| Patent application number | Description | Published |
|---|
| 20080301449 | Signature Apparatus, Verifying Apparatus, Proving Apparatus, Encrypting Apparatus, and Decrypting Apparatus - Provided are a signature apparatus, a verifying apparatus, a proving apparatus, an encrypting apparatus, and a decrypting apparatus capable of efficiently reducing a signature text counterfeit problem to a discrete logarithm problem. The commitment is a hash value of a set of a value to be committed. Data including a pair of elements of a cyclic group associated with a discrete logarithm problem is used as a public key, and a discrete logarithm of an order of the pair is used as a secret key. Accordingly, it is possible to summarize secret information of an attacker from the commitment without rewinding the attacker and to ensure a higher safety than that of a Schnorr signature scheme. In addition, one-time power residue calculation is performed in each of the signature and verification calculations, so that it is possible to lower an amount of calculation in the signature and verification calculations. | 12-04-2008 |
| 20090034716 | TIME APPARATUS, ENCRYPTION APPARATUS, DECRYPTION APPARATUS, AND ENCRYPTION/DECRYPTION SYSTEM - A time apparatus subjects a plurality of IDs to extract algorism. Each of the plurality of IDs is configured from a bit sequence, and the bit sequence is formed by expressing a current time instant as a bit sequence and concatenating a few bits from the first of the bit sequence. The time apparatus produces a plurality of decryption keys obtained as a result of subjecting the plurality of specified IDs to the extract algorism. An encryption apparatus specifies a plurality of IDs. Each of the plurality of IDs is configured from a bit sequence, the bit sequence being formed by expressing the designated time instant as a bit sequence and concatenating a few bits from the first of the bit sequence. The encryption apparatus reads the encryption key and the plurality of IDs supplied from the time apparatus to encrypt same plaintext. The encryption apparatus produces plural pieces of ciphertext. A decryption apparatus selects one decryption key from the inputted plurality of decryption keys, and selects one ciphertext from the inputted plural pieces of ciphertext. The decryption section decrypts the selected ciphertext using the selected decryption key on the basis of an ID based encryption method. | 02-05-2009 |
| 20090034739 | KEY ISSUING METHOD, GROUP SIGNATURE SYSTEM, INFORMATION PROCESSING APPARATUS, AND PROGRAM - There is provided in accordance with the present invention a key issuing method for being performed by a user apparatus in a group signature system including the user apparatus and an issuer apparatus connected to the user apparatus through a network. The method comprises: reading an issuer public key from the issuer apparatus into a user storage through the network; receiving, from the issuer apparatus through the network, first confidential data including one or plural confidential texts which are produced by confidentializing the issuer public key using element data containing information of an element of a group in the issuer apparatus; performing a second confidential data generating process for generating second confidential data of a confidential text represented by the product of modulo-exponentiated element data corresponding to the confidential texts included in the first confidential data or a confidential text represented by the sum of the element data multiplied by a constant, using the issuer public key and the first confidential data; sending the second confidential data to the issuer apparatus through the network; receiving, from the issuer apparatus through the network, information generated in the issuer apparatus and based on the element data corresponding to the second confidential data; and generating a member public key which is a public key corresponding to the user apparatus and a member secret key which is a secret key corresponding to the user apparatus, using the information based on the element data corresponding to the second confidential data, and writing the member public key and the member secret key into the user storage. | 02-05-2009 |
| 20090041239 | PSEUDO-RANDOM FUNCTION CALCULATING DEVICE AND METHOD AND NUMBER-LIMITED ANONYMOUS AUTHENTICATION SYSTEM AND METHOD - An efficient pseudo-random function and an efficient limited number of times authentication system using such a function are realized. A pseudo-random function calculating device comprises a key creating means and a pseudo-random function calculating means. The key creating means creates a public key made of a set of at least a first component and a second component as components constituting an element of a finite group and a secret key made of an integer and secretly saves the created secret key in a secret key memory section but makes the public key public. The pseudo-random function calculating means outputs the element of a finite group as function value of the pseudo-random function upon receiving an integer as input. The pseudo-random function calculating means outputs the product of multiplication of the first element of the value obtained by calculating the modular exponentiation, using the first component of the public key and the input integer respectively as base and exponent, and the second element of the value obtained by calculating the modular exponentiation, using the second component of the public key and the reciprocal of the sum of the secret key and the input integer in a finite field respectively as base and component. | 02-12-2009 |
| 20090044017 | SIGNATURE AND VERIFYING METHOD, AND SIGNATURE AND VERIFYING DEVICE - An RSA signature method is provided in which the length of a signature does not depend on the number of signature devices when multiple signature devices are related to the creation of the signature. A signature device i_{m} includes first conversion means SS | 02-12-2009 |
| 20090271631 | ELECTRONIC SIGNATURE SYSTEM AND ELECTRONIC SIGNATURE VERIFYING METHOD - A key creating device creates a first public key and a first secret key of the electronic signature method satisfying the noncounterfeitability and a second public key and the first secret key of the chameleon commitment method. The signature device generates a commitment, a first random number according to the Com algorithm, and a first signature by using the first secret key. The signature device further generates a second random number according to the Cam algorithm by using the message written by adding a first signature to an object message, and creates an electronic signature by combining the first signature and the second random number. A verifying device receives the signed message written by adding the first signature included in the electronic signature to the object message, creates a commitment according to the ComVer algorithm, and performs verification by using the commitment and the first signature. | 10-29-2009 |
| 20090276630 | Group Signature System And Information Processing Method - In a group signature system of the present invention, user device | 11-05-2009 |
| 20100169643 | PROOF VERIFICATION SYSTEM, PROVING DEVICE, VERIFYING DEVICE, PROOF VERIFICATION METHOD, AND PROGRAM - The proof verification system of the present invention is composed of a proving device ( | 07-01-2010 |
| 20100251351 | INFORMATION AND COMMUNICATION SYSTEM, AN ORGANIZATION APPARATUS AND A USER APPARATUS - An information and communication system or the like which handles an attribute, at the same time enables the attribute not being made a public information, is efficient, and does not require a database should be provided. | 09-30-2010 |
