CIPHERTEXT DECRYPTION RIGHT TRANSFER SYSTEM

摘要

PROBLEM TO BE SOLVED: To decrypt ciphertext generated using a certain public key, by using a private key different from a private key corresponding to the public key.;SOLUTION: A ciphertext decryption right transfer system is equipped with: an IBE private key generating means for generating a private key of an ID-based encryption system used for a decryption key transferred device on the basis of a main private key; an electronic sign means for generating an electronic signature based on the private key of the ID-based encryption system; an electronic signature verifying means for judging propriety of the electronic signature; a conversion key generating means for generating a conversion key for converting the ciphertext encrypted by the public key into ciphertext that can be decrypted by the private key of the ID-based encryption system, on the basis of a private key corresponding to the public key and the private key of the ID-based encryption system when the electronic signature verifying means has judged that the electronic signature is proper; and a ciphertext converting means for converting the ciphertext encrypted by the public key into ciphertext that can be decrypted by the private key of the ID-based encryption system.;COPYRIGHT: (C)2008,JPO&INPIT