CRYPTOGRAPHIC SYSTEM, ENCRYPTION DEVICE, RE-ENCRYPTION KEY GENERATION DEVICE, RE-ENCRYPTION DEVICE, AND CRYPTOGRAPHIC PROGRAM

摘要

An encryption device 200 outputs a ciphertext ct including a ciphertext c and a ciphertext c^˜. The ciphertext c has been set with one of attribute information x and attribute information v related to each other. The ciphertext c^˜ has been set with one of attribute information y and attribute information z related to each other. A decryption device 300 outputs a re-encryption key rk including a decryption key k*^rk, a decryption key k^˜*^rk, and encrypted conversion information φ^rk. The decryption key k*^rk is obtained by converting the decryption key k* which is set with the other one of attribute information x and attribute information v, with conversion information W_1,t. The decryption key k^˜*^rk has been set with the other one of the attribute information y and the attribute information z. The encrypted conversion information φ^rk is obtained by encrypting the conversion information W_1,t by setting one of attribute information x′ and attribute information v′ related to each other. A re-encryption device 400 outputs a re-ciphertext ret including a ciphertext c^renc and a decryption key k*^renc. The ciphertext c^renc is obtained by setting one of additional information H and additional information Θ to the ciphertext ct. The decryption key k*^renc is obtained by setting the other one of the additional information H and the additional information Θ to the re-encryption key rk.