International Association for Cryptologic Research

International Association
for Cryptologic Research


Paper: On Expected Constant-Round Protocols for Byzantine Agreement

Jonathan Katz
Chiu-Yuen Koo
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Abstract: In a seminal paper, Feldman and Micali (STOC '88) show an $n$-party Byzantine agreement protocol tolerating $t < n/3$ malicious parties that runs in expected constant rounds. Here, we show an expected constant-round protocol for authenticated Byzantine agreement assuming honest majority (i.e., $t < n/2$), and relying only on the existence of a secure signature scheme and a public-key infrastructure (PKI). Combined with existing results, this gives the first expected constant-round protocol for secure computation with honest majority in a point-to-point network assuming only one-way functions and a PKI. Our key technical tool --- a new primitive we introduce called moderated VSS --- also yields a simpler proof of the Feldman-Micali result. We also show a simple technique for sequential composition of protocols without simultaneous termination (something that is inherent for Byzantine agreement protocols using $o(n)$ rounds) for the case of $t<n/2$.
  title={On Expected Constant-Round Protocols for Byzantine Agreement},
  booktitle={IACR Eprint archive},
  keywords={cryptographic protocols / distributed computing, multiparty computation},
  note={An extended abstract will appear at Crypto 2006 13291 received 20 Feb 2006, last revised 23 May 2006},
  author={Jonathan Katz and Chiu-Yuen Koo},