Abstract: The invention provides a method of recovering from de-synchronization attacks includes registering original and altered digital content using nonlinear transformations to iteratively attempt to provide better-approximated registration. Approximation occurs at more than one level of granularity, by selecting among a greater number of possible transformation functions at each step. Transformations and comparisons might be conducted directly on pixel values, on coefficients for a set of basis wavelets, or on some transformation of the original and altered digital content. A human operator might assist this process, such as by suggesting transformations or providing evaluation of the degree of registration. Upon resynchronization, embedded identifying information in the original digital content is recovered.

Abstract: Secure presentation of media streams includes encoding the media streams into digital content, encrypting a portion of that digital content, the portion being required for presentation, in which the encrypted version is substantially unchanged in formatting parameters from the clear version of the digital content. Selecting those portions for encryption so there is no change in distribution of the media stream: packetization of the digital data, or synchronization of audio with video portions of the media stream. When encoding the media stream into MPEG-2, refraining from encrypting information by which the video block data is described, packet formatting information, and encrypting the video block data using a block-substitution cipher. A block-substitution cipher can be used to encrypt each sequence of 16 bytes of video data in each packet, possibly leaving as many as 15 bytes of video data in each packet in the clear.

Abstract: A technique of distributing digital content representing media streams, and keys for unlocking that content, to a user. Content is deliverable to the user separately from licenses to that content. Content is delivered encrypted. Licenses are delivered designating selected presentation devices owned by the user. The presentation devices include a secure portion, relatively resistant to tampering by the user, in which each presentation device maintains a unique presentation device key. The user owns one or more such presentation devices, coupled using a local communication link to a local library, which maintains a copy of the content in an encrypted form. The user can search the library for information generally available about the media stream.