Revisiting asynchronous fault tolerant computation with optimal resilience

Abraham, Ittai; Dolev, Danny; Stern, Gilad

doi:10.1007/s00446-021-00416-4

Cited by 4 publications

(13 citation statements)

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“…Hence, the strong-commitment of AVSS guarantees that if D is corrupt and if some honest party obtains a point on D's polynomial, then all honest parties eventually obtain their respective points on this polynomial. Perfectly-secure AVSS is possible iff t < n/4 [13,4].…”

Section: Technical Overviewmentioning

confidence: 99%

“…It is precisely for this reason that Π SWPS fails to qualify as a VSS. 4), the parties first run Π SWPS assuming a synchronous network, where Π BC is used to make any value public by setting t = t s . If D is honest then in a synchronous network, the first, second, third and fourth phase of Π SWPS would have been over by time ∆, 2∆, 2∆ + T BC and 2∆ + 2T BC respectively and by time 2∆+2T BC , the parties should have accepted (W, E, F).…”

Section: The Best-of-both-worlds Weak Polynomial-sharing (Wps) Protocolmentioning

confidence: 99%

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Perfectly-Secure Synchronous MPC with Asynchronous Fallback Guarantees

Appan¹,

Chandramouli²,

Choudhury³

2022

Preprint

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Secure multi-party computation (MPC) is a fundamental problem in secure distributed computing. The optimal resilience for perfectly-secure MPC in synchronous and asynchronous networks is t < n/3 and t < n/4 respectively, where n is the number of parties and t is the number of corruptions. A natural question is whether there exists a protocol tolerating t s < n/3 corruptions in a synchronous network and t a < n/4 corruptions in an asynchronous network. We design such a protocol, if 3t s + t a < n. For our protocol, we present a perfectly-secure Byzantine agreement (BA) protocol, tolerating t < n/3 corruptions in any network and a perfectly-secure verifiable secret-sharing (VSS) protocol, tolerating t s and t a corruptions in a synchronous and an asynchronous network respectively.

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Section: Technical Overviewmentioning

confidence: 99%

Section: The Best-of-both-worlds Weak Polynomial-sharing (Wps) Protocolmentioning

confidence: 99%

Perfectly-Secure Synchronous MPC with Asynchronous Fallback Guarantees

Appan¹,

Chandramouli²,

Choudhury³

2022

Preprint

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“…In the general-adversary model, MPC with perfect and statistical security is achievable iff Z satisfies the Q (3) (P, Z) and Q (2) (P, Z) conditions respectively. 1 In terms of efficiency, MPC protocols against general adversaries are less efficient than those against threshold adversaries, by several orders of magnitude. Protocols against threshold adversaries typically incur a communication of n O (1) bits per multiplication, compared to |Z| O (1) bits per multiplication required against general adversaries.…”

Section: Introductionmentioning

confidence: 99%

“…1 In terms of efficiency, MPC protocols against general adversaries are less efficient than those against threshold adversaries, by several orders of magnitude. Protocols against threshold adversaries typically incur a communication of n O (1) bits per multiplication, compared to |Z| O (1) bits per multiplication required against general adversaries. 2 Since |Z| could be exponentially large in n, the exact exponent is very important.…”

Section: Introductionmentioning

confidence: 99%

“…To avoid an endless wait, the parties cannot afford to wait to receive messages from all the parties, which results in disregarding messages from a subset of potentially honest parties. Against threshold adversaries, perfectly-secure and statistically-secure asynchronous MPC (AMPC) is achievable, iff t < n/4 [5] and t < n/3 [7,1] respectively. By using the player-partitioning argument [22], these results can be generalized to show that against general adversaries, perfect and statistical security require Z to satisfy the Q (4) (P, Z) and Q (3) (P, Z) conditions respectively.…”

Section: Introductionmentioning

confidence: 99%

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Revisiting the Efficiency of Asynchronous Multi Party Computation Against General Adversaries

Appan¹,

Chandramouli²,

Choudhury³

2022

Preprint

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In this paper, we design secure multi-party computation (MPC) protocols in the asynchronous communication setting with optimal resilience. Our protocols are secure against a computationally-unbounded malicious adversary, characterized by an adversary structure Z, which enumerates all possible subsets of potentially corrupt parties. Our protocols incur a communication of O(|Z| 2 ) and O(|Z|) bits per multiplication for perfect and statistical security respectively. These are the first protocols with this communication complexity, as such protocols were known only in the synchronous communication setting (Hirt and Tschudi, ASIACRYPT 2013).

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Concurrent Asynchronous Byzantine Agreement in Expected-Constant Rounds, Revisited

Cohen,

Forghani,

Garay

et al. 2023

Lecture Notes in Computer Science

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It is well known that without randomization, Byzantine agreement (BA) requires a linear number of rounds in the synchronous setting, while it is flat out impossible in the asynchronous setting. The primitive which allows to bypass the above limitation is known as oblivious common coin (OCC). It allows parties to agree with constant probability on a random coin, where agreement is oblivious, i.e., players are not aware whether or not agreement has been achieved.The starting point of our work is the observation that no known protocol exists for information-theoretic multi-valued OCC-i.e., OCC where the coin might take a value from a domain of cardinality larger than 2-with optimal resiliency in the asynchronous setting (with eventual message delivery). This apparent hole in the literature is particularly problematic, as multi-valued OCC is implicitly or explicitly used in several constructions. (In fact, it is often falsely attributed to the asynchronous BA result by Canetti and Rabin [STOC '93], which, however, only achieves binary OCC and does not translate to a multi-valued OCC protocol.)In this paper, we present the first information-theoretic multi-valued OCC protocol in the asynchronous setting with optimal resiliency, i.e., tolerating t < n/3 corruptions, thereby filling this important gap. Further, our protocol efficiently implements OCC with an exponentialsize domain, a property which is not even achieved by known constructions in the simpler, synchronous setting.We then turn to the problem of round-preserving parallel composition of asynchronous BA. A protocol for this task was proposed by . Their construction, however, is flawed in several ways: For starters, it relies on multi-valued OCC instantiated by Canetti and Rabin's result (which, as mentioned above, only provides binary OCC). This shortcoming can be repaired by plugging in our above multi-valued OCC construction. However, as we show, even with this fix it remains unclear whether the protocol of Ben-Or and El-Yaniv achieves its goal of expected-constant-round parallel asynchronous BA, as the proof is incorrect. Thus, as a second contribution, we provide a simpler, more modular protocol for the above task. Finally, and as a contribution of independent interest, we provide proofs in Canetti's Universal Composability framework; this makes our work the first one offering composability guarantees, which are important as BA is a core building block of secure multiparty computation protocols.

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Revisiting asynchronous fault tolerant computation with optimal resilience

Cited by 4 publications

References 13 publications

Perfectly-Secure Synchronous MPC with Asynchronous Fallback Guarantees

Perfectly-Secure Synchronous MPC with Asynchronous Fallback Guarantees

Revisiting the Efficiency of Asynchronous Multi Party Computation Against General Adversaries

Concurrent Asynchronous Byzantine Agreement in Expected-Constant Rounds, Revisited

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