A novel protocol for downloadable CAS

This paper presents a novel protocol for downloadable conditional access system (DCAS) which can securely download conditional access (CA) software via bidirectional communication channel. The proposed DCAS protocol uses pre-assigned keys and certificates for mutual authentication between a DCAS headend and DCAS host, and then it shares a session key for encrypting and decrypting CA software to be downloaded to a DCAS host. In order to verify the stability and effectiveness of the proposed protocol, we implement the DCAS protocol simulator. It can emulate the function of DCAS entities and the process of messages for mutual authentication, session key sharing and code downloading. Finally, experimental results indicate that the proposed protocol satisfies the design requirements for DCAS¹.