## Cryptology ePrint Archive: Report 2010/119

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

Huang Lin and Zhenfu Cao and 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.

Category / Keywords: public-key cryptography / Revocable IBE, Non-monotonic, Attribute based encryption

Date: received 4 Mar 2010, withdrawn 8 Mar 2010

Contact author: faustlin at sjtu edu cn

Available format(s): (-- withdrawn --)

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