Adam Back wrote: > Another framework is to have players which will only play content with > certified copy marks (no need for them to be visible -- they could be > encoded in a logo in the corner of the screen). The copymark is a > signed hash of the content and the identity of the purchaser. > > This could be relatively robust, except that usually there is also a > provision for non-certified content -- home movies etc -- and then the > copy mark can be removed while still playing by converting the content > into the home movie format, which won't and can't be certified.
The other obvious weakness in such a scheme is that the player can be modified to ignore the result of the check - rather like defeating dongles, which have yet to exhibit any noticable resistance to crackers. Cheers, Ben. -- http://www.apache-ssl.org/ben.html "There is no limit to what a man can do or how far he can go if he doesn't mind who gets the credit." - Robert Woodruff --------------------------------------------------------------------- The Cryptography Mailing List Unsubscribe by sending "unsubscribe cryptography" to [EMAIL PROTECTED]