Vitalik Buterin, co-founder of the Ethereum network, downplayed the significance of the temporary loss of finality of blocks that recently occurred on the network, stating that temporary delays are considered "good" as long as the incorrect block is not confirmed, a view shared by most experts.
After a recent bug in the Ethereum client "Prysm" that nearly disrupted the transaction confirmation mechanism in the blockchain, Buterin stated in a post on X (formerly Twitter) that "there's no fault in losing finality from time to time." He added that "finality" indicates that the network is "really sure" that a particular block will not be rolled back.
Buterin explained that if "finality" is delayed for hours due to a major bug, "that's okay," and the blockchain will continue to operate during that time. He emphasized that the real problem to avoid is "confirming the wrong thing."
Expert opinion on loss of finality
Dr. Fabrizio Romano Genovese, who holds a PhD in Computer Science from the University of Oxford and is a partner at the research firm "20squares," agreed with Buterin's opinion.
Genovese pointed out that when finality is lost, Ethereum resembles Bitcoin (BTC), explaining that Bitcoin "has not had deterministic finality since 2009 and no one complains."
How does Ethereum differ from Bitcoin?
* Bitcoin (Proof of Work): It relies on probabilistic finality. The chain can split into multiple branches, and the branch that receives the most work (usually the longest) is considered valid. Although it is nearly impossible for a reorganization to occur after enough blocks have been added, it is still theoretically possible for a secondary branch to overtake the main branch (Reorganization).
* Ethereum (Proof of Stake): It has a deterministic finality mechanism. When a particular block receives more than 66% of validator votes, it becomes "Justified." And when more than two epochs (64 blocks) pass, the block becomes "Finalized."
Genovese clarified that incidents of losing finality (which also occurred in May 2023) do not make the chain insecure; rather, they "temporarily reduce our guarantees about reorganization to be probabilistic instead of deterministic."
The consequences for Layer 2 networks (L2) and bridges
Genovese noted that the loss of finality will affect the infrastructure that relies on it, including some bridges between blockchains or Layer 2 networks (L2).
A representative from the Polygon sidechain confirmed that the network will continue its operations normally, but transfers from Ethereum to the sidechain "may be delayed while waiting for finality to be restored."
Additionally, the cross-chain settlement layer AggLayer in Polygon will delay transactions from Ethereum to L2 networks until finality is restored. However, there is no "scenario in which users face rollbacks or invalidation of messages" due to loss of finality.
The practical impact is simply that deposit transactions may take longer to appear.
In conclusion, Genovese held developers who require finality responsible for any significant delays, stating, "If a bridge developer decides not to implement any backup mechanism in case of loss of finality, that is their choice."
