A Computationally Efficient and Scalable Key Management Scheme for Access Control of Media Delivery in Digital Pay-TV Systems

摘要

In today's Internet era, group communications in multimedia applications are becoming more and more popular. The issues of controlling illegal access to multimedia contents require efficient and secure mechanisms for distribution of common key called scrambling key or group key. In order to provide secure delivery of multimedia contents in digital pay-TV systems, a large number of keying information messages are exchanged for group key/scrambling key updates in the traditional key distribution schemes. In this paper we propose a Chinese Remainder Theorem (CRT) based key distribution protocol which is highly secure and computationally efficient. The proposed protocol, 1) has drastically reduced the computational complexity of Group Manager (GM) and members for updating the keys, 2) has greatly increased the security by using an additional secret parameter at Group Manager and members areas, 3) can efficiently handle large and dynamically updating groups and, 4) can update the group key in one message, without updating member's key. With our proposed key distribution scheme, only legal members can access the multimedia contents correctly and the illegal access can be prevented. The proposed scheme is applicable in Conditional Access System (CAS) of digital pay-TV systems without increasing storage and communication overheads on GM and members. The comparative analysis of our proposed scheme with existing schemes in terms of computational cost assures the effectiveness of our scheme. As a proof of concept, we implement our scheme to a decentralized architecture-based key management system and demonstrate that the proposed scheme significantly reduces the computational complexity.