Proving security against chosen ciphertext attacks

Abstract

The relevance of zero knowledge to cryptography has become apparent in the recent years. In this paper we advance this theory by showing that interaction in any zero-knowledge proof can be replaced by sharing a common, short, random string. This advance finds immediate application in the construction of the first public-key cryptosystem secure against chosen ciphertext attack. Our solution, though not yet practical, is of theoretical significance, since the existence of cryptosystems secure against chosen ciphertext attack has been a famous long-standing open problem in the field.