Abstract

We initiate a study of zero knowledge proof systems in the presence of side-channel attacks. Specifically, we consider a setting where a cheating verifier is allowed to obtain arbitrary bounded leakage on the entire state (including the witness and the random coins) of the prover during the entire protocol execution. We formalize a meaningful definition of leakage-resilient zero knowledge (LR-ZK) proof system, that intuitively guarantees that “the protocol does not yield anything beyond the validity of the statement, and whatever leakage the attacker could have obtained without the protocol ever taking place.” We give a construction of LR-ZK interactive proof system based on general assumptions. To the best of our knowledge, this is the first instance of a cryptographic protocol where the adversary is allowed to perform leakage attacks during the protocol execution (in contrast, prior work only focused on leakage-resilient primitives such as encryption, or leakage-resilient devices, or leakage prior to the protocol execution). Next, we give an LR-NIZK argument system based on standard assumptions. We will also discuss several applications of our new notion. Joint work with Sanjam Garg and Abhishek Jain.