[UPDATED] Ethereum Classic Hit By 51 Percent Attack


The network has asked exchanges and mining pools to up confirmation times on transactions.

UPDATED | January 7, 2019 (20:35 UTC):

Coinbase has claimed it noticed “a deep chain reorganization of the Ethereum Classic blockchain that included a double spend” on Saturday, January 5. Mark Nesbitt, writing on the exchange’s blog, says there have been eight more reorganizations with double spends – worth over 88,000 ETC (around $460,000) – on the network. It’s unclear whether Coinbase alerted Ethereum Classic, which, as of January 6, said the network appeared to be “operating normally.”

ORIGINAL | January 7, 2019: 

Bitfly, which operates the Etherchain block explorer and Ethernodes node explorers as well as an ETC mining pool, has confirmed that the Ethereum Classic network has been hit with a 51 percent attack. With at least 51 percent of the network’s hashpower, an attacker is able to put their own (longer) chain on the network and “reorganize” the blockchain. There are multiple malicious strategies available to a person or persons with 51 percent of a network’s hashpower, double spends being one of them.

CoinNess, an apparently China-based coin journal that claims funding from Huobi Global, ZhenFund, and FreesFund, first reported late on January 6 that SlowMist – a blockchain security company, also in China – had warned that the Ethereum Classic network might be experiencing a 51 percent attack.

Through its Twitter account, Ethereum Classic pointed to the BlockScout block explorer and responded, “From what we can tell the ETC network is operating normally.”

Fewer than eight hours later, the ETC network began seeing things differently. It asked “all exchanges and mining pools [to] please allow a significantly higher confirmation time on withdrawals and deposits [+400].”

Shortly thereafter, without confirming the attack had indeed taken place, it retweeted a CoinNess article citing exclusive information from SlowMist that a private mining pool had seized 51 percent of the network’s hashrate.

The address at the root of the speculation, which begins with 0x3ccc8f74, has been mostly silent for the last 12 hours after it mined block 7,256,171.

Bitfly says it has increased block confirmations on its Ethereum Classic mining pool due to the reorg attack. At 19:22 UTC, Kraken announced it has increased confirmations for ETC deposits on its exchange from 120 to 500, meaning it will take nearly two hours for Classic transactions to be confirmed.

This article is being updated as more news is available.

Jeff Benson is Managing Editor of ETHNews. He’s worked as a writer and editor everywhere from Sudan to Reno. He holds a bachelor’s in politics from Willamette University and a master’s in nationalism studies from University of Edinburgh. When he’s not in the newsroom, he trots the globe and writes about it. He holds a bit of value in ETH.

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