Concurrent and Resettable Zero-Knowledge in Poly-logarithmic Rounds [ Extended Abstract ]

A proof is on urrent zero-knowledge if it remains zeroknowledge when many opies of the proof are run in an asyn hronous environment, su h as the Internet. Ri hardson and Kilian have shown that there exists a on urrent zeroknowledge proof for any language in NP, but with round omplexity polynomial in the maximum number of on urrent proofs. In this paper, we present a on urrent zeroknowledge proof for all languages in NP with a poly-logarithmi round omplexity: spe i ally, !(log2 k) rounds given at most k on urrent proofs. Finally, we show that a simple modi ation of our proof is a resettable zero-knowledge proof for NP, with !(log2 k) rounds; previously known proto ols required a polynomial number of rounds.