1. A method for decrypting an encrypted transport stream, comprising: receiving the encrypted transport stream over a content delivery network, wherein the encrypted transport stream is encrypted using a first control word that serves as an encryption/decryption key; receiving a variable control word over the content delivery network; mathematically constraining the variable control word to create a second 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.