Cryptology ePrint Archive: Report 2018/377

ALGORAND AGREEMENT: Super Fast and Partition Resilient Byzantine Agreement

Jing Chen and Sergey Gorbunov and Silvio Micali and Georgios Vlachos

Abstract: We present a simple Byzantine agreement protocol with leader election, that works under > 2/3 honest majority and does not rely on the participants having synchronized clocks. When honest messages are delivered within a bounded worst-case delay, agreement is reached in expected constant number of steps when the elected leader is malicious, and is reached after two steps when the elected leader is honest. Our protocol is resilient to arbitrary network partitions with unknown length, and recovers fast after the partition is resolved and bounded message delay is restored. We will briefly discuss how the protocol applies to blockchains in a permissionless system. In particular, when an honest leader proposes a block of transactions, the first voting step happens in parallel with the block propagation. Effectively, after the block propagates, a certificate is generated in just one step of voting.

Category / Keywords: blockchain, proof-of-stake, consensus, Byzantine agreement

Date: received 25 Apr 2018, last revised 1 May 2018

Contact author: georgios at algorand com

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Version: 20180501:150853 (All versions of this report)

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