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The Stellar Consensus Protocol: A Federated Byzantine Agreement Model

This whitepaper introduces the Stellar Consensus Protocol (SCP), a novel consensus mechanism based on Federated Byzantine Agreement (FBA). SCP offers an alterna

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Abstract

This whitepaper introduces the Stellar Consensus Protocol (SCP), a novel consensus mechanism based on Federated Byzantine Agreement (FBA). SCP offers an alternative to traditional Byzantine Fault Tolerance (BFT) by replacing the requirement for a global agreement on network membership with a system where each node independently chooses its “quorum slices” – sets of other nodes it trusts for agreement. Consensus is achieved when all members of all relevant quorum slices agree on a transaction. This methodology enables open membership and decentralized control, allowing for flexible trust relationships and reducing the barriers to entry for participants. SCP is designed to provide safety (guaranteeing that transactions are irreversible once confirmed), liveness (ensuring the network continues to make progress), and low latency, without requiring a closed or centrally managed network. The paper provides a formal definition of FBA and demonstrates how SCP achieves these properties, making it a significant contribution to decentralized consensus design and the foundation of the Stellar network. Authors: David Mazières Publication: Project Whitepaper Publication date: 2015-01-01

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Key findings

  • The Stellar Consensus Protocol (SCP) is based on Federated Byzantine Agreement (FBA), a new class of consensus.
  • Nodes define their own “quorum slices” (trusted sets of other nodes) instead of relying on global membership agreement.
  • SCP achieves safety, liveness, and low latency without requiring a fixed, known set of participants.
  • It supports open membership and flexible trust, fostering decentralized control.
  • The paper formally defines FBA and outlines SCP’s properties and mechanisms.

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Citation

David Mazières (2015). The Stellar Consensus Protocol: A Federated Byzantine Agreement Model. Project Whitepaper. https://www.stellar.org/papers/stellar-consensus-protocol.pdf
Canonical knowledge ID: research:the-stellar-consensus-protocol-a-federated-byzantine-agreement-model