Before I start with the Vertcoin attack, I want to give a short summary of the BCH war
ABC stoped fighting, SV still trying
As predicted here ABC has reduced hashpower to the level where mining is profitable. Their hashpower is slightly below SV but they are still well ahead in PoW. At this rate the SV chain has no real chance of winning Nakamoto consensus, while just burning money. SV mining is not profitable and driven by ideologic attackers (even though I have no idea what they hope to achieve at this point.)
[from https://cash.coin.dance/]
As a result SV mining is highly centralised by few ideologic actors, while ABC mining shows a variety of small pools putting some hash power for profits.
[from https://cash.coin.dance/]
At this point the war should be over, ABC is not even defending any longer since the desperate attack by SV is not threatening. The open war is officially over.
Vertocin 51% attack
Much more exiting, there has been a 51% on vertcoin, double spending about 100.000$. And any small PoW chain in fact lives in the constant danger of such attacks.
What is interesting to study will be the reaction of vertcoin and learn for eventual future attacks on bigger chains.
Accept and move on
This seems to be what they are doing and quite interestingly the price seemed to not care about the attack and fell just like other cryptos. Maybe investors have not yet realised and there is little real money in this project?
[from coinmarketcap.com]
But there would be many things that can be done to fight this attack
Censor attack the dishonest miners
The honest miners may collaborate to censor the attackers. They may be mining a minority chain, but it is unlikely that the attackers are willing to support their attack for extended amounts of time. They simplu hope that the miners will eventually accept their chain and mine it, but why should honest miners stolen their mining rewards do that?
Eventually the real chain will overtake and the double-spends reverted. The important thing for this to work is that the censor attempt needs to be announced quickly and people should stop transacting on the new chain as otherwise there will be another set of double spends when the old chain comes back. Once the attackers leave the chain with their gained capital it can no longer be reversed.
Fork the chain
In theory this can still be done after a failed censoring defence. The chain is forked by checkpointing out the dishonest attack. Many people will think that this is not a viable defence, but I think this will be crucial in the future to deter attackers from even trying. So I hope to see this done in practice and if I would be in the vertcoin community I would just do it myself.
Miners are just service providers, they are not in controll. The people really in controll are the stakeholders. A fork is nothing but letting them choose what they want to support. Instead of vertcoin, they will now have scammycoin and vertcoin2. One coin has lots of double-spends the second is in a state where this attack never even happened.
Every stakeholder can now decide. Do they not care and hold both, or do they sell one for the other? Since the inverstors are supporters of vertcoin, it is very predictable how they will choose. Why would they value a coin created by attackers that scams people of their funds. The value proposal of that chain is very low. The scammycoin fork will quickly move to a value close to zero and vertcoin2 will succeed vertcoin. The attack then never happened because the miners did not act in the interest of the stakeholders and their blocks are simply rejected. They only burned some electricity and now have nothing to show for.
PoW is a great way to find consensus in the simple cases. But when it comes to big conflicts every coin is eventually PoS. Forks can always be made and the investors that have a stake decide the price of the forked coins. And people can mine against the stakeholders will for some time, but in the end it is the community deciding what happens, not the miners.
A similar story happened in the case ETH and ETC where a bug in smart contract was reversed by forking the chain. The miners did not decide this split, the investors did. The majority was fine reverting this bug and eth is valued much higher than etc (to be honest, at the current time the projects have taken very different patches in development and the price is no longer about this event).
Many people claim that this should not be done, but they are mistaken. Forks are not a dirty trick, they are an important tool to resolve conflicts without involving a central party. They exist and we can use them. I am a supporter of the ETC side, thinking that code should be respected especially since these forks put an advantage for big developers as ETH will never fork for the bug of an average user, but I have no right to impose that view on everyone. I still have my ETC and others can have their more governed ETH. Now the communities have also split. It is very unlikely we see any such forks on ETC in the future since the ETC supporters share that mindset.
While the choice was quite decisive in the ETC-ETH case I think it would be even clearer when forking to discard malicious mining attacks. Even me as a ETC supporter would not try to use my stake to protect people trying to destroy crypto for their private gain. ETC had a real value proposal, make truly uncensorable smart contracts. What is the value proposition of scammycoin? Do not use the possibility to use PoS votes to replace PoW mining in special cases? Why not use all the options that are available? Especially after the fork Vertcoin2 will have the people committed to deflect malicious mining attackers using all tools that are decentralised while scammycoin is held only by people that accept such attacks. Guess which coin will be targeted by attackers in the future.
To sum up, forks are a valid tool that may be crucial to protect PoW chains against illicit mining attacks. I hope to see this implemented on some smaller chains so we know how this plays out in practice.