Novel secure communication protocol for conditional access system

A protocol for secure communication between set-top box and smart card in conditional access system is proposed. The proposed protocol uses the Schnorr identification scheme to achieve the authentication of smart card to set- top box and uses an asymmetric cryptosystem to achieve the authentication of set-top box to smart card. Both security and performance of the proposed protocol are analyzed and a comparison between the proposed proto- col and a previous protocol is provided. The result shows that the protocol is more secure at the cost of a little more computation spending and very applies to smart card with limited processing power. Moreover, the protocol makes it possible that various conditional access systems use the same set-top box because it is not necessary for set-top box to store any secret proprietary data of conditional access system in advance in the protocol.