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

摘要

The objective of the present invention is to achieve a proxy re-encryption method for functional encryption. A decryption device (300) transmits, to a re-encryption device (400), a decryption key (k*rk) which has been converted using conversion information (W1) from a decryption key (k*) in which one piece of attribute information among mutually corresponding pieces of attribute information (x and v) has been set, and encrypted conversion information (ψrk) which has been encrypted from the conversion information (W1) by setting one piece of attribute information among mutually corresponding pieces of attribute information (x' and v'). The re-encryption device (400) treats cipher-text (crenc) and decryption key (k*renc) as re-encrypted text (CT), said cipher-text (crenc) being generated by setting at least one piece of additional information among pieces of corresponding additional information (H, Θ) in cipher-text (cenc) in which the other piece of attribute information among the pieces of attribute information (x and v) has been set, and said decryption key (k*renc) being generated by setting at least the other piece of additional information among the pieces of additional information (H, Θ) in the decryption key (k*rk).