Autres en vidéo

Apéro Defi #4

par Finance Innovation

Yackolley Amoussou-Guenou (CRED, Université Paris-Panthéon-Assas) An overview of blockchain consensus protocols. The proof-of-work, and many forms of the proof-of-stake Blockchains are distributed ledgers that aim to offer transparency, integrity and many other advantages over their centralized counterparts. The blockchain philosophy and technology have raised a number of interesting questions among the general public and the research community. New steps in digital finance, more cross-disciplinary research, etc. The blockchain network is autonomous and decentralized, and it must be ensured that participating nodes agree on valid transactions, and in their order. These agreement mechanisms are called consensus protocols. These protocols are run by many users to avoid centralization, while maintaining the blockchain. In this presentation, we will give a general overview of the consensus algorithms used in blockchains. More importantly, we will focus on the two consensus protocols most widely used in blockchain networks: Proof of Work (PoW) and Proof of Stake (PoS). Ulysse Pavloff (CEA-List, Université Paris-Saclay) Ethereum Proof-of-Stake and the Probabilistic Bouncing Attack Ethereum has undergone a recent change called the Merge, which made Ethereum a Proof-of-Stake blockchain shifting closer to BFT consensus. Ethereum, which wished to keep the best of the two protocol designs (BFT and Nakomoto-style), now has a convoluted consensus protocol as its core. The result is a blockchain being possibly produced in a tree-like form while participants try to finalize blocks. We categorize different attacks jeopardizing the liveness of the protocol. The Ethereum community has responded by creating patches against some of them. We discovered a new attack on the patched protocol. To support our analysis, we propose a new high-level formalization of the properties of liveness and availability of the Ethereum blockchain, and we provide a pseudo-code. We believe this formalization to be helpful for other analyses as well. Our results yield that the Ethereum Proof-of-Stake has safety but only probabilistic liveness. The probability of the liveness is influenced by the parameter describing the time frame allowed for validators to change their mind about the current main chain.