SIGNATURE DEVICE, SIGNATURE ENCRYPTION DEVICE, VERIFICATION DEVICE, DECODING DEVICE, RESTORATION DEVICE, INFORMATION PROVIDING DEVICE, COMMUNICATION SYSTEM, SIGNATURE METHOD, SIGNATURE ENCRYPTION METHOD, AND VERIFICATION METHOD

摘要

PROBLEM TO BE SOLVED: To surely verify the validity of signature target data.;SOLUTION: The signature device 14 is provided with a hash value generator 14c which generates a hash value (u), by inputting a verification key (vk) and an encrypted message (c) to a hash function H2; a signature information generator 14d which generates signature information (v) to the encrypted message (c) by using the hash value (u) and a random number (s) used for the encryption; and a signature part 14e for adding signature which includes the hash value (u) and the signature information (v), and the verification key (vk) to the encrypted message (c) of the signature target data.;COPYRIGHT: (C)2007,JPO&INPIT