Strict polynomial-time in simulation and extraction

The notion of efficient computation is usually identified in cryptography and complexity with (strict) probabilistic polynomial time. However, until recently, in order to obtain constant-round zero-knowledge proofs and proofs of knowledge, one had to allow simulators and knowledgeextractors to run in time that is only polynomial on the average (i.e., expected polynomial time). Recently Barak gave the first constant-round zero-knowledge argument with a strict (in contrast to expected) polynomial-time simulator. The simulator in his protocol is a non-blackbox simulator (i.e., it makes inherent use of the description of the code of the verifier). In this paper, we further address the question of strict polynomial-time in constant-round zero-knowledge proofs and arguments of knowledge. First, we show that there exists a constantround zero-knowledge argument of knowledge with a strict polynomial-time knowledge extractor. As in the simulator of Barak's zero-knowledge protocol, the extr...

• Type: Conference
• Year: 2002
• Where: STOC
• Authors: Boaz Barak, Yehuda Lindell
• Keywords: Algorithms, Constant-round Zero-knowledge Proof, Constant-round Zero-knowledge Proofs, STOC 2002, Strict Polynomial-time