, Volume 26, Issue 3, pp 513-558

Fully Leakage-Resilient Signatures

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A signature scheme is fully leakage resilient (Katz and Vaikuntanathan, ASIACRYPT’09) if it is existentially unforgeable under an adaptive chosen-message attack even in a setting where an adversary may obtain bounded (yet arbitrary) leakage information on all intermediate values that are used throughout the lifetime of the system. This is a strong and meaningful notion of security that captures a wide range of side-channel attacks.

One of the main challenges in constructing fully leakage-resilient signature schemes is dealing with leakage that may depend on the random bits used by the signing algorithm, and constructions of such schemes are known only in the random-oracle model. Moreover, even in the random-oracle model, known schemes are only resilient to leakage of less than half the length of their signing key.

In this paper we construct the first fully leakage-resilient signature schemes without random oracles. We present a scheme that is resilient to any leakage of length (1−o(1))L bits, where L is the length of the signing key. Our approach relies on generic cryptographic primitives, and at the same time admits rather efficient instantiations based on specific number-theoretic assumptions. In addition, we show that our approach extends to the continual-leakage model, recently introduced by Dodis, Haralambiev, Lopez-Alt and Wichs (FOCS’10), and by Brakerski, Tauman Kalai, Katz and Vaikuntanathan (FOCS’10). In this model the signing key is allowed to be refreshed, while its corresponding verification key remains fixed, and the amount of leakage is assumed to be bounded only in between any two successive key refreshes.

Communicated by Jonathan Katz
Solicited from Eurocrypt 2011. A preliminary version of this work appeared in Advances in Cryptology—EUROCRYPT’11, pp. 89–108, 2011.
Research of E. Boyle was supported by the US National Defense Science and Engineering Graduate Fellowship. This work was partially completed while visiting the Weizmann Institute of Science.
This work was partially completed while G. Segev was a Ph.D. student at the Weizmann Institute of Science, and supported by the Adams Fellowship Program of the Israel Academy of Sciences and Humanities.
This work of D. Wichs was partially completed while visiting the Weizmann Institute of Science.