Signing key obfuscation system signature key obfuscation method, encrypted using the signature key that is obfuscated signature system, encrypted signature method and a program using the signature key that is obfuscated

摘要

PROBLEM TO BE SOLVED: To provide a cryptographic signature technique using an obfuscated signature key that is based on a standard cryptological hypothesis and in which the size of a verification key is independent of the size of a security parameter.;SOLUTION: Using Waters09 signature, and further, using additive homomorphism of a cryptographic scheme for a power-calculation makes it possible to obfuscate even a complex signature structure. Further, for a verification-enabled encrypted signature, another scheme is applied to a cryptographic system used internally in the verification-enabled encrypted signature and to a cryptographic system used for encrypting the verification-enabled encrypted signature itself, and further, the scheme allows combination.;COPYRIGHT: (C)2013,JPO&INPIT