Cryptology ePrint Archive: Report 2009/084

Simulation without the Artificial Abort: Simplified Proof and Improved Concrete Security for Waters' IBE Scheme

Mihir Bellare and Thomas Ristenpart

Abstract: Waters' variant of the Boneh-Boyen IBE scheme is attractive because of its efficency, applications, and security attributes,but suffers from a relatively complex proof with poor concrete security. This is due in part to the proof's ``artificial abort'' step, which has then been inherited by numerous derivative works. It has often been asked whether this step is necessary. We show that it is not, providing a new proof that eliminates this step. The new proof is not only simpler than the original one but offers better concrete security for important ranges of the parameters. As a result, one can securely use smaller groups, resulting in significant efficiency improvements.

Category / Keywords: public-key cryptography / identity-based encryption

Publication Info: To appear at Eurocrypt 2009

Date: received 17 Feb 2009

Contact author: tristenp at cs ucsd edu

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Version: 20090224:095920 (All versions of this report)

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