| 摘要 |
PROBLEM TO BE SOLVED: To prevent a third party from pretending to be a signer in question. SOLUTION: A digital watermark generating part 15 reads signature information 6 from an encipherment processing part 13, and generates digital watermark information 8 of the signature information 6 based on the meaning of each digit. A digital watermark embedding processing part 17 reads the watermark information 8 and creates digital watermark embedded information for signature 10 by reading the watermark information 8 and embedding it in the information for signature 2 from an input part 1. The embedding of the watermark 8 in the objective information 2 is performed by using, for example, DCT or IDCT method. To prevent the signature information 6 from being easily read or separated from the information for signature 2, or to prevent another signature information from being illegally added to the information for signature 2, the embedding processing part 17 embeds the watermark information in plural distributed positions of the information for signature 2. The watermark information 8 is embedded by the embedding processing part 7 in plural positions determined at random in the information for signature 2, respectively. By these processes, it becomes possible to surely prevent a third party from pretending to be a signer in question. |
