Finality Gadget
Joachim Neu and Ertem Nusret Tas and David Tse (Stanford)
Casper FFG
Adopted in Ethereum 2.0
GRANDPA
Block production mechanism is BABE inspired by Ouroboros Praos in GRANDPA, different voters can cast votes simultaneously for blocks at different heights
GRANDPA only depends on finalized blocks to affect the fork-choice rule of the underlying block production mechanism
Nightshade Finality Gadget
Doomslug: + Nightshade Finality Gadget (NFG)
Afgjort
Bernardo Magri (Aarhus University), Christian Matt (Concordium), Jesper Buus Nielsen and Daniel Tschudi
SCN'20
Define desired properties for finality layer called (∆, k)-finality: Chain-forming, Agreement, Δ-Updated, k-support
Partial synchrony (unknown$ \Delta_\mathrm{net}) with gossip network
Perform Weak Multi-Valued Byzantine Agreement (, which is reduced to a binary, randomized & graded Byzantine agreement) on blocks to finalize
Dynamically adjust the depth (to keep up with the chain growth) and the number of the prefix
Assume 1. bounded dishonest chain growth or 2. allow dishonest chain to be finalized and make a rollback (i.e. 1-support)
Non-incentive-wise argument on long-range attack (4.1)
UC proof sketch (Section 4.2)