Journal of Cryptology

, Volume 18, Issue 3, pp 219–246 | Cite as

Random Oracles in Constantinople: Practical Asynchronous Byzantine Agreement Using Cryptography

  • Christian Cachin
  • Klaus Kursawe
  • Victor Shoup


Byzantine agreement requires a set of parties in a distributed system to agree on a value even if some parties are maliciously misbehaving. A new protocol for Byzantine agreement in a completely asynchronous network is presented that makes use of new cryptographic protocols, specifically protocols for threshold signatures and coin-tossing. 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 optimal because it tolerates the maximum number of corrupted parties, runs in constant expected rounds, has message and communication complexity close to the optimum, and uses a trusted dealer only once 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.

Asynchronous consensus Byzantine faults Threshold signatures Cryptographic common coin Dual-threshold schemes 


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Copyright information

© Springer 2005

Authors and Affiliations

  1. 1.IBM Research GmbH, Zurich Research Laboratory, CH-8803 RuschlikonSwitzerland
  2. 2.ESAT-COSIC, Katholieke Universiteit Leuven, B-3001 Leuven-HeverleeBelgium
  3. 3.Computer Science Department, Courant Institute of Mathematical Sciences, New York University, New York, NY 10012USA

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