Patent ID: 7395433

Claim:
A method of ensuring that a digital document is verifiable as being from a specific source, thereby rendering ownership protection for content of the digital document, the method comprising the steps of: (a) providing a watermark injector in the form of a watermark injection algorithm embodied in stored on a computer readable storage medium, the watermark injector operating to steganographically embed a watermark into the digital document whereby a key is employed in the embedding of such watermark; (b) providing a complementary watermark extractor in the form of a watermark extraction algorithm embodied in stored on a computer readable storage medium, the watermark extractor operating to reverse the watermark injector's steganographic embedding of a watermark by extracting such embedded watermark from the digital document; (c) injecting a digital watermark into the digital document using the watermark injector and a randomly selected key; (d) converting the watermark extractor into tamper-resistant software (TRS) form, whereby the TRS form of the watermark extractor is obscure and has a property of responding chaotically to modification; (e) publishing the TRS form of the watermark extractor; and, (f) registering the TRS form of the watermark extractor with a trusted third party, whereby the trusted third party validates that the TRS form of the watermark extractor correctly identifies watermarks injected using the watermark injector but does not identify a watermark in content of a digital document which either does not possess it or which was embedded with the watermark using a different injection algorithm and/or a different key; whereby in a legal proceeding, the owner of content of the digital document has available as evidence to prove such ownership, each of the following; (i) the prior publication of the TRS form of the watermark extractor; (ii) the third party validation of the correctness of the TRS form of the watermark extractor; and, (iii) an ability to provide in such legal proceeding a demonstration of the TRS form of the watermark extractor extracting the watermark from the content; and, without it being necessary to reveal the injection algorithm, the extraction algorithm, or the key used in embedding the watermark.