Cryptology ePrint Archive: Report 1999/014

Concurrent Zero-Knowledge is Easy in Practice

Ivan Damgard

Abstract: We show that if any one-way function exists, then 3-round concurrent zero-knowledge arguments for all NP problems can be built in a model where a short auxiliary string with a prescribed distribution is available to the players. We also show that all known efficient identification schemes using specialized assumptions can be modified to work in this model with no essential loss of efficiency. We argue that the assumptions of the model will be satisfied in most practical scenarios where public key cryptography is used, in particular our construction works given any secure public key infrastructure. Finally, we point out that in a model with preprocessing (and no auxiliary string) proposed earlier, concurrent zero-knowledge for NP can be based on any one-way function.

Category / Keywords: Concurrent Zero-Knowledge, Protocols, Proofs of knowledge.

Publication Info: Appeared in the THEORY OF CRYPTOGRAPHY LIBRARY and has been included in the ePrint Archive.

Date: received June 16th, 1999. Revised July 28th, 1999.

Contact author: ivan at daimi aau dk

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