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BFT Protocol Forensics

Publication ,  Conference
Sheng, P; Wang, G; Nayak, K; Kannan, S; Viswanath, P
Published in: Proceedings of the ACM Conference on Computer and Communications Security
November 12, 2021

Byzantine fault-tolerant (BFT) protocols allow a group of replicas to come to consensus even when some of the replicas are Byzantine faulty. There exist multiple BFT protocols to securely tolerate an optimal number of faults t under different network settings. However, if the number of faults f exceeds t then security could be violated. In this paper we mathematically formalize the study of forensic support of BFT protocols: we aim to identify (with cryptographic integrity) as many of the malicious replicas as possible and in as distributed manner as possible. Our main result is that forensic support of BFT protocols depends heavily on minor implementation details that do not affect the protocol's security or complexity. Focusing on popular BFT protocols (PBFT, HotStuff, Algorand) we exactly characterize their forensic support, showing that there exist minor variants of each protocol for which the forensic supports vary widely. We show strong forensic support capability of LibraBFT, the consensus protocol of Diem cryptocurrency; our lightweight forensic module implemented on a Diem client is open-sourced and is under active consideration for deployment in Diem. Finally, we show that all secure BFT protocols designed for 2t+1 replicas communicating over a synchronous network forensic support is inherently nonexistent; this impossibility result holds for all BFT protocols and even if one has access to the states of all replicas (including Byzantine ones).

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Published In

Proceedings of the ACM Conference on Computer and Communications Security

DOI

ISSN

1543-7221

ISBN

9781450384544

Publication Date

November 12, 2021

Start / End Page

1722 / 1743
 

Citation

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Sheng, P., Wang, G., Nayak, K., Kannan, S., & Viswanath, P. (2021). BFT Protocol Forensics. In Proceedings of the ACM Conference on Computer and Communications Security (pp. 1722–1743). https://doi.org/10.1145/3460120.3484566
Sheng, P., G. Wang, K. Nayak, S. Kannan, and P. Viswanath. “BFT Protocol Forensics.” In Proceedings of the ACM Conference on Computer and Communications Security, 1722–43, 2021. https://doi.org/10.1145/3460120.3484566.
Sheng P, Wang G, Nayak K, Kannan S, Viswanath P. BFT Protocol Forensics. In: Proceedings of the ACM Conference on Computer and Communications Security. 2021. p. 1722–43.
Sheng, P., et al. “BFT Protocol Forensics.” Proceedings of the ACM Conference on Computer and Communications Security, 2021, pp. 1722–43. Scopus, doi:10.1145/3460120.3484566.
Sheng P, Wang G, Nayak K, Kannan S, Viswanath P. BFT Protocol Forensics. Proceedings of the ACM Conference on Computer and Communications Security. 2021. p. 1722–1743.

Published In

Proceedings of the ACM Conference on Computer and Communications Security

DOI

ISSN

1543-7221

ISBN

9781450384544

Publication Date

November 12, 2021

Start / End Page

1722 / 1743