A method for embedding digital watermark data in digital data contents
includes the steps of obtaining a frequency coefficient of block data of
digital data contents, obtaining a complexity of the block data, obtaining
an amount of transformation of the frequency coefficient from the
complexity and the digital watermark data, and embedding the digital
watermark data by transforming the frequency coefficient. In addition, a
method for reading digital watermark data includes the steps of
calculating a probability of reading `1` or `0` in a read bit sequence by
using a test method on the basis of binary distribution, determining the
presence or absence of digital watermark data according to the
probability, and reconstituting digital watermark data. Another method
includes the steps of performing soft decision in code theory by assigning
weights to the digital watermark sequence with a weighting function, and
reconstituting digital watermark data.
