| 摘要 |
PROBLEM TO BE SOLVED: To provide a proxy re-encryption system, at least one of convenience and safety of which is enhanced.SOLUTION: A universal re-encryption key generation device 700 generates a universal re-encryption key urk, by converting a user private key skso that an original cipher text oct, that can be decrypted by the user private key sk, cannot be decrypted. A re-encryption key generation device 300 generates a re-encryption key rkfor changing the decodable range of a cipher text, that can be decrypted by the user private key sk, and in which the information indicating the decodable range of the cipher text is set, from the universal re-encryption key urk, without using the user private key skand a master secret key msk.SELECTED DRAWING: Figure 1 |
