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TetraBFT: Reducing Latency of Unauthenticated, Responsive BFT Consensus

Qianyu Yu, Giuliano Losa, Xuechao Wang

TL;DR

TetraBFT tackles unauthenticated, partially synchronous BFT by designing a view-based protocol with seven phases, constant local storage, and quadratic per-view communication, achieving a good-case latency of 5 message delays under $n \ge 3f+1$. It provides detailed liveness and safety proofs, formal verification via a TLA+ specification and Apalache, and extends to a pipelined multi-shot SMR enabling blockchain-like finality with potentially fivefold throughput gains. The work positions itself as strictly faster in the good case than prior unauthenticated protocols like IT-HS while maintaining minimal cryptographic assumptions, and it demonstrates the feasibility of pipelining unauthenticated BFT protocols. The results have practical implications for high-efficiency blockchain systems and trustless cross-chain mechanisms, with future work focusing on real-world implementation and evaluation in heterogeneous trust environments.

Abstract

This paper presents TetraBFT, a novel unauthenticated Byzantine fault tolerant protocol for solving consensus in partial synchrony, eliminating the need for public key cryptography and ensuring resilience against computationally unbounded adversaries. TetraBFT has several compelling features: it necessitates only constant local storage, has optimal communication complexity, satisfies optimistic responsiveness -- allowing the protocol to operate at actual network speeds under ideal conditions -- and can achieve consensus in just 5 message delays, which outperforms all known unauthenticated protocols achieving the other properties listed. We validate the correctness of TetraBFT through rigorous security analysis and formal verification. Furthermore, we extend TetraBFT into a multi-shot, chained consensus protocol, making a pioneering effort in applying pipelining techniques to unauthenticated protocols. This positions TetraBFT as a practical and deployable solution for blockchain systems aiming for high efficiency.

TetraBFT: Reducing Latency of Unauthenticated, Responsive BFT Consensus

TL;DR

TetraBFT tackles unauthenticated, partially synchronous BFT by designing a view-based protocol with seven phases, constant local storage, and quadratic per-view communication, achieving a good-case latency of 5 message delays under . It provides detailed liveness and safety proofs, formal verification via a TLA+ specification and Apalache, and extends to a pipelined multi-shot SMR enabling blockchain-like finality with potentially fivefold throughput gains. The work positions itself as strictly faster in the good case than prior unauthenticated protocols like IT-HS while maintaining minimal cryptographic assumptions, and it demonstrates the feasibility of pipelining unauthenticated BFT protocols. The results have practical implications for high-efficiency blockchain systems and trustless cross-chain mechanisms, with future work focusing on real-world implementation and evaluation in heterogeneous trust environments.

Abstract

This paper presents TetraBFT, a novel unauthenticated Byzantine fault tolerant protocol for solving consensus in partial synchrony, eliminating the need for public key cryptography and ensuring resilience against computationally unbounded adversaries. TetraBFT has several compelling features: it necessitates only constant local storage, has optimal communication complexity, satisfies optimistic responsiveness -- allowing the protocol to operate at actual network speeds under ideal conditions -- and can achieve consensus in just 5 message delays, which outperforms all known unauthenticated protocols achieving the other properties listed. We validate the correctness of TetraBFT through rigorous security analysis and formal verification. Furthermore, we extend TetraBFT into a multi-shot, chained consensus protocol, making a pioneering effort in applying pipelining techniques to unauthenticated protocols. This positions TetraBFT as a practical and deployable solution for blockchain systems aiming for high efficiency.
Paper Structure (20 sections, 10 theorems, 3 figures, 1 table, 5 algorithms)

This paper contains 20 sections, 10 theorems, 3 figures, 1 table, 5 algorithms.

Table of Contents

  1. Introduction
  2. Protocol Overview
  3. Related Work
  4. Model and Preliminary Definitions
  5. Basic TetraBFT
  6. Messages
  7. Evolution of a View
  8. Helper Algorithms
  9. Security Analysis
  10. Liveness Argument
  11. Safety Argument
  12. Main Theorem
  13. formal verification
  14. Multi-Shot TetraBFT
  15. Multi-Shot TetraBFT in the Good Case
  16. ...and 5 more sections

Key Result

Lemma 1

If a well-behaved node sends a vote-1 message for value $val$ in view $v$, it will claim $val$ is safe at any view $\le v$ in its proof message in views greater than $v$. Similarly, if a well-behaved node sends a vote-2 message for value $val$ in view $v$, it will claim $val$ is safe at any view $\l

Figures (3)

  • Figure 1: Liveness lemmas logical framework.
  • Figure 2: Example of Multi-shot TetraBFT in the good case.
  • Figure 3: Example of Multi-shot TetraBFT with failed blocks.

Theorems & Definitions (12)

  • Definition 1: Consensus
  • Definition 2: Multi-shot Consensus
  • Lemma 1
  • Lemma 2
  • Lemma 3
  • Lemma 4
  • Lemma 5
  • Lemma 6
  • Lemma 7
  • Lemma 8
  • ...and 2 more