Secure communication between set-top box and smart card in DTV broadcasting

In digital television (DTV) broadcasting, service providers charge a subscribing fee by scrambling the program with conditional access system as well as control the illegal receiving of the charged program. A smart card is used to decrypt the control words and transfer them back to set-top box (STB) to descramble the scrambled program. Secure communication between STB and smart card is directly related with the benefit of service providers and the legal rights of users, while key exchange is the essential part of secure communication. In this paper, we propose a key exchange protocol for STB and smart card based on Schnorr´s digital signature protocol and one-way hash function. Our proposed protocol is dynamic, secure, mutual authenticated and lower computation. Moreover, the proposed protocol can prevent smart cloning and McCormac Hack problems.