METHOD AND APPARATUS FOR WATERMARKING DIGITAL BITSTREAMS

A signal is encoded, for example, perceptually and, during or after the perceptual coding process, a digital watermark is inserted into a quantized digital information signal resulting from the perceptual coding process in such a manner that its insertion is imperceptible to one later listening to, displaying or otherwise utilizing the information signal. Moreover, the digital watermark may be inserted in accordance with a key indicative of the location of the mark in the digitally encoded signal. The key may be protected with a trusted entity and distributed in such a manner as to be not detectable by a pirate. Consequently, the key may be utilized at watermarking apparatus that can be located anywhere in the distribution channel of a copyright protected work. The key may be embedded in a secure microprocessor of validating apparatus at a point of distribution or even at a point of sale. In this manner, when or after a digital bitstream is fixed in a medium of expression or broadcast, the watermark can be applied at the time of fixing in a copy, thus validating an original legitimate copy. For example, a compact disc recording may be validated at the point of sale as an authorized copy through watermarking (validating) apparatus according to the present invention or, at the time of broadcast over radio frequencies or distribution via the Internet, information may be watermarked. In this manner, even though a work may be pirated, further information may be included or otherwise indicated by the watermark to assist in, not only recognizing a pirated work and the original from which the pirate copy was produced, but the identity of the pirate who later makes an unauthorized copy of the original.