AUTHENTICATED ENCRYPTION METHOD AND APPARATUS, AUTHENTICATED ENCRYPTION PROGRAM, MEMORY MEDIUM HAVING AUTHENTICATED ENCRYPTION PROGRAM STORED THEREON, AUTHENTICATED DECRYPTION METHOD AND APPARATUS, AUTHENTICATED DECRYPTION PROGRAM, MEMORY MEDIUM HAVING AUTHENTICATED DECRYPTION PROGRAM STORED THEREON, DENIAL CANCELLING METHOD, VERIFYING METHOD, VERIFIER AND VERIFICATION PROGRAM, AND MEMORY MEDIUM HAVING THE VERIFICATION PROGRAM STORED THEREON

摘要

PROBLEM TO BE SOLVED: To enable senders and receivers to deny communication contents with respect to a third person but will authorize a receiving person to conduct message authentication and to cancel the denial possibility of the sending person, as needed. SOLUTION: A redundant plain text m' is formed with a plain text m made redundant, a random number 4 is generated from short random number species s, a disturbant h is formed, a signatureσis given to h, and a set of m, r,σis encrypted and sent to a receiver. For verifying the plain text m and the signatureσabout an encryption text with its denial cancelled, the random number r is restored from the opened random number species s to form the redundant plain text m', and the disturbant h is formed from (r, IDb, m'), to verify if the signatureσis correct for the disturbant h, using a public key pks of the sender. COPYRIGHT: (C)2004,JPO