Vantage: Availability-Graded Broadcast for Signature-Free BFT
2026-08-17 • Distributed, Parallel, and Cluster Computing
Distributed, Parallel, and Cluster ComputingCryptography and Security
AI summaryⓘ
The authors introduce Vantage, a new system that helps a group of computers agree on the order of data blocks even if some fail or act maliciously, without using digital signatures. Instead, it relies on secure channels and hashing, with a method called Availability-Graded Broadcast to handle data efficiently and safely. They show that Vantage can quickly confirm block proposals and works well even with network delays, proving its safety and eventual progress. Testing on a wide-area network with many parties demonstrated Vantage achieves low delays and high transaction rates compared to other systems.
Byzantine fault toleranceauthenticated channelshashingdigital signaturesquorumavailability voteblockchainconsensus protocollatencyGlobal Stabilization Time
Authors
Nikita Polyanskii
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.