Abstract: Dynamic varying of encrypting of a stream of data at an encryption unit based on data content is disclosed. The dynamic varying of the encrypting, which can be responsive to passage of a predefined number of units of physical data or passage of a predefined number of conceptual units of data, is accomplished by changing at least one encryption parameter over different portions of the data. The at least one encryption parameter can comprise one or more of an encryption key, an encryption granularity, an encryption density scale, an encryption density, an encryption delay, an encryption key update variable, and an encryption key update data trigger. The change in encryption parameter is signaled to a receiver's decryption unit and used by the decryption unit in decrypting the dynamically varied encrypted stream of data. The stream of data may comprise, e.g., MPEG compressed video or audio.

Abstract: Copy protection is provided at a mass storage device provided in or connected to a decoder for receiving digital transmissions of audio and video program material by virtual scrambling of blocks of data. Non-sequential storage locations for blocks of data are defined in accordance with a key and the file allocation table is encrypted and stored. Thus blocks of data remain intact and need not be decrypted upon playback, reducing processing time, while the program is effectively protected from reassembly without decryption of the file allocation table. The key(s) may be maintained internally within the decoder and need not be shared, thus avoiding a need for user identification and/or authentication. Software for encryption, including keys may be downloaded to the decoder through the same transmission link used for transmission of data files that may be encrypted in response to control signals or flags transmitted with data files to be protected.

Abstract: Two data streams derived from a transmitted data stream are remultiplexed with a coarser granularity for storage in data blocks which assure that corresponding portions of each of the two data streams are made available in the same data block. The data streams are buffered in queues from which sub-blocks are transferred as buffer sections having sizes corresponding to relative bit rates therein in the order the sub-blocks are filled, preferably using bytes to interrupt processing. Thus, the sub-blocks will be grouped into data blocks in accordance with the correspondence of the data streams such as the time correspondence of audio and video data. As applied to digital video data transmissions, a system time clock (STC) value is stored in a sub-block header and/or a data block header and, using a look-up table or other arrangement for estimating a storage location, a data block can be retrieved from storage in accordance with a target STC value.

Abstract: Data corrupted or lost in transmission over a lossy digital transmission link is replaced and/or omitted from data presented in connection with storage to and read out from a mass storage device. Different procedures are used to conceal artifacts corresponding to errored data based upon valid data preceding and following the error in a data stream and a size of the error.

Abstract: Apparatus, method and computer program product are provided for digitally processing an encrypted data stream scrambled, for example, according to content scrambling system (CSS) technology. This digital processing insures against communication of clear data within the computer system from a central processing unit (CPU) to any accessible structure, such as memory or a system bus. Descrambling of the (CSS) scrambled data stream occurs within a module executing on the CPU, which is followed by reencryption of the data prior to transfer from the CPU. By so processing the data, integrity of copyrighted material is maintained, while allowing for software descrambling of the CSS encrypted data stream. Various techniques for establishing the encryption/decryption algorithm pair employed are described. Decryption of the re-encrypted data can occur at a receiving software module and/or a receiving hardware device, such as a decoder.

Abstract: Apparatus, method and computer program product are provided for digitally processing an encrypted data stream scrambled, for example, according to content scrambling system (CSS) technology. This digital processing insures against communication of clear data within the computer system from a central processing unit (CPU) to any accessible structure, such as memory or a system bus. Descrambling of the (CSS) scrambled data stream occurs within a module executing on the CPU, which is followed by re-encryption of the data prior to transfer from the CPU. By so processing the data, integrity of copyrighted material is maintained, while allowing for software descrambling of the CSS encrypted data stream. Various techniques for establishing the encryption/decryption algorithm pair employed are described. Decryption of the re-encrypted data can occur at a receiving software module and/or a receiving hardware device, such as a decoder.