Vitalik Buterin joined in the discussion on EOS github 2 days ago. EOS seems to have a problem with the fact that their Proof of Stake algorithm lost consensus because of the conflict in the last irreversible block.
While the EOS community was discussing possible solutions to the problem, Vitalik Buterin joined to the discussion and helped to solve the issue, correctly showing that the proposed solution is unsafe with a very clean example showing the point of failure. He noted that algorithm in Casper FFG solves the problem and even explains how:
This does not seem to actually be safe. Consider a case with four validators, so we are allowed one byzantine. Suppose before time T the commonly agreed head is Z; then, at times (T, T+1, T+2, T+3), validators (A, B, C, D) make blocks extending a chain from Z. A now has votes from B, C and D and so is finalized. Now, before timeslot T+3 ends, D also (byzantine-ly) makes a block (call it D’) on top of Z. Then, at times (T+4 … T+11), (A, B, C, D, A, B, C, D) make blocks on top of D’ (this is ok because each validator is making a block at a height one higher than the block they previously made). The second A block in this chain has three votes and so is also finalized. Hence, two conflicting blocks got finalized.
In general, it’s not possible to achieve BFT safety on a block without at least two messages from most nodes that directly or indirectly reference that block; this algo tries to do it in one round and it’s likely impossible to actually do that safely. If you want an intuitive and good way of doing this, I recommend just using the algorithm in our Casper FFG paper: arxiv.org/abs/1710.09437
More recently, EOS have begun to pay more attention to some influential players, after rumors have surfaced that the EOS will replace Ethereum in the near future. Some experts even gave an alternative name to the altcoin – “Ethereum Killer“, speculating on the growth of the cryptocurrency. Although these speculations and comparisons will always be present, they sometimes create a negative network effect for their respective communities. As a by-product, these predictions triggered a chain reaction from EOS supporters, attacking Ethereum fans and vice versa.
Vitalik’s contribution to the EOS is important, as it shows that, despite the competitive nature of the two communities, the general consensus among the developers of the project is to overcome the focus on cooperation and advances in the blockchain technology problems.