Patent ID: 8687806

Claim:
A method for decrypting an encrypted transport stream, comprising: receiving the encrypted transport stream over a content delivery network, wherein the encrypted transport stream was encrypted using a first control word that serves as an encryption/decryption key; receiving a variable control word over the content delivery network; receiving a multiple bit fixed control word over a communication path that is different than the content delivery network; and processing the variable control word with the multiple bit fixed control word to create a mathematically constrained second control word, wherein a first plurality of bits of the second control word are equal to corresponding bits of the variable control word, and a second plurality of bits of the second control word are formed using bits of the fixed control word, and wherein the created second control word is mathematically constrained with respect to the variable control word; and decrypting the encrypted transport stream using the second control word if the second control word is the same as the first control word.