Vitalik Buterin downplayed Ethereum’s recent close call with a finality loss, arguing that minor delays are okay as long as the wrong block isn’t finalized. Most experts agree with this.
Vitalik Buterin, one of the founders of Ethereum, says that the network can afford to lose finality occasionally without putting it in serious danger. This is true even after a recent client fault almost broke the blockchain’s confirmation mechanism.
Buterin noted in an X post that “there’s nothing wrong with losing finalisation once in a while” after a flaw in the Prysm Ethereum client. He went on to say that finalisation means the network is “really sure” that a block won’t be changed.
Buterin said that if finality is delayed for hours because of a big flaw, “that’s fine,” and the blockchain maintains running while that happens. He added that the real issue will be different: “The thing to avoid is finalising the wrong transaction.”
Ethereum vs Bitcoin: Understanding finality
Fabrizio Romano Genovese, who has a PhD in computer science from the University of Oxford in England, is a partner at the blockchain research startup 20squares and an expert on the Ethereum protocol. He agreed with Buterin. He added that Ethereum is more like Bitcoin BTC$92,626 when it loses its finality. He also said that Bitcoin has had “no finality since 2009 and no one complains.”
A proof of work Bitcoin’s blockchain, for example, can split into several chains. The one that gets the most effort (typically the longest) is the one that is regarded authentic. But if a second branch develops big enough to take over the primary branch, it makes the main branch and the transactions it held worthless.
This is how Bitcoin works: its finality is based on chance, not certainty. This is because, even though it is almost impossible when enough blocks are added to the main branch, a reorganization might still happen in theory. Genovese talks about how Ethereum is different since it has rules that make blocks “final.” Ethereum has a way to finalise things: a block is “justified” when it gets more than 66% of the validator’s votes. If more than two epochs (64 blocks) have passed, the block is definitive.
This isn’t just a theory; it happened in May 2023 because of an event that was identical to the recent one with the Prysm client. Genovese claimed that these events don’t make the chain less secure. Instead, “it just means that our guarantees around reorg have temporarily gone back to being probabilistic and not deterministic.”
Effects on Ethereum sidechains and bridges
Lack of finality would hurt infrastructure that depends on it, such as some inter-blockchain or layer-2 (L2) bridges. A spokesperson for the Ethereum sidechain Polygon informed that Polygon would keep doing business as usual, but transfers from Ethereum to the sidechain “may be delayed while waiting for finality.”
The Polygon representative also indicated that the crosschain settlement layer AggLayer will hold up transactions from Ethereum to L2 until finality was attained again. They nonetheless maintained that “there is no scenario in which users experience a rollback or message invalidation” because of a lack of finality:
The only real effect of a delayed finality event is that deposits may take longer to show up. Users won’t see any reorg-driven reversions after this delay. Genovese attributed these delays to developers who require finality. He ended with, “If a bridge builder decides not to put in a backup plan in case of loss of finality, that’s their choice.”