| 摘要 |
PROBLEM TO BE SOLVED: To allow a decoder which receives re-encrypted sentence data to verify whose original encrypted sentence data is re-encrypted.SOLUTION: In a decoder 50, holding means previously holds a verification expression established when a part of re-encrypted sentence data used for a re-encryption system, a public key used for encryption processing of encrypted sentence data before the re-encrypted sentence data is re-encrypted, and a secret key which can decode the re-encrypted sentence data are substituted. Determining means substitutes a part of the re-encrypted sentence data received from a re-encryption device 40, a public key of a re-encryption key generation device 30, which is read from storage means, and a secret key of the decoder 50 for the verification expression, performs an operation on the basis of the verification expression which is read from the holding means, and determines whether the verification expression is established or not. Output means outputs verification success showing effect that the public key used for encryption processing of plain sentence data is the public key of the re-encryption key generation device 30 when the verification expression is established as the result of determination. |
