Side-channel attacks allow the adversary to gain partial knowledge of the secret key when cryptographic protocols are implemented in real-world hardware. The goal of leakage resilient cryptography is to design cryptosystems that withstand such attacks. In the auxiliary input model, an adversary is allowed to see a 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 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 chosen message attacks when given any exponentially hard-to-invert function of the secret key. As a second contribution, we construct a signature scheme that achieves security for random messages assuming that the adversary is given a polynomial-time hard-to-invert function (where both the challenge as well as the signatures seen prior to that are computed on random messages). Here, polynomial hardness is required even when given the entire public key. We further show that such signature schemes readily give us auxiliary input secure identification schemes.
Bibliographical noteFunding Information:
Sebastian Faust: Received funding from the Marie Curie IEF/FP7 project GAPS, Grant Number: 626467.
Jesper Buus Nielsen: Supported by European Research Commission Starting Grant 279447. Supported by Danish Council for Independent Research Starting Grant 10-081612. The authors acknowledge support from the Danish National Research Foundation and The National Science Foundation of China (under the Grant 61061130540) for the Sino-Danish Center for the Theory of Interactive Computation, from the CFEM research center (supported by the Danish Strategic Research Council) within which part of this work was performed.
© 2015, International Association for Cryptologic Research.