Michael Ben-Or Oded Goldreich Shafi Goldwasser Johan Håstad Joe Kilian Silvio Micali Phillip Rogaway Everything Provable is Provable in Zero-Knowledge. 37-56 http://dx.doi.org/10.1007/0-387-34799-2_4 1988 conf/crypto/1988 CRYPTO db/conf/crypto/crypto88.html#Ben-OrGGHKMR88