A decoder excludes an encryption code or key from decrypted or non-decrypted program output data. Decrypted program representative data is generated from an input datastream containing encrypted program data and an associated encryption code. The encrypted program data is decrypted using the encryption...http://www.google.com/patents/US5878135?utm_source=gb-gplus-sharePatent US5878135 - Decoding system for processing encrypted broadcast, cable or satellite video data
