| 摘要 |
PROBLEM TO BE SOLVED: To provide a re-encryption system that re-encrypts an encryption message destined to a certain user terminal into a cypher text which another user terminal is able to decrypt without decrypting on the way, and that is able to control browsing of a message by a message receiver per message sender and field of the message.SOLUTION: A user terminal 10-3 of a user C transmitting a message encrypts a message using an encryption key including a secret key of the user terminal 10-3, the identification ID of a user terminal 10-1, which is a communication opposite party of the user terminal 10-3, and the identification ID of a message field δ, and transmits the encryption message to a conversion server. The user terminal 10-1 receiving the message decrypts a re-encryption message generated by a conversion server 20 using a conversion key by using a decryption key including a secret key of the user terminal 10-1, the identification ID of the user terminal 10-3, which is a communication opposite party of the user terminal 10-1, the identification ID of the message field δ, and takes out the original message. |
