An Efficient Group Key Transport Protocol

Conditional access system offers different services to the many groups simultaneously. The broadcast contents are scrambled with the secret key that protects it from unauthorized users. The secret key is distributed by server to the authorized users and shared it between user and server. The key transport protocol is used to transfer the secret key securely to these users. In this paper we present an efficient group key transport protocol using Chinese remainder theorem for access control. In this protocol, user has to carry only two secret numbers or keys. The decoding of broadcast message is done by only one modular division and one decryption. The main advantage of our scheme is that, a server can update the scrambling key or group key in one message, without changing user’s key. The proposed protocol can be used for multiple group control, which is generally useful in Pay TV. Updating process of the group key does not increase communication and computation overhead on user as well as the server.