Encoder and encoding method for electronic watermark, decoder and decoding method for electronic watermark, encoding and decoding program for electronic watermark, and recording medium for recording such program

摘要

Disclosed is an encoder for forming electronic watermark information which allows detecting tampering of a digital content based on an electronic watermark embedded in the digital content, and limiting said tampered part. This encoder comprises means for dividing a subject digital content into multiple blocks, and means for independently forming the electronic watermark information in the individual blocks.