Patent ID: 8693682

Claim:
A method of encrypting a data stream, wherein the data stream comprises encoded packets of data, wherein the method comprises: encrypting, using a first cipher and a first initialization vector or a first stream cipher key, a first encoded packet of data having a first importance level to generate a first encrypted packet having the first importance level; encrypting, using a second cipher and a second initialization vector or a second stream cipher key, a second encoded packet of data having the first importance level to generate a second encrypted packet having the first importance level, wherein the second initialization vector or the second stream cipher key is formed from a predetermined number of bits from the first encrypted packet; and encrypting, using a third cipher and the second initialization vector or the second stream cipher key, a third encoded packet of data having a second, lower, importance level to generate a third encrypted packet having the second importance level, wherein the third encoded packet of data is associated with the first encoded packet of data; wherein the first, second, and third encoded packets are encoded with encoding dependencies that correspond to the importance levels of the first, second, and third encoded packets, such that decoding encoded packets having the second importance level requires a result of decoding an associated encoded packet having the first importance level, and such that encoded packets having the second importance level may be discarded without affecting the ability to decode encoded packets having the first importance level; and wherein the first, second, and third encrypted packets are encrypted with encryption dependencies that match the encoding dependencies of the corresponding encoded packets.