| 摘要 |
PROBLEM TO BE SOLVED: To surely prevent the illegality of a server and a user by performing either processing of encipher or decoding to data in which electronic watermark information is embedded. SOLUTION: A system 100 consists of many entities such as a terminal device 10 on the side of a server, a terminal device 20 on the side of a user and a terminal device on the side of a verification station. Each entity mutually exchanges digital data through a network. In such a system 100, data into which electronic watermark information is embedded are subjected to either processing of encipher or decoding. In the system 100, information about a primary cipher such as a system and a secret key is the information which is known only to the server, and information about a secondary cipher is the information that is known only to the user. However, between these ciphers, they have the property that the cipher is solved when decoding is performed, whichever is ciphered first. |
