Patent ID: 8265271

Claim:
A method for encrypting an encoded scalable enhancement frame sent by a sender device via its communicating means to a receiver device over a communications network, said encoded scalable enhancement frame comprising a plurality of complementary streams ordered in term of quality level, each complementary stream corresponding to a combination of more than one scalability type, where a complementary stream of a lower quality level corresponds to a lower quality on each scalability type, said method comprising: generating, by the sender device, one random key corresponding to a key of the complementary stream of the higher quality level; getting, by the sender device, keys of the complementary streams of the lower quality levels by successively applying a one-way function to the random key, where the one-way function output is different for each scalability type; and sending, by the sender device, a key of a complementary stream corresponding to a quality level to the receiver device, said key permitting a receiver device to generate the keys of the complementary streams of the lower quality levels only, wherein in the getting the key, the random key (K M,T ) is slit into a number of part (L KM,T , R KM,T ) corresponding to the number of scalability types, and a subsequent key (K M-I, T-J ) is generated using the one-way function on each part successively (h M-I (L KM,T )|h T-J (R KM,T )).