Federated Byzantine Agreement

Written by Eric Choy

Introduction

The Federated Byzantine Agreement, also the main consensus protocol utilized in the Stellar Consensus Protocol, was created by David Mazières, a professor at Stanford. This consensus protocol is an improvement on its predecessor, the original Byzantine Agreement, which is a way to become Byzantine Fault Tolerant (BFT). The BFT is essentially a way of overcoming the Byzantine General’s Problem of being able to reach consensus in a distributed system. The original Byzantine Agreement allowed consensus to be reached, despite the possibility of having failed nodes, through a list of approved validators. But this essentially pits the whole system as being centralized.

The Federated Byzantine Agreement is a decentralized version of the original Byzantine Agreement. This works through consensus amongst quorums, which are clustered groups of nodes that trust each other. Quorums can overlap as well, which allows different quorums to reach consensus amongst each other. And until all quorums are in consensus is when a decision can be validated.

Other protocols such as Bitcoin and Ethereum also are considered Byzantine Fault Tolerant through different methods such as Proof-of-Work.

Suggested Reading

Understanding the Stellar Consensus Protocol by Bob Glickstein

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