Three Attacks on Proof-of-Stake Ethereum

TL;DR

This paper refines and combines attacks on Proof-of-Stake Ethereum, demonstrating that adversaries with minimal stake and limited network control can cause significant consensus disruptions, threatening protocol security.

Contribution

It introduces more severe variants of existing attacks and a new combined attack that requires minimal stake and no network control, highlighting increased vulnerabilities in PoS Ethereum.

Findings

Refined attacks relax adversarial stake and timing requirements.

Combined attack enables long-range reorganizations with minimal stake.

Potential for protocol destabilization and incentive misalignment.

Abstract

Recently, two attacks were presented against Proof-of-Stake (PoS) Ethereum: one where short-range reorganizations of the underlying consensus chain are used to increase individual validators' profits and delay consensus decisions, and one where adversarial network delay is leveraged to stall consensus decisions indefinitely. We provide refined variants of these attacks, considerably relaxing the requirements on adversarial stake and network timing, and thus rendering the attacks more severe. Combining techniques from both refined attacks, we obtain a third attack which allows an adversary with vanishingly small fraction of stake and no control over network message propagation (assuming instead probabilistic message propagation) to cause even long-range consensus chain reorganizations. Honest-but-rational or ideologically motivated validators could use this attack to increase their profits or stall the protocol, threatening incentive alignment and security of PoS Ethereum. The attack can also lead to destabilization of consensus from congestion in vote processing.