# CSAIL Event Calendar: Previous Series

 On the Difficulty of Perfect NIZK with Adaptive SecuritySpeaker: Masayuki Abe , NTTDate: April 21 2006 Time: 10:30AM to 12:00PM Location: 32-G449 (Patil/Kiva)Contact: Be Blackburn, 3-6098, imbe@mit.eduThe notion of non-interactive zero-knowledge (NIZK), introduced by Blum, Feldman and Micali, is of fundamental importance in cryptography. Despite the vast attention the concept of NIZK has attracted since its introduction in the late 80's, one question has remained open until recently: Is it possible to construct NIZK schemes for any $\np$-language with {\em statistical} (or even {\em perfect}) ZK? Groth, Ostrovsky and Sahai recently proposed two elegant constructions for perfect NIZK arguments for any $\np$-language $L$. However, their schemes achieve non-adaptive security, meaning security against a dishonest prover that chooses the target instance \mbox{$x^* \not\in L$} (for which he wants to fake a proof) {\em independent} of the common reference string (CRS), or need strong non-standard assumption to achieve adaptive security. But is such a strong assumption inevitable in general? In this talk, we show that using standard techniques'' it is not possible to construct a statistical NIZK argument for an $\np$-complete language with adaptive security unless \mbox{$\np \in \ppoly$}. This is a joint work with Serge Fehr (CWI).See other events that are part of Cryptography and Information Security Seminar Seminars 2005/2006See other events happening in April 2006