Strong Leakage and Tamper-Resilient PKE from Refined Hash Proof System

Abstract

We revisit the problem of constructing public key encryption (PKE) secure against both key-leakage and tampering attacks. First, we present an enhanced security against both kinds of attacks, namely strong leakage and tamper-resilient chosen-ciphertext (sLTR-CCA) security, which imposes only minimal restrictions on the adversary’s queries and thus captures the capability of the adversary in a more reasonable way. Then, we propose a generic paradigm achieving this security on the basis of a refined hash proof system (HPS) called public-key-malleable HPS. The paradigm can not only tolerate a large amount of bounded key-leakage, but also resist an arbitrary polynomial of restricted tampering attacks, even depending on the challenge phase. Moreover, the paradigm with slight adaptations can also be proven sLTR-CCA secure with respect to subexponentially hard auxiliary-input leakage. In addition, we instantiate our paradigm under certain standard number-theoretic assumptions, and thus, to our best knowledge, obtain the first efficient PKE schemes possessing the strong bounded/auxiliary-input leakage and tamper-resilient chosen-ciphertext security in the standard model.