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.

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Key Characteristics

Feature	Description
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

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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:

1. Proposal: The leader broadcasts a block proposal with a quorum certificate (QC) or timeout certificate (TC) for the previous round.

2. Voting: Validators verify the block and sign a YES vote if valid.

3. 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.

4. Timeout Certificate (TC): If a block is not proposed on time, validators submit timeout messages. Upon reaching 2f + 1, a TC is formed.

5. Finality: A block is considered finalized when a QC for the subsequent block is formed.

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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.

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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.

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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.

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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.

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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.