| 摘要 |
PROBLEM TO BE SOLVED: To provide a public key encrypting system that ensures agreement by receivers to supplementary information added to substantial information and control of access to the substantial information without entailing extra communication.SOLUTION: A public key encrypting system comprises setting-up units 11 and 21 that set common parameters and parameters for a decryptor's signing scheme; a key generator 22 that generates a secret key for signing use and a public key for signing use, receivers' secret keys including the secret key for signing use, and receivers' public keys including the public key for signing use; an encrypting unit 14 that encrypts a message, which is substantial information, into an encrypted statement by using the receivers' public keys and conditions which are supplementary information; and a signature decrypting unit 24 that generates a signature for the conditions by using the secret key for signing use, verifies legitimacy of the signature by using the public key for signing use, and decrypts the encrypted statement into a correct message or outputs a wrong value according to whether or not the signature is legitimate. |
