Hashing Functions can Simplify Zero-Knowledge Protocol Design (too)

In <em>Crypto93</em>, Damgård showed that any constant-round protocol in which the verifier sends only independent, random bits and which is zero-knowledge against the <em>honest</em> verifier can be transformed into a protocol (for the same problem) that is zero-knowledge <em>in general</em>. His transformation was based on the interactive hashing technique of Naor, Ostrovsky, Venkatesan and Yung, and thus the resulting protocol had very large round-complexity.