Coinbase published a blog post revealing a deep chain reorganization attack with double spend on ETC totaling to 219,500 of the coins equivalent to approximately $1.1 million
On 5 January 2019, Coinbase temporarily ceased on-chain ETC transactions following the discovery of a 51% attack. The exchange found eight more attacks subsequent to the first discovery with a sum of 88,500 ETC or $460,000 in double spend. In the latest update, 12 more deep chain reorganization attacks was detected carrying a total of 219,500 ETC or $1.1 million in double spend.
Though the initial discoverer of the attack, the exchange emphasized they are not the objective of it. As of yet, there is no information on whom the attack is targetting.
User funds are secure and Coinbase, currently assessing the security of reinstating ETC transactions, will give updates on the status of ETC support.
A Response from Ethereum Classic Team
Ethereum Classic replies to Coinbase through Twitter saying, the exchange neglected to inform the ETC team before running the blog post.
To be clear we are making no attempt to hide or downplay recent events.— Ethereum Classic (@eth_classic) January 7, 2019
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. https://t.co/bbq6eqIoiS
A Laconic on Double Spend
An attack such as the 51% attack or deep chain reorganization is not easy to execute, especially against networks with huge market capitalizations. But the opposite is true for coins with lesser capitalization. It requires the perpetrator to gain the greater share of a network’s hashrate; the longest chain. The attacker will then be able to tamper the ledger, thus, restructuring the blockchain. The attacker is then able to do double spend by reversing previously confirmed transactions.
Small-cap cryptocurrencies like Bitcoin Gold (BTG), Litecoin Cash (LCC), Verge (XVG), Vertcoin (VTC), and ZenCash (ZEN) encountered such an attack to their protocol in 2018. The difference between the ETC incident and those from last year is that ETC is among the top-20 of the largest cryptocurrencies in the market.