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.
Authors
Caspar Schwarz-Schilling, Joachim Neu, Barnabé Monnot, Aditya Asgaonkar, Ertem Nusret Tas, David Tse