CelesBFT Overview
CelesBFT is the consensus protocol used by Celestium to achieve fast, secure, and deterministic finality in a decentralized environment. It is designed to handle high-throughput blockchain operations while ensuring Byzantine Fault Tolerance (BFT) and Proof-of-Authority combined with AI (PoAi) for Sybil resistance.
Key Characteristics
Sybil Resistance
Proof-of-Authority + AI (PoAi)
Block Time
1 second
Finality
Single-slot finality (block finalized after 1 second)
Delegation
Supported
Pipelined Rounds
Optimized two-phase consensus rounds with pipelining
Optimistic Responsiveness
Fast finality under normal conditions
BLS Multi-Signatures
Efficient certificate aggregation with BLS12-381 curve
How CelesBFT Works
CelesBFT is a pipelined, two-phase consensus protocol adapted from HotStuff with enhancements from DiemBFT and Jolteon. It optimizes transaction finality and leader rotation while minimizing communication overhead.
Consensus Participants
Leader: Proposes a block containing transactions.
Validators: Validate the proposed block and vote on its validity.
Round Structure
Each consensus round consists of the following steps:
Proposal: The leader broadcasts a block proposal with a quorum certificate (QC) or timeout certificate (TC) for the previous round.
Voting: Validators verify the block and sign a YES vote if valid.
Quorum Certificate (QC): If 2f + 1 votes are received (f is the number of tolerated Byzantine nodes), the next leader aggregates the signatures into a QC.
Timeout Certificate (TC): If a block is not proposed on time, validators submit timeout messages. Upon reaching 2f + 1, a TC is formed.
Finality: A block is considered finalized when a QC for the subsequent block is formed.
2-Chain Commit Rule
A block is finalized when two consecutive certified blocks are observed:
Block k is finalized when a QC is formed for Block k+1 and a valid proposal for Block k+2 is seen.
BLS Multi-Signatures
CelesBFT uses BLS signatures for aggregating validator votes:
BLS12-381 Curve: Allows signature aggregation into a single signature.
ECDSA: Used for other message types for performance efficiency.
The blend of BLS and ECDSA ensures both performance and compactness in consensus messages.
Fault Tolerance
CelesBFT can tolerate up to f Byzantine nodes in a network of 3f + 1 validators. This guarantees consensus safety and liveness as long as at least 2/3 of the validators are honest.
Finality and Reorg Resistance
Single-Slot Finality: Once a block is finalized, it is irreversible unless a supermajority behaves maliciously.
Finality Time: 1 second per block, offering faster transaction confirmation compared to probabilistic finality systems like Ethereum Proof-of-Stake.
Advantages of CelesBFT
Fast Finality: Transactions are confirmed in 1 second.
Efficiency: Reduced communication complexity in the happy path.
Scalability: Supports high transaction throughput due to pipelined processing.
Security: Robust Byzantine Fault Tolerance with cryptographic signature aggregation.
CelesBFT’s combination of performance and security makes it a cornerstone of Celestium’s high-throughput Layer 1 blockchain architecture.
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