Zero-Knowledge Arguments and Public-Key Cryptography

In this work we consider the Di e-Hellman Public-key model in which an additional short random string is shared by all users. This, which we call Public-Key Public-Randomness (PKPR) model, is very powerful as we show that it supports simple non-interactive implementations of important cryptographic primitives. We give a non-interactive implementation of Oblivious Transfer in the PKPR model. Our implementation is secure against receivers with unlimited computational power. Building on this result, we show that all languages in NP have Perfect Zero-Knowledge Arguments in the PKPR model.