As it is known, cryptocurrency is supposed to guaranteed, that no one can spend the same coin twice. Every transaction ever made with Bitcoin, is recorded in a database that anyone can access. The database is called blockchain and its supposed to keep everyone honest.
However, Coinbase has publicly announced through a blog post that they have detect “Deep Chain Reorganization Detected on Ethereum Classic (ETC)” and therefore they will paused interaction with the ETC blockchaing. They also added, that apart from this, another 12 additional reorganizations that included double spends, totaling 219,500 ETC (~$1.1M).
As of now, the trading is still paused while Coinbase is further investigating the major cause and it has not announced when exactly the trading will resume.
According to Coinbase security engineer Mark Nesbitt’s blog post, the attackers could spend coins twice because of what’s called a 51 percent attack. To do this, attackers took control of more than half of the processing power that computes and stores the Ethereum Classic blockchain. That let the attackers create alternative transactions for some coins, essentially spending them twice.
A Twitter account for Ethereum Classic said it had detected a problem but didn’t think it was a 51 percent attack and hadn’t seen signs of “double spending” coins. ”
The coins that attackers allegedly spent twice were worth about $460,000, Nesbitt wrote. He added that potential for an attack like this one is a problem faced by all cryptocurrencies, and doesn’t mean Ethereum Classic was especially vulnerable.
