Patent ID: 7464266

Claim:
A method for signing frame transmissions from a broadcast server to a client device, comprising: obtaining a data block that is scheduled for transmission in a next frame; wherein the next frame includes segment groups; wherein each segment group includes a number (n) of data blocks; wherein each data block includes a plurality of packets; selecting a secret key (S n ) that is associated with the client device for a predetermined number of the data blocks in the frame; generating a count that is associated with a time; computing a set of hash keys using the secret key (S n ) and the count; selecting a hash key (S i ) that is associated with the data block, wherein the selected hash key corresponds to one of the set of hash keys; computing a keyed-hash message authentication code (HMAC) value for the next frame using the hash key (S 1 ); periodically signing and transmitting a datum containing the hash key of an earlier or initial frame with a digital signature key (K S ); and assembling the next frame such that the data block and the HMAC value appear before the hash key in the frame transmission.