| 摘要 |
PROBLEM TO BE SOLVED: To surely prevent an illegal use of digital data and to decrease the amount of communication or calculation to be performed for preventing the illegal use. SOLUTION: This is an electronic papermarking system wherein a server performs a first processing for generating plural pieces of different electronic papermark information, a second processing for generating plural pieces of enciphered information by enciphering these plural pieces of information while using individual cryptographic keys for each piece, a third processing for generating plural enciphered cryptographic keys by enciphering these individual cryptographic keys by multiplying a random number and a fourth processing for transmitting the plural pieces of enciphered information and the plural enciphered cryptographic keys as mentioned above to a user, while a user performs a fifth processing for selecting one of the plural pieces of transmitted enciphered information or one of the plural enciphered cryptographic keys corresponding to the enciphered information. A safe and highly efficient system concerning the illegal distribution of digital data can be provided by multiplying the random number only to the partial cryptographic key when multiplying the random number to the individual cryptographic keys. |
