The hard fork of Bitcoin Cash happened on 15th November which is being blamed for the real reason behind the massive market crash due to the hash wars between the two parties. The hard fork was unnecessary as the new blockchain have no specific use-case that makes it different from the other. The hash wars are nothing just ego wars that are hurting the entire crypto community rather than just two people behind the war.
The hard fork has led to the introduction of a vulnerability into the BCH ABC network which exposes it to a risk of 51% attack.
The Bitcoin Cash ABC developers had to introduce a new code which changes the method through which the nodes on the network decide if a particular block is valid or not.
The previous version of BCH worked under the Proof of Work algo for block validation. The developers have now implemented checkpoints being used by miners to ensure that the work is being done on the right version of the chain.
The checkpoints were implemented to preserve the chain from attackers by using dipstick checkpoint on every 10th block. If the miners confront a block that doesn’t match the checkpointed version, they will reject it.
Eric Wall, a cryptoanalyst explained how any hacker that controls 50% of the total hashrate of the BCH blockchain will possibly submit 10 blocks together by rearranging 9 valid blocks. This attempt by the hacker for submitting the blocks at the same time as the network finding the 10th block may cause the blockchain to split. He further explained that the blockchain will then have forked into two and if there are two exchanges on different forks the attacker can sell the same cryptocurrency twice on both the exchanges earning double the amount. He said that the hacker would need just an amount less than $27000 for controlling the whole BCH ABC network.