing system, wherein the user generates a secret key corresponding to the selected public key from the master secret key, and decrypts the data using the generated secret key. A key generation method for generating a key used for providing a service with an arbitrary key length,
A first step of inputting at least a master secret key owned by a user and a key length (L bits) of a key to be generated;
The information including the input master secret key and the key length of the secret key to be generated is processed by a one-way function to generate an n-bit partial secret key. Thereafter, the input master secret key and Then, a plurality of (N: N is a positive integer) partial secret keys are generated by processing the information including the key length of the secret key to be generated and the partial secret key generated immediately before with a one-way function. A second step;
A third step of generating a secret key having a key length (L = nN bits) of the secret key to be generated by combining the plurality of generated partial secret keys;
A fourth step of processing the generated secret key with a one-way function to generate a public key;
A key generation method comprising: A certificate generation method for generating a certificate based on the key generated by the claim 7,
A first step of inputting a public key generated according to claim 7;
A second step of processing the input public key and certificate information held by the certificate authority server with a hash function to calculate a hash value of each public key and a hash value of the certificate information;
The hash value obtained by processing the certificate information held by the certificate authority server with a hash function and the calculated hash value of each public key are combined, and the signature is signed with the private key held by the certificate authority server. A third step;
A fourth step of storing the certificate information, each public key, a hash value of the public key, and a signature in a public key certificate;
A certificate generation method characterized by comprising: A service providing method in a service providing system comprising a key generating device, a certificate generating device, and a service providing server operated by a service provider,
A first step in which the key generation device inputs at least a master secret key owned by a user and a key length (L bits) of a key to be generated;
The information including the input master secret key and the key length of the secret key to be generated is processed by a one-way function to generate an n-bit partial secret key. Thereafter, the input master secret key and Then, a plurality of (N: N is a positive integer) partial secret keys are generated by processing the information including the key length of the secret key to be generated and the partial secret key generated immediately before with a one-way function. A second step;
A third step of generating a secret key having a key length (L = nN bits) of the secret key to be generated by combining the plurality of generated partial secret keys;
A fourth step of processing the generated secret key with a one-way function to generate a public key;
The certificate generation device processes the input public key and the certificate information held by the certificate authority server with a hash function, and calculates a hash value of each public key and a hash value of the certificate information. 5 steps,
The hash value obtained by processing the certificate information held by the certificate authority server with a hash function and the calculated hash value of each public key are combined, and the signature is signed with the private key held by the certificate authority server. A sixth step;
A seventh step of storing the certificate information, each public key, a hash value of the public key, and a signature in a public key certificate;
An eighth step of transmitting the public key certificate to the user;
A ninth step in which the service providing server receives the public key certificate from the user;
A tenth step of verifying the validity of the received public key certificate;
An eleventh step in which the service provider selects a public key in accordance with a security level and encrypts data to be sent to a user with the selected public key;
A twelfth step of transmitting the encrypted data and the information of the selected public key to a user;
A thirteenth step in which the user generates a secret key corresponding to the selected public key from the master secret key, and decrypts the data with the generated secret key;
A service providing method comprising the steps of: A program for causing a computer to execute a key generation method for generating a key used for providing a service with an arbitrary key length,
A first step of inputting at least a master secret key owned by a user and a key length (L bits) of a key to be generated;
The information including the input master secret key and the key length of the secret key to be generated is processed by a one-way function to generate an n-bit partial secret key. Thereafter, the input master secret key and Then, a plurality of (N: N is a positive integer) partial secret keys are generated by processing the information including the key length of the secret key to be generated and the partial secret key generated immediately before with a one-way function. A second step;
A third step of generating a secret key having a key length (L = nN bits) of the secret key to be generated by combining the plurality of generated partial secret keys;
A fourth step of processing the generated secret key with a one-way function to generate a public key;
A program that causes a computer to execute. A program for causing a computer to execute a certificate generation method for generating a certificate based on the key generated according to claim 7,
A first step of inputting a public key generated according to claim 7;
A second step of processing the input public key and certificate information held by the certificate authority server with a hash function to calculate a hash value of each public key and a hash value of the certificate information;
The hash value obtained by processing the certificate information held by the certificate authority server with a hash function and the calculated hash value of each public key are combined, and the signature is signed with the private key held by the certificate authority server. A third step;
A fourth step of storing the certificate information, each public key, a hash value of the public key, and a signature in a public key certificate;
A program that causes a computer to execute. A program for causing a computer to execute a service providing method in a service providing system including a key generating device, a certificate generating device, and a service providing server operated by a service provider,
A first step in which the key generation device inputs at least a master secret key owned by a user and a key length (L bits) of a key to be generated;
The information including the input master secret key and the key length of the secret key to be generated is processed by a one-way function to generate an n-bit partial secret key. Thereafter, the input master secret key and Then, a plurality of (N: N is a positive integer) partial secret keys are generated by processing the information including the key length of the secret key to be generated and the partial secret key generated immediately before with a one-way function. A second step;
A third step of generating a secret key having a key length (L = nN bits) of the secret key to be generated by combining the plurality of generated partial secret keys;
A fourth step of processing the generated secret key with a one-way function to generate a public key;
The certificate generation device processes the input public key and the certificate information held by the certificate authority server with a hash function, and calculates a hash value of each public key and a hash value of the certificate information. 5 steps,
The hash value obtained by processing the certificate information held by the certificate authority server with a hash function and the calculated hash value of each public key are combined, and the signature is signed with the private key held by the certificate authority server. A sixth step;
A seventh step of storing the certificate information, each public key, a hash value of the public key, and a signature in a public key certificate;
An eighth step of transmitting the public key certificate to the user;
A ninth step in which the service providing server receives the public key certificate from the user;
A tenth step of verifying the validity of the received public key certificate;
An eleventh step in which the service provider selects a public key in accordance with a security level and encrypts data to be sent to a user with the selected public key;
A twelfth step of transmitting the encrypted data and the information of the selected public key to a user;
A thirteenth step in which the user generates a secret key corresponding to the selected public key from the master secret key, and decrypts the data with the generated secret key;
A program that causes a computer to execute.

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