Practical Hierarchical Identity Based Encryption and Signature schemes Without Random Oracles.
Man Ho Au, Joseph K. Liu, Tsz Hon Yuen, Duncan S. Wong · IACR Cryptology ePrint Archive · 2006
In this paper, we propose a Hierarchical Identity Based Encryption scheme that is proven secure under the strongest model of [5] directly, without relying on random oracles. The size of the ciphertext is a constant while the size of public parameters is independent to the number of bit representing an identity. It is the first in the literature to achieve such a high security level and space efficiency at the same time. In addition, we also propose the first Hierarchical Identity Based Signature scheme that is proven under the strongest model without relying on random oracles and using more standard q-SDH assumption. Similar to the proposed encryption scheme, the space complexity of the signature and public parameters are as efficient as the proposed encryption scheme.