A lot of discussions have been ongoing lately surrounding the occurring of suspicious mining related to Ethereum Classic (ETC). The discussions follow the announcement made by Coinbase, a major crypto exchange, stating that the platform detected “chain reorganizations” and double spends on the ETC blockchain. The activities were defined to be a 51% attack on the blockchain.

Many crypto users further discussed the possibility of 51% attacks on other cryptocurrencies that utilize Proof-of-Work (PoW) algorithm. Some tweeted their opinions stating that a cryptocurrency must be susceptible to a 51% attack to be considered decentralized, among them included Litecoin (LTC) creator Charlie Lee.

Bitcoin (BTC) being the largest cryptocurrency which uses PoW algorithm became a highlight in discussions on whether it may face similar attacks. Satoshi Sakamoto, the unknown creator of BTC and author of the bitcoin whitepaper, stated in it that an honest chain will grow fastest compared to other competing chains and outpace them if honest nodes control a majority of CPU power. An attacker would have to redo Proof-of-Work of a certain block and all other blocks that come after it to modify a past block. Moreover, the modifier would then need to catch up and exceed the progress of the honest nodes.

Therefore, it is significantly difficult to attack the BTC blockchain. A core developer of the currency named Jimmy Song tweeted that a “51% attack on BTC is really hard”. He stated that there are several aspects to consider attempting the attack, including the obtaining of 51% total hashing power through mining equipment that consume an enormous amount of electricity. He further elaborated that the required conditions will be harder to obtain as time progresses.

To put it simply, the security of blockchains utilizing PoW algorithm relies on the honesty of miners. If over 50% of miners follow the instructions and rules set by the whitepaper and other regulations, the blockchains will be safe from attacks like a 51% attack. However, some people see the dependency on miners’ honesty as a vulnerability for PoW-based digital currencies.

The creator of Ethereum (ETH), Vitalik Buterin, also voiced out his concerns regarding attacks on blockchain on Twitter. He stated that ETH’s large structure is the reason why it has not been attacked yet. He further elaborated that the 51% attack on ETC shows that it is possible to perform a 51% attack on “fairly large chains” and the PoW mechanism might be vulnarable to similar attacks in the future.