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

Abstract

It is an object to implement a functional proxy re-encryption scheme. A decryption devicetransmits to a re-encryption devicea decryption key k*which is generated by converting, using conversion information W, 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 ψwhich is generated by encrypting the conversion information Wwith one of attribute information x' and attribute information v′ corresponding to each other being set. The re-encryption devicegenerates a re-encrypted ciphertext CT, constituted by a ciphertext cwhich is generated by setting at least one of additional information H and additional information Θ corresponding to each other in a ciphertext cin which is set the other one of the attribute information x and the attribute information v, and a decryption key k*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*.