Paper 2010/119

How to Construct Space Efficient Revocable IBE from Non-monotonic ABE

Huang Lin, Zhenfu Cao, Muxin Zhou, and Haojin Zhu

Abstract

Since there always exists some users whose private keys are stolen or expired in practice, it is important for identity based encryption (IBE) system to provide a solution for revocation. The current most efficient revocable IBE system has a private key of size $\mathcal{O}(\log n)$ and update information of size $\mathcal{O}(r \log(\frac{n}{r}))$ where $r$ is the number of revoked users. We describe a new revocable IBE systems where the private key only contains two group elements and the update information size is $\mathcal{O}(r)$. To our best knowledge, the proposed constructions serve as the most efficient revocable IBE constructions in terms of space cost. Besides, this construction also provides a generic methodology to transform a non-monotonic attribute based encryption into a revocable IBE scheme. This paper also demonstrates how the proposed method can be employed to present an efficient revocable hierarchical IBE scheme.