@article {15176,
	title = {Which languages have 4-round zero-knowledge proofs?},
	journal = {Theory of Cryptography},
	year = {2008},
	month = {2008///},
	pages = {73 - 88},
	abstract = {We show that if a language L has a 4-round, black-box, computational zero-knowledge proof system with negligible soundness error, then . 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).},
	doi = {10.1007/978-3-540-78524-8_5},
	author = {Katz, Jonathan}
}
