Concurrent non-malleable zero-knowledge (NMZK) considers the concurrent execution of zero-knowledge protocols in a setting where the attacker can simultaneously corrupt multiple provers and verifiers. Barak, Prabhakaran and Sahai (FOCS’06) recently provided the first construction of a concurrent NMZK protocol without any set-up assumptions. Their protocol, however, is only computationally sound...

We consider a public and keyless code (Enc,Dec) which is used to encode a message m and derive a codeword c = Enc(m). The codeword can be adversarially tampered via a function f ∈ F from some “tampering function family” F , resulting in a tampered value c′ = f(c). We study the different types of security guarantees that can be achieved in this scenario for different families F of tampering atta...

Andris Ambainis,1, 2 Jan Bouda,3 and Andreas Winter4, 5 Department of Computer Science, University of Latvia, Raina bulv. 19, Riga, LV-1586, Latvia Department of Combinatorics and Optimization & Institute for Quantum Computing, University of Waterloo Faculty of Informatics, Masaryk University, Botanická 68a, 602 00 Brno, Czech Republic Department of Mathematics, University of Bristol, Bristol B...

We introduce the notion of non-malleable noninteractive zero-knowledge (NIZK) proof systems. We show how to transform any ordinary NIZK proof system into one that has strong non-malleability properties. We then show that the elegant encryption scheme of Naor and Yung [NY] can be made secure against the strongest form of chosen-ciphertext attack by using a non-malleable NIZK proof instead of a s...

It is known that composable secure commitments, that is, concurrent non-malleable commitments exist in the plain model, based only on standard assumptions such as the existence of claw-free permutations or even one-way functions. Since being based on the plain model, the deniability of them is trivially satisfied, and especially the latter scheme satisfies also adaptivity, hence it is adaptived...

One of the central questions in Cryptography is the design of round-efficient protocols that are secure under concurrent man-in-the-middle attacks. In this paper we present the first constant-round concurrent non-malleable zero-knowledge argument system for NP in the Bare Public-Key model [Canetti et al. STOC 2000], resolving one of the major open problems in this area. To achieve our result, w...

Under the assumption of the existence of one-way functions, we prove that it is possible to construct the non-interactive equivocable non-malleable commitment scheme. Especially importantly, we succeed in implementing concurrent zero-knowledge using our commitment scheme, analysising properties of this concurrent zero-knowledge proof system, comparing it with the existed concurrent zero-knowled...