Vantage: Availability-Graded Broadcast for Signature-Free BFT

2026-08-17

AI Summary

This study addresses the performance bottleneck in signature-free BFT protocols caused by the lack of transferable evidence by proposing Vantage. This protocol introduces Availability-Graded Broadcast (AGB), a novel primitive achieving partially synchronous consensus using only authenticated channels and hash functions. By decoupling block dissemination from ordering and employing a dual-manifest mechanism, Vantage enables single-message-latency participation in proposals. Experimental evaluations in a 100-node WAN demonstrate that Vantage achieves 239,000 TPS with median latency below 500ms while maintaining safety and liveness. These results significantly outperform existing signature-based and signature-free protocols, effectively breaking through the traditional performance ceiling of signature-free consensus systems.

Abstract

Digital signatures make blocks and votes transferable evidence: one party can prove to another what a third party said. Authenticated channels convince only the direct receiver, so existing high-throughput signature-free protocols complete an availability vote or a broadcast instance for each data block before any proposer may order it. We present Vantage, a partially synchronous Byzantine fault-tolerant protocol for $n \ge 3f+1$ parties that uses only authenticated channels and collision-resistant hashing. Parties publish blocks on hash-linked author lanes; each view's proposer pairs a quorum-available core manifest of lane frontiers with an optimistic tip manifest of freshly received blocks. A new primitive, Availability-Graded Broadcast (AGB), makes the core irrevocable on a quorum of first-hand responses while grading, rather than blocking on, the tip. Unresolved tips are sealed later through a signature-free control log, by resolutions each correct party checks against its own recorded responses; a crash-only silent view is skipped by a quorum of skip votes without the log. AGB makes a published block proposal-eligible one message delay after publication, matching signed optimistic-tip designs. When all parties are correct and message delays are $δ$, a data-only proposal seals within $2δ$ of its send on all $n$ first-hand acknowledgments, so a block is sequenced within $4δ$ of publication, and within $3δ$ when publication aligns with the next proposal. We prove safety under asynchrony; liveness holds after the Global Stabilization Time. On an emulated ten-region WAN with 100 parties, Vantage has the lowest median latency among the nearest signature-based and signature-free protocols at every accepted load and sequences 239k 512-byte transactions per second with median latency below 500 ms.

Problem

• Signature-Free BFT
• Authenticated Channels
• Availability-Graded Broadcast
• Byzantine Fault Tolerance
• Low Latency

Innovation

• Availability-Graded Broadcast
• Signature-Free BFT
• Authenticated Channels
• Control Log
• Partial Synchrony