Cryptology ePrint Archive: Report 2005/117

Boneh-Franklin Identity Based Encryption Revisited

David Galindo

Abstract: The first practical identity based encryption (IBE) scheme was proposed by Boneh and Franklin. In this work we point out that there is a flawed step in the security reduction exhibited by the authors. Fortunately, it is possible to fix it without changing the scheme or the underlying assumption. In the second place, we introduce a variant of the seminal IBE scheme which allows a more efficient security reduction. The new scheme is simpler, and has more compact ciphertexts than Boneh-Franklin's proposal, while keeping the computational cost. Finally, we observe that the flawed step pointed out here is present in several works, and that our techniques can be applied to obtain tighter reductions for previous relevant schemes.

Category / Keywords: public-key cryptography / provable security, identity-based encryption, exact security, bilinear maps

Publication Info: An extended abstract has been accepted for ICALP 2005.

Date: received 21 Apr 2005

Contact author: d galindo at cs ru nl

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Version: 20050421:170939 (All versions of this report)

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