2010 | OriginalPaper | Buchkapitel
Strong Cryptography from Weak Secrets
Building Efficient PKE and IBE from Distributed Passwords
verfasst von : Xavier Boyen, Céline Chevalier, Georg Fuchsbauer, David Pointcheval
Erschienen in: Progress in Cryptology – AFRICACRYPT 2010
Verlag: Springer Berlin Heidelberg
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Distributed-password public-key cryptography (DPwPKC) allows the members of a group of people, each one holding a small secret password only, to help a leader to perform the private operation, associated to a public-key cryptosystem. Abdalla
et al.
recently defined this tool [1], with a practical construction. Unfortunately, the latter applied to the ElGamal decryption only, and relied on the DDH assumption, excluding any recent pairing-based cryptosystems. In this paper, we extend their techniques to support, and exploit, pairing-based properties: we take advantage of pairing-friendly groups to obtain efficient (simulation-sound) zero-knowledge proofs, whose security relies on the Decisional Linear assumption. As a consequence, we provide efficient protocols, secure in the standard model, for ElGamal decryption as in [1], but also for Linear decryption, as well as extraction of several identity-based cryptosystems [6,4]. Furthermore, we strenghten their security model by suppressing the useless
testPwd
queries in the functionality.