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 dev ice (300) transmits� to a re encryption device (400)� a decryption key (k) which has been converted using conversion information (W) 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 (?) which has been encrypted from the conversion information (W) 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 (c) and decryption key (k) as re encrypted text (CT)� said cipher text (c) being generated by setting at least one piece of additional information among pieces of corresponding additional information (H� T) in cipher text (c) 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) being generated by setting at least the other piece of additional information among the pieces of additional information (H� T) in the decryption key (k).