Chain-based consensus
PoW
PoS
Iddo Bentov, Ariel Gabizon (Technion) and Alex Mizrahi (chromaway.com)
Rafael Pass Elaine Shi (CornellTech/Cornell, IC3)
AsiaCrypto'17
Resilient assuming only that a majority of the online players are honest
Phil Daian Rafael Pass Elaine Shi (CornellTech/Cornell)
FC'19
Using sleepy consensus at its core
Money-does-not-switch-hands-too-quickly assumption (Section 3.1)
Not deposit-based
Adopt fruitchain to achieve incentive compatiblity (ε Nash equilibrium)(e.g. prevent long range attack)
Semi-adaptive security (corruptions with delay)
Penalize nothing at stake (i.e. players that sign multiple blocks with the same timestamp)
Ouroboros
Erica Blum, Aggelos Kiayias, Cristopher Moore, Saad Quader, and Alexander Russell
SODA'20
Bitcoin guarantees consistency with error$ 2^{−k}by removing$ O(k)blocks
Improves the length of this suffix of Snow White and Ouroboros from$ \Theta (k^2)to$ \Theta (k)
Aggelos Kiayias, Saad Quader, and Alexander Russell
Improve the security threshold by re flecting for the first time the positive effect of rounds with concurrent honest leaders
In Ouroboros Praos and Genesis: the probability of a uniquely honest round exceeds that of the other two events (adversarial round and concurrent honest leaders round) combined
In Sleepy Consensus and Snow White: a uniquely honest round is more likely than an adversarial round
Improve The combinatorics of the longest-chain rule: Linear consistency for proof-of-stake blockchains
Number of confirmations
"Nakamoto-PoS"
Xuechao Wang, Govinda Kamath, Vivek Bagaria, Sreeram Kannan, Sewoong Oh, David Tse, Pramod Viswanath
Lei Fan (Shanghai Jiao Tong University) Hong-Sheng Zhou (Virginia Commonwealth University)
The latest version is not published
Vivek Bagaria, Amir Dembo, Sreeram Kannan, Sewoong Oh, David Tse, Pramod Viswanath, Xuechao Wang, Ofer Zeitouni
SBC'20
Nakamoto-PoS: update randomness every block (with VRF)
Comparison: Snow White and Ouroboros uses stabilized segment of the blockchain from a few epochs before for randomness
Asynchronous Safety
CBC Casper
Permissioned
Elaine Shi, CSF'19
A variant of Aura (Parity PoA chain)
Synchronous (lock-step), adaptive adversary
Common prefix: chop off blocks from the recent$ nrounds under$ n ≥ 3f + 1
Demonstrates that a vanila version of deterministic longest-chain protocols with round-robin cannot achieve $ f ≥ n/3
https://gyazo.com/40e8ae71eda9eddbbf13af9ae4192028
$ n = 9, f = 3
Aggelos Kiayias and Alexander Russell
Synchronous (lock-step)
Blocks in the main chain older than$ 3t + 1slots are considered finalized ($ tis the number of Byzantine nodes)
Optimistic fast confirmation
Argue that recoverbility from a network failiure (split or large delay)
Application: checkpointing of PoW blockchain