lcs preferably a robust forensic watermark is not accessible in any way to the consumer u2014 or to u201c information pirates u201d a forensic watermark may be secured by a symmetric key held only by the seller a transaction id may be embedded at the time of purchase with a hash matching the symmetric key the watermark is then embedded using a very low density insertion mask lt 10 making it very difficult to find without the symmetric key retrieval of such a watermark is not limited by real time low cost constraints the recovery will typically only be attempted on known pirated material or material which is suspected of piracy a recovery time of 2 hours on a 400 mhz pc may therefore be reasonable the system of the present invention contemplates the need for updating and replacing previously embedded watermarks which may be thought of generally as u201c renewing u201d a watermark if someone is able to obtain the algorithms used to embed a watermark u2014 or is otherwise able to crack the security it would be desirable to be able to embed a new watermark using a secure algorithm new watermarks however cannot be implemented with complete success over night and thus there inevitably will be transition periods where older spcs are operating without updated software in such a transition period the content must continue to be.