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### Paper:

TR07-065 | 13th July 2007 00:00

#### Which Languages Have 4-Round Zero-Knowledge Proofs?

TR07-065
Authors: Jonathan Katz
Publication: 23rd July 2007 09:32
We show that if a language $L$ has a 4-round, black-box, computational zero-knowledge proof system with negligible soundness error, then $\bar L \in MA$. Assuming the polynomial hierarchy does not collapse, this means, in particular, that $NP$-complete languages do not have 4-round zero-knowledge proofs (at least with respect to black-box simulation).