A detector (1) of signal detects an electronic watermark (first electronic
watermark) signal from an inputted contents data. The detected electronic watermark
signal is temporarily stored in a memory (2) for electronic watermark contents.
The temporary stored electronic watermark signal is transmitted to an inserter
(4) of electronic watermark signal. In the inserter (4), an electronic
watermark (second electronic watermark) signal of which content is equivalent to
the detected electronic watermark (first electronic watermark) signal is additionally
recorded in a contents signal, which is extracted by a extractor (3) of
contents signal.
