A few weeks ago, a developer on Ethereum (ETH) created a lot of controversy after revealing the fact that he was working on a tool that would allow miners to reorganize the blockchain to their benefit. Although he stopped his research due to too much pressure, Vitalik Buterin and Georgios Konstantopoulos have just published a paper explaining how Ethereum 2.0 would make such a move impossible.
Reorg as a service: the heated debate
On July 9, the developer @EdgarArout set Twitter ablaze after publishing a surprising tool he was working on. In practice, it would allow miners to adopt a modified version of the Ethereum client. The latter could then accept bribes to perform a short reorganization of the chain.
This tool can have several uses. Initially, users practicing arbitrage could ensure that trade is profitable. However, this service would also allow malicious users to attack DeFi protocols, a trend that is already far too prevalent on Ethereum to play around with.
Furthermore, this proposal presents several dangers to the blockchain itself. It could remove the immutability of Ethereum and cause heavy slowdowns in the validation of transactions.
On July 15, the latter finally decided to abandon his project in the face of growing pressure from the community. However, this does not prevent another similar project from being developed, although it has not been formalized.
“The mev-reorg idea is shelved for now (private repo) – the pressure to stop and the threats were too much of a burden and it wouldn’t be fair to my family to have to deal with it all.”EdgarArout’s Twitter post
The problem of too frequent reorgs
On July 20, a few days after @EdgarArout’s announcement, Ethereum co-founder Vitalik Buterin, along with developer and researcher Georgios Konstantopoulos, published a paper explaining how the move to proof of stake (PoS) would make such behavior impossible.
In practice, chain reorganizations are not harmful to the network, if they occur occasionally. Indeed, they can occur due to latency problems, when 2 miners can validate a block simultaneously. However, the network would be in danger if they were to become commonplace.
“In the worst case, frequent reorgs can completely nullify the settlement guarantees of a blockchain and prevent it from progressing.”Publication by Vitalik Buterin and Georgios Konstantopoulos
How does PoS solve this problem?
In a proof-of-work (PoW) blockchain, as is currently the case on Ethereum, blocks are solidified serially. This means that when a block is mined, a single competing block can take its place and reorganize the chain. A few seconds later, when a second block is mined, a chain of 2 competing blocks is needed to reorganize. Thus, as more blocks are mined, the difficulty of reorganizing the chain increases until it becomes impossible to reorganize the first block.
In the case of PoS which will be used by Ethereum after “The Merge”, the validation of blocks and their addition to the chain are managed by 2 entities:
- The proposer: who proposes the block;
- The attestors: a group of validators who vote for the block they consider to be the head of the chain.These attestors are chosen randomly in the form of a committee made up of 1/32nd of the validators.
“Today, the beacon chain has ~196,000 validators, which means that each block has a committee size of ~6,125. As a result, even single-block reorganizations are extremely difficult, as an attacker controlling only a few validators has no way to defeat the honest majority of thousands of attestors.”Publication by Vitalik Buterin and Georgios Konstantopoulos
Indeed, impossible in this case to make a bribe for all members of the committee.
While waiting for the merger of Ethereum 1.0 with Ethereum 2.0 and the transition to the Proof of Stake at the end of the year, the Ethereum network will deploy the hard fork London on August 4. This hard fork will integrate the EIP-1559 and will probably stir up once again the debates.