Cryptology ePrint Archive: Report 2012/045

Signature Schemes Secure against Hard-to-Invert Leakage

Sebastian Faust and Carmit Hazay and Jesper Buus Nielsen and Peter Sebastian Nordholt and Angela Zottarel

Abstract: In the auxiliary input model an adversary is allowed to see a \emph{computationally hard-to-invert function} of the secret key. The auxiliary input model weakens the bounded leakage assumption commonly made in leakage resilient cryptography as the hard-to-invert function may information-theoretically reveal the entire secret key. In this work, we propose the \emph{first} constructions of digital signature schemes that are secure in the auxiliary input model. Our main contribution is a digital signature scheme that is secure against \emph{chosen message attacks} when given an \emph{exponentially hard-to-invert function} of the secret key. As a second contribution, we construct a signature scheme that achieves security for \emph{random messages} assuming that the adversary is given a \emph{polynomial-time} hard to invert function. Here, polynomial-hardness is required even when given the entire public-key -- so called \emph{weak} auxiliary input security. We show that such signature schemes readily give us auxiliary input secure identification schemes.

Category / Keywords: public-key cryptography / leakage, auxiliary input, signature

Date: received 30 Jan 2012

Contact author: psn at cs au dk

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Version: 20120201:040735 (All versions of this report)

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