Patent ID: 9338405
Filing Date: 2016-05-10
CPC Classification: H04N

Claim Text:
1. A method of decrypting a scrambled digital data item at a client, said method comprising: receiving a request at said client from a user to tune to a channel; receiving via a multicast or a broadcast television network, actual control messages at said client, wherein each actual control message comprises control word generating information for generating a control word associated with the actual control message; storing said actual control messages at said client; receiving, via a multicast or a broadcast television network, at said client, a portion of said scrambled digital data item after a tune point in said scrambled digital data item at which said user tuned to said channel, wherein said portion of said scrambled digital data item is received independently of said actual control messages; receiving a further request at said client from said user to rewind past the tune point; stopping the receiving of said portion of said scrambled digital data item while continuing to receive and store actual control messages; receiving, via a unicast, actual control messages associated with a previous portion of said scrambled digital data item prior to the tune point; receiving, via a unicast, said scrambled digital data item; and decrypting said scrambled digital data item received via unicast using said actual control messages associated with said previous portion and said actual control messages stored at said client; wherein said scrambled digital data item comprises a plurality of segments of scrambled digital data, each segment of scrambled digital data being associated with one of said actual control messages and being scrambled with the control word associated with said one of said actual control messages, and wherein said scrambled digital data item further comprises a plurality of reference control messages, each segment of scrambled digital data comprising one of said reference control messages, each of said reference control messages comprising a control message reference value identifying the actual control message associated with the segment of scrambled digital data.