Synchronous Consensus with Optimal Asynchronous Fallback Guarantees

Blum, Erica; Katz, Jonathan; Loss, Julian

doi:10.1007/978-3-030-36030-6_6

Cited by 32 publications

(40 citation statements)

References 27 publications

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“…Then, in Section F, we show a version running in expected constantrounds when the network is synchronous. 4 While the optimal achievable trade-off (see [9]) of a BA protocol with full asynchronous fallback security is t a + 2t s < n and t a ≤ t s (which together imply t s < n/2), we show that there is room for improvement when only requiring asynchronous weak-validity. In this case, we prove the optimal threshold trade-off to be 2t a + t s < n and t s < n/2.…”

Section: Round-efficient Byzantine Agreement With Asynchronous Weak Validitymentioning

confidence: 80%

“…Protocols achieving security guarantees in both synchronous and asynchronous networks have only begun to be studied in relatively recent works. Closest to ours are works by Blum et al [9,11], which consider the problem of BA and MPC achieving security guarantees in both communication models. Our work improves upon the round efficiency of these protocols.…”

Section: Related Workmentioning

confidence: 93%

“…A recent line of work [9,11] provides BA and MPC protocols that are secure up to t s < n/2 corruptions when the network is synchronous, and t a ≤ t s corruptions when the network is asynchronous, for the optimal trade-off t a + 2t s < n.…”

Section: Contributionsmentioning

confidence: 99%

“…Current BA and MPC protocols in this realm [9,11] require a linear number of rounds in the number of parties. Moreover, known MPC protocols [11] also have linear round complexity in the depth of the circuit to evaluate.…”

Section: Contributionsmentioning

confidence: 99%

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Round-Efficient Byzantine Agreement and Multi-party Computation with Asynchronous Fallback

Deligios

Hirt

Liu-Zhang

2021

Lecture Notes in Computer Science

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Protocols for Byzantine agreement (BA) and secure multi-party computation (MPC) can be classified according to the underlying communication model. The two most commonly considered models are the synchronous one and the asynchronous one. Synchronous protocols typically lose their security guarantees as soon as the network violates the synchrony assumptions. Asynchronous protocols remain secure regardless of the network conditions, but achieve weaker security guarantees even when the network is synchronous. Recent works by Blum, Katz and Loss [TCC'19], and Blum, Liu-Zhang and Loss [CRYPTO'20] introduced BA and MPC protocols achieving security guarantees in both settings: security up to ts corruptions in a synchronous network, and up to ta corruptions in an asynchronous network, under the provably optimal threshold trade-offs ta ≤ ts and ta + 2ts < n. However, current solutions incur a high synchronous round complexity when compared to state-of-the-art purely synchronous protocols. When the network is synchronous, the round complexity of BA protocols is linear in the number of parties, and the round complexity of MPC protocols also depends linearly on the depth of the circuit to evaluate. In this work, we provide round-efficient constructions for both primitives with optimal resilience: fixed-round and expected constant-round BA protocols, and an MPC protocol whose round complexity is independent of the circuit depth.

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Section: Round-efficient Byzantine Agreement With Asynchronous Weak Validitymentioning

confidence: 80%

Section: Related Workmentioning

confidence: 93%

Section: Contributionsmentioning

confidence: 99%

Section: Contributionsmentioning

confidence: 99%

See 2 more Smart Citations

Round-Efficient Byzantine Agreement and Multi-party Computation with Asynchronous Fallback

Deligios

Hirt

Liu-Zhang

2021

Lecture Notes in Computer Science

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“…Flexibility in BFT protocols. A recent line of work investigates synchronous BFT protocol with an asynchronous fallback, focusing on achieving optimal resilience tradeoffs between synchrony and asynchrony [5,6] or optimal communication complexity [27]. Another related line of work on optimistic BFT protocols focuses on including a fast path in BFT protocols to improve the performance such as communication complexity and latency under the optimistic scenarios, for asynchronous protocols [19][20][21]27], partially synchronous protocols [1,15,18] and synchronous protocols [10,[24][25][26].…”

Section: Related Workmentioning

confidence: 99%

Brief Announcement

Gelashvili

Kokoris-Kogias

Spiegelman

et al. 2021

Proceedings of the 2021 ACM Symposium on Principles of Distributed Computing

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The popularity of permissioned blockchain systems demands BFT SMR protocols that are efficient under good network conditions (synchrony) and robust under bad network conditions (asynchrony). The state-of-the-art partially synchronous BFT SMR protocols provide optimal linear communication cost per decision under synchrony and good leaders, but lose liveness under asynchrony. On the other hand, the state-of-the-art asynchronous BFT SMR protocols are live even under asynchrony, but always pay quadratic cost even under synchrony. In this paper, we propose a BFT SMR protocol that achieves the best of both worlds -optimal linear cost per decision under good networks and leaders, optimal quadratic cost per decision under bad networks, and remains always live. CCS CONCEPTS• Theory of computation → Distributed algorithms; • Security and privacy → Distributed systems security.

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