LibraBFTv2: Optimistically-linear BFT Consensus with Concrete Latency Bounds

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" summary

LibraBFTv2 implements a leader-based HotStuff variant that removes probabilistic gossip and achieves optimistically-linear network complexity in the happy path while giving explicit post-GST latency bounds. It adds timeout certificate (TC) and a fast-proposal tweak that encodes highest-QC in timeouts so a proposer can both propose and finish synchronization. Incomplete broadcasts are handled by periodic pull queries; worst-case additional delay is bounded to roughly one extra timeout period (tunable via λ). A reference implementation is on GitHub.

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" chapters (24)

1. 0:00Intro
2. 1:18The HotStuff approach to State Machine Replication
3. 2:55Roadmap
4. 3:45Leaders, rounds, blocks, votes
5. 4:50Chaining blocks and QCs - Avote signs the hash of a block.
6. 5:50Commit rule - When a chain ends with 3 Cs with contiguous round
7. 7:01Safety Rules
8. 8:161-Slide Safety Proof
9. 9:23Storage and Networking
10. 10:16How about liveness? (1)
11. 10:56How to propose a block
12. 12:15How about liveness? (2)
13. 13:25How to synchronize rounds
14. 14:43Idea 1: Timeout Certificates
15. 15:56Idea 2: Opportunistic re-sharing
16. 16:44Sampling highest QCs
17. 17:39Incomplete broadcast of QCs
18. 19:20Solution: the "fast proposal" optimization
19. 21:04Incomplete broadcast of TCs
20. 24:32How about liveness? (3)
21. 25:06BFT latency of LibraBFTV2
22. 26:05Conclusion on LibraBFTV2
23. 27:14SMR security in practice: the bad
24. 27:55SMR security in practice: the ugly (3)

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