METHOD AND DEVICE FOR PROVING PLAIN TEXT IDENTITY FOR PLURAL CRYPTOGRAMS, AND MEDIUM FOR RECORDING PROGRAM FOR PERFORMING PLAIN TEXT IDENTITY PROOF OF PLURAL CRYPTOGRAMS

摘要

PROBLEM TO BE SOLVED: To safely and efficiently enable the plane text identity of plural cryptograms to be proved without disclosing secret information between a certifier and an identifier by having the certifier prepare an information sequence for proving the identity of the plane text with regard to the plural cryptograms and having the identifier confirm only the identity without knowing the plain text. ;SOLUTION: A certifier prepares special plain texts and prepares a cryptogram from public information for enciphering with regard to the plain texts respectively. Moreover, an information system for indicating the identity of the plain text is prepared without letting the identifier know the plain text and discloses the information to the identifier. The identifier uses the public information corresponding to the information sequence and the cryptogram, and confirms the identity of the text. That is, when the cryptogram a user A (204a) prepares is transmitted to a user B (204b) in this system, an enciphering key for the cryptogram is enciphered by public keys of the user B (204b) of a receiver and of a center A (203a) of the identifier respectively, and the identity of the plain text (the enciphering key) for the two cryptograms is proved.;COPYRIGHT: (C)1999,JPO