Recently, two bitcoin cash (BCH) pools launched a 51% attack on this blockchain, apparently to reverse a miner's trade.
This move is related to the hard fork of the BCH network on May 15. The two tanks, BTC.com and BTC.top, took this action to prevent unknown miners from taking away coins that did not belong to them after the code was changed. On the same day, the attacker used a bug that was not related to the upgrade (which was later fixed). This bug caused the network to split and the miners could dig out empty blocks in a short time.
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In a cryptocurrency environment like BCH, 51% of attacks require an entity or organization to control most of the computational power, allowing them to perform things that are usually not done and are not allowed, such as trying to rewrite the transaction history of the network. .
This has always been a controversial topic, and some currencies have suffered similar attacks due to the decline in computing power in the network.
BTC.top's computing power has indeed exceeded 50% in a short period of time, but BTC.com and BTC.top can unite to reverse transactions in the block.
However, the interesting thing about this special attack against BCH is that the purpose of implementing this attack can be said to be something that is ubiquitous to the community, not to reward the attacker, nor to make money Have it.
But not all BCH community members agree with this. A BCH developer named moniker Kiarahpromises wrote in an article on May 17:
"Restructuring to restore unknown transactions, this is 51% of attacks. Probably the worst attack. As mentioned in the white paper. Say good (miners and developers) decentralized and anti-censorship cash? How is it convenient?"
The internal details of this attack (and the attack that caused the attack) initiated by the pool are complex.
Bitcoin podcast host Guy Swann explained on Twitter:
“Since the birth of BCH in 2017, a large number of coins have been accidentally sent to the address “anyone can consume” (due to the transaction compatibility of signatures, but BCH does not support SegWit), or they may be re-used from the Bitcoin network. Sent to the BCH network."
But he added that in the hard fork of BCH on May 15, once a code change was deleted, the coins could be spent, "basically the miners were handed over to the miners."
An unidentified miner attacker decided to take the coins. At this time, BTC.top and BTC.com suddenly intervened and reversed these transactions.
“When the unidentified miner tried to take the coins by himself, it was discovered by BTC.top and BTC.com and immediately decided to reorganize and delete these (transactions), support their own (transactions), use the same P2SH coins. ""
There are also some BCH users who think this is the right approach.
BCH supporter Jonathan Silverblood said:
"This is a very unfortunate situation, but it is also a manifestation of the workload. The miners did choose to give up the high computing power, but as far as I know, this is because they think one of the transactions is invalid. ""
However, some people think that this is not a good thing for BCH, they think this incident shows that this cryptocurrency is too central.
The 51% attack has become a common concern for the PoW currency (as mentioned above, due to the decline in computing power, some blockchains have had to face this problem). At present, half of Bitcoin's computing power is in the hands of three mining pools.