Revocable hierarchical identity-based encryption over lattice for pay-TV systems
In case the subscriber's certificate may be expired or revealed, a revocable mechanism is needed in a dynamic pay-TV system. Considering the hierarchical structure in this system, a revocable hierarchical identity-based encryption (RHIBE) scheme is a better choice than other schemes. But the well-known RHIBE schemes are constructed on the bilinear pairings. In this paper, two efficient and practical schemes are issued on lattice. Our first scheme is secure against adaptive identity-time attacks in the random oracle (RO) model and the second is against selective identity-time attacks in standard model. The security of both schemes is reduced to the learning with errors (LWE) assumption. In particular, the proposed scheme's basis delegation algorithms are run in the fixed dimension and the ciphertexts are shorter than existing schemes. Both schemes are much more efficient than the known works in terms of computation cost and storage cost.