## CryptoDB

### Paper: The Exact Security of an Identity Based Signature and its Applications

Authors: Benoît Libert Jean-Jacques Quisquater URL: http://eprint.iacr.org/2004/102 Search ePrint Search Google This paper first positively answers the previously open question of whether it was possible to obtain an optimal security reduction for an identity based signature (IBS) under a reasonable computational assumption. We revisit the Sakai-Ogishi-Kasahara IBS that was recently proven secure by Bellare, Namprempre and Neven through a general framework applying to a large family of schemes. We show that their modified SOK-IBS scheme can be viewed as a one-level instantiation of Gentry and Silverberg's alternative hierarchical IBS the exact security of which was never considered before. We also show that this signature is as secure as the one-more Diffie-Hellman problem. As an application, we propose a modification of Boyen's "Swiss Army Knife" identity based signature encryption (IBSE) that presents better security reductions and satisfies the same strong security requirements with a similar efficiency.
##### BibTeX
@misc{eprint-2004-12075,
title={The Exact Security of an Identity Based Signature and its Applications},
booktitle={IACR Eprint archive},
keywords={ID-based cryptography, signatures, provable security, exact security},
url={http://eprint.iacr.org/2004/102},
note={ libert@dice.ucl.ac.be 12562 received 2 May 2004, last revised 24 May 2004},
author={Benoît Libert and Jean-Jacques Quisquater},
year=2004
}