Key transport protocol based on secret sharing: an application to conditional access systems

In today’s digital world, multimedia content is delivered to homes via the Internet, satellite, terrestrial and cable networks. Scrambling is a common approach used by conditional access systems to prevent unauthorized access to audio/visual data. The descrambling keys are securely distributed to the receivers in the same transmission channel. Their protection is an important part of the key management problem. Although public-key cryptography provides a viable solution, alternative methods are sought for economy and efficiency. This paper presents a key transport protocol based on secret sharing. It eliminates the need for a cipher, yet combines the advantages of symmetric and public-key ciphers.