Earlier today, IOHK presented its checkpointing proposal to the Ethereum Classic (ETC) community. This is meant as a short-term solution for preventing future 51% attacks. In the past several weeks, the network has suffered a number of such attacks, which has cast doubt on ETC’s future. One of these attacks cost OKEx $5.6 million. In the wake of these problems, several exchanges increased validation times for ETC transactions. 

Checkpointing consensus. Source: IOHK presentation.

As its name would imply, the solution proposes the introduction of checkpoints that would validate the network. Thus if an adversary were to mine a “shadow” network (as previous attackers did when they managed to double-spend funds on OKEx), this shadow network would not have those validating checkpoints. Therefore, while they may have more proof-of-work than the main network, it will not be accepted.

Checkpointing would be performed by an unspecified Ouroboros Byzantine Fault Tolerant, or OBFT, checkpointing network and signed on the ETC by ‘trusted members’. The checkpoints would be inserted on average every three blocks.

The proposal does not specify who would be chosen as trusted members, but if accepted, a heated debate is likely to ensue over the selection. OBFT consensus is also used by Cardano (ADA). We asked the presenters if Cardano could be used instead of creating a new checkpointing network. They said that this is possible and that Bitcoin (BTC) could also be used for this purpose. As to the general question of the size of the checkpointing network, they said:

It still needs to be defined, but it's important to know how that plays because the bigger the federation, the bigger time slots you need until you get agreement on the two-thirds of that [needed to reach consensus].

Members of the ETC community have made a number of proposals aimed at solving the existential issues faced by the network — from changing the hashing algorithm to greater regulation of hashpower marketplaces. There is no way of predicting which route the ETC will take, yet, one thing seems to be certain — if something is not done soon, the network whose mantra is “code is law” may ultimately be repealed.