Ethereum Classic respond to fearful claims of ongoing 51% attack

Ethereum Classic developers have responded to claims made by cryptocurrency exchange Coinbase regarding an ongoing 51% attack.

The definition of a 51% attack is “the ability of someone controlling a majority of network hash rate to revise transaction history and prevent new transactions from confirming.” You can read more about what a 51% attack is and what the implications are here.

The “deep chain reorganisation of the Ethereum Classic blockchain” was brought to light by Coinbase, who went on to halt transactions on the ETC blockchain as a result.

In a blog post, Coinbase continued their statement: “On 1/5/2019, Coinbase detected a deep chain reorganisation of the Ethereum Classic blockchain that included a double spend. In order to protect customer funds, we immediately paused interactions with the ETC blockchain.

“Subsequent to this event, we detected 12 additional reorganisations that included double spends, totaling 219,500 ETC (~$1.1 million).”

“As part of that commitment, we monitor blockchains for activity that could be harmful to our customers and take prompt action to safeguard funds. We want to emphasize to customers that Coinbase strives to be the most trusted and safest place to buy, sell, or store cryptocurrency.”

Officials at Ethereum Classic were quick to respond to Coinbase’s initial statement, stating that the exchange had not approached ETC regarding the attack, which is “still very much an ongoing process.”

Ethereum Classic then tweeted out that the issue was due to “selfish mining” and not a 51% attack. They went on to claim that “double spends” had “not been detected.”

However, they admitted that both ETC and Coinbase’s version of events could be true, tweeting: “To be clear, we are making no attempt to hide or downplay recent events. Facts are facts, and as the situation develops, we’ll soon get a full picture of what actually took place. Linzhi is testing ASICs. Coinbase reported double spends; both may be true. In time, we will see.”

According to crypto51app, the hourly cost of a 51% attack on the Ethereum Classic blockchain would be $4,712.

The attack has sent shockwaves across the cryptocurrency community, with Bitfly writing that they have “temporarily increased block confirmations on our ETC mining pool,” before going on to confirm “that there was a successful 51% attack on the Ethereum Classic network with multiple 100+ block reorganization. We recommend all services to closely monitor the chain and significantly increase required confirmations.”