A method for embedding a watermark into content is disclosed. The content contains
content samples. The method including the steps of: receiving the content, creating
a continuous watermark sequence from the watermark, and for each content sample
in a first predetermined order: calculating a sample mean, calculating a sample
variance, and normalizing the content. Further steps include generating a set of
content coefficients from the content, generating a set of watermark coefficients
from the watermark sequence, embedding the watermark in the content by adjusting
the amplitude of the watermark coefficients so that the distortion between the
content coefficients and the associated watermark coefficients are minimized using
a secret mapping function, and outputting the content. The mapping functions may
be controlled by a key-dependent random sequence to protect the watermarks.
