Cryptographic system, re-encryption key generation device, re-encryption device, cryptographic method, and cryptographic program

摘要

It is an object to implement a functional proxy re-encryption scheme. A decryption device 300 transmits to a re-encryption device 400 a decryption key k*^rk which is generated by converting, using conversion information W₁, a decryption key k* in which is set one of attribute information x and attribute information v corresponding to each other, and encrypted conversion information ψ^rk which is generated by encrypting the conversion information W₁ with one of attribute information x′ and attribute information v′ corresponding to each other being set. The re-encryption device 400 generates a re-encrypted ciphertext CT, constituted by a ciphertext c^renc which is generated by setting at least one of additional information H and additional information Θ corresponding to each other in a ciphertext c^enc in which is set the other one of the attribute information x and the attribute information v, and a decryption key k*^renc which is generated by setting at least the other one of the additional information H and the additional information Θ in the decryption key k*^rk.