Faster Zero-Knowledge Protocols and Applications

Abstract

Zero-knowledge (ZK) protocols are one of the cornerstones of modern cryptography. In a nutshell, a ZK protocol allows a prover P (with a secret input x) to persuade a verifier V that \(f(x)=1\) for some public function f, without disclosing to V any other information about x. In this talk I will present two recent ZK protocols, known as ZKGC [JKO13, FNO15] and ZKBoo [GMO16]. These are the first ZK protocols that allow to prove interesting, non-algebraic statements (such as “I know x such that SHA-256(x) = y” for a public y), in the order of tens of milliseconds on a standard computer. As ZK protocols are ubiquitous in cryptography, this line of research has already enabled many interesting applications. In particular, I will show how ZKBoo allows to construct post-quantum signature schemes using symmetric-key primitives [CDG+17] only.