## Cryptology ePrint Archive: Report 2000/034

Random Oracles in Constantinople: Practical Asynchronous Byzantine Agreement using Cryptography

Christian Cachin and Klaus Kursawe and Victor Shoup

Abstract: Byzantine agreement requires a set of parties in a distributed system to agree on a value even if some parties are corrupted. A new protocol for Byzantine agreement in a completely asynchronous network is presented that makes use of cryptography, specifically of threshold signatures and coin-tossing protocols. These cryptographic protocols have practical and provably secure implementations in the random oracle'' model. In particular, a coin-tossing protocol based on the Diffie-Hellman problem is presented and analyzed. The resulting asynchronous Byzantine agreement protocol is both practical and theoretically nearly optimal because it tolerates the maximum number of corrupted parties, runs in constant expected time, has message and communication complexity close to the optimum, and uses a trusted dealer only in a setup phase, after which it can process a virtually unlimited number of transactions. The protocol is formulated as a transaction processing service in a cryptographic security model, which differs from the standard information-theoretic formalization and may be of independent interest.

Category / Keywords: cryptographic protocols / consensus, Byzantine faults, threshold signatures, common coin, dual-threshold schemes

Publication Info: Extended abstract appears in Proc. PODC 2000

Date: received 7 Jul 2000, revised 14 Aug 2000

Contact author: cachin at acm org

Available format(s): Postscript (PS) | Compressed Postscript (PS.GZ) | PDF | BibTeX Citation

Short URL: ia.cr/2000/034

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