| 摘要 |
PROBLEM TO BE SOLVED: To prevent the surreptitious use or leakage of the data contents by embedding the supply data in the data contents to be supplied to a user as an electronic watermark and transferring the supply data after enciphering them by means of a cipher key. SOLUTION: The user data I1 are embedded in the data contents MO to be supplied to a user 1 as an electronic watermark at a data management center and used as the data contents M1. The data contents M1 are enciphered by means of a cipher key Ks1 and then supplied. The enciphered data contents are decoded by the key Ks1 and used. When the decoded data contents are stored, they are enciphered again by means of a cipher key Ks2. When the contents M1 are decoded and transferred to a user 2, the user data I2 on the user 2 are embedded in the contents M1 as an electronic watermark. Then the data I2 are supplied based on the scenario registered at the data management center after the data contents M2 where an electronic watermark is embedded are enciphered by another cipher key Ks3. |
