Sawtooth PBFT is a consensus engine for Hyperledger Sawtooth that provides practical Byzantine fault tolerance.
PBFT is a voting-based consensus algorithm that is:
- Byzantine fault tolerant: Network liveness and safety are guaranteed even when some nodes are faulty or malicious, as long as a minimum percentage of nodes are connected, working properly, and behaving honestly.
- Non-forking: Blocks committed by nodes are final, unlike lottery-style consensus algorithms such as Proof of Work (PoW) or Proof of Elapsed Time (PoET).
- Leader-based: A primary node is responsible for producing candidate blocks; secondary nodes vote on the blocks produced by the primary. The leader changes in a round-robin (circular) order.
- Communication-intensive: Nodes send many messages to reach consensus, commit blocks, and maintain a healthy leader node.
A Sawtooth PBFT network does not support open enrollment, but nodes can be added and removed by an administrator. Full peering is required (all nodes must be connected to all other nodes). In order to provide Byzantine fault tolerance, a PBFT network must have a least four nodes.
Sawtooth PBFT is based on the methodology described in Practical Byzantine Fault Tolerance by Miguel Castro and Barbara Liskov. This implementation has been adapted for use in a blockchain context; it includes extensions such as regular view changes (leader changes) and a consensus seal to verify block finality.
Sawtooth PBFT uses the terms “primary” and “secondary” to refer to the role of nodes in the network, which differs slightly from the terminology used in the PBFT paper.
- “Primary” is synonymous with “leader”
- “Secondary” is synonymous with “follower” and “backup”
- “Node” is synonymous with “server” and “replica”
For implementation details, see the rustdoc for Sawtooth PBFT.