Secure Hierarchical Identity Based Encryption Scheme in the Standard Model

摘要

An identity based cryptosystem is a public key cryptosys-tem where the public key can be represented as an arbitrary string. Hierarchical identity based cryptography is a generalization of identity based encryption that mirrors an organizational hierarchy. It allows a root private key generator to distribute the workload by delegating private key generation and identity authentication to lower-level private key generators. Most of hierarchical identity based encryption schemes are provably secure in the random oracles or weak models without random oracles such as selective-ID model.rnCurrently, there is no hierarchical identity based encryption scheme that is fully CCA2 secure in the standard model, with short public parameters and a tight reduction. In this paper, we first propose a hierarchical identity based encryption scheme that is fully secure in the standard model. And it achieves IND-ID-CCA2 security based on the decision q-TBDHE problem. The ciphertext size is independent of the level of the hierarchy. Moreover, our scheme has short public parameters, high efficiency and a tight reduction simultaneously.