Lightning Strikes Twice: Etherium Classic Network Rollback due to 51% Attack

Ethereum Classic sustained a 51% attack last weekend, the second attack in less than two years.

Primary investigations at the time revealed no indication of double-spending

ethereum classic etc
Ethereum Classic (ETC) price drops after reports of a 51% attack. (Source:

Ethereum Classic (ETC) price falls after news of a 51% attack. 

Nevertheless, almost a week on, additional investigations have exposed that the hacker managed to double-spend 807,206 ETC ($5.6 million) across two days.

As per data analysis reported by Bitquery, the intruder injected 11 transactions into the re-organized chain. They also perceived that the attacker utilized just 17.5 BTC ($192k) to obtain the hashing power required to split the chain.

log of ethereum classic transactions into the re-organized chain

Who said lightning doesn’t strike twice?

This is not the first time that Ethereum Classic has had a cyber attack. In January 2019, criminals made a 51% attack to double-spend 219,500 ETC ($1.1 million).

The range of the weekend crime is much more extensive than the recent attack. This sends numerous to doubt the viability of the project going forward.

In a report posted in May 2018, “The Realistic Lucrative Case of Ethereum Classic attack — Today,” analyzed the cost to 51% attack the Ethereum Classic network.

To come to an assessment, the author used the formula:

Total Network Hashrate / Efficient Miner Hashrate = Miner Units neededMiner Units needed * Miner Unit Cost + Electricity = 51% Attack cost

The network hash rate averaged 7000 GH/s in 2018, while the miner hash rate for an Antminer E3 was 0.18 GH/s.

Hence 38,888 Antminer E3s were required, priced at $2,150 each, plus $150k per day for electricity, equating to an anticipated cost to attack the ETC network of $85 million.

As of 2018, the hash rate on the Ethereum Classic network has considerably decreased. Today, it’s about the 4000 GH/s mark.

Ethereum Classic hash rate

Furthermore, miners have displayed much more efficient in recent times, with Bitmain’s Antminer S19 Pro able to hash 110 TH/s.

Decreasing network hash rate, and increasing miner efficiency meant Ethereum Classic was ripe for attack.

Possible Rollback for Ethereum Classic

Resuming from this will be challenging as security is the grounds of any severe blockchain.

At the same time, immutability should determine what’s done is done.

Nevertheless, Binance CEO, Changpeng Zhao (CZ) tweeted that he received an alert that Ethereum Classic is trying a network rollback to shift the attack.

Ethereum Classic appeared about due to a community split on how to deal with a $50 million theft from a developer app on the Ethereum blockchain.

Some investors wanted to roll the network back to return the Ether to the lawful owners; others considered that one of the primary tenets of cryptocurrency is irreversibility.

In 2016, Ethereum endured a hard fork to modify the code and revert the hack. At the same time, Ethereum Classic moved on as it was.

If CZ’s alert is perfect, it would be moderately ironic that Ethereum Classic developers chose to roll the network back.

Either way, core developers need to contemplate long term approaches to defend the network.

Unless it won’t be long before we discover the third attack.

Leave a Comment

Leave a Reply