Efficient and Secure Key Management for Conditional Access Systems

In Digital TV service, subscribers get the access of channels of their interest. In conditional access systems (CAS), Control Word is used to deliver the multimedia content to legitimate subscribers securely. In order to update the Control Word frequently, a large number of messages are exchanged in the conventional key distribution systems. This article analyzes the strengths and weaknesses of the existing key distribution protocols for CAS and presents an efficient key distribution protocol for CAS based on Elliptic Curve Cryptography. The proposed protocol minimizes the storage cost and communication cost of subscribers. In addition to this, the proposed protocol facilitates the unrestricted channel package composition and minimum communication cost on rekeying. The proposed protocol also provides perfect forward and backward secrecy. As a result, the proposed protocol is well suited for Pay-TV systems.