On the Security of Leakage Resilient Public Key Cryptography

Side channel attacks, where an attacker learns some physical information about the state of a device, are one of the ways in which cryptographic schemes are broken in practice. "Provably secure" schemes are subject to these attacks since the traditional models of security do not account for them. The theoretical community has recently proposed leakage resilient cryptography in an effort to account for side channel attacks in the security model. This thesis provides an in-depth look into what security guarantees public key leakage resilient schemes provide in practice

Protecting Circuits from Computationally-Bounded Leakage

Abstract. Physical computational devices leak side-channel information that may, and often does, reveal secret internal states. We present a general transformation that compiles any circuit into a device that maintains secrecy even in the presence of well-defined classes of side-channel leakage. Our construction requires only a minimal leak-proof component: one that draws random elements from a simple distribution. We thus reduce the problem of shielding arbitrary complex circuits to the problem of shielding a single simple component. Our approach is based on modeling the adversary as a powerful observer that inspects the device via a “limited ” measurement apparatus. We capture the notion of “limited ” measurements using computational complexity classes, and our proofs of security rely on the hardness of certain functions for these classes. Thus, for example, AC 0 lower bounds yield a construction that is resilient to any leakage that can be computed by constant-depth circuits. More generally, we give a generic composition theorem that shows how to build a provably secure devices of arbitrary complexity out of components that satisfy a simulatability condition. Several applications are shown. In contrast to previous works, we allow the side-channel leakage to depend on the whole state and on all the wires in the device, and to grow unbounded over time.