A new key establishment protocol and its application in pay-TV systems

A pay-TV consumer uses a decoder to access encrypted digital content. To this end, a decoder contains a chip capable of decrypting the content. The recently standardized K-LAD key establishment protocol can be used to secure the delivery of content decryption keys to the chip. This paper presents a new key establishment protocol. The paper shows how the new protocol can be applied in a pay-TV system, and provides a comparison of the properties of the new protocol and the K-LAD protocol. In particular, it is shown that the new protocol offers a similar level of security as the K-LAD protocol against attacks in which content decryption keys are compromised and re-distributed. An advantage of the new protocol compared to the K-LAD protocol is that the trusted third party in the new protocol manages a public master key of each decoder instead of a secret master key of each decoder. Compared to K-LAD, this simplifies key management and reduces the level of trust required in the trusted third party. In addition, the new protocol achieves the desirable property that a decoder needs to be revoked only if its chip is compromised. This reduces the risk that the decoder of an honest consumer needs to be revoked to restore system security.