Ethereum Classic Experiencing 51 Percent Attack, Immutability Violated 🚨 This article is 5 years old...
Ethereum Classic Experiencing 51 Percent Attack, Immutability Violated
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Updated: Jan. 7, 2019 at 6:21 pm UTC
Cover art/illustration via CryptoSlate. Image includes combined content which may include AI-generated content.
Ethereum Classic experienced a vicious 51 percent attack that allowed attackers to conduct eleven deep chain reorganizations and double-spend 88,500 ETC, worth over $400,000. In response to the attack, the price of ETC has plummeted and services using the cryptocurrency have halted.
On Jan. 5th at 13:27 UTC, Ethereum Classic was reorganized at block 7245623, and over the course of the next three days the intensity of these attacks increased as the cryptocurrency’s immutability was violated.
Bitfly, Coinbase, Poloniex, and Kraken have all made announcements confirming the attack. Many exchanges and platforms have halted ETC-related services until the attacks subside.
Coinbase detected eleven distinct deep chain reorganizations, nine of which facilitated double-spends. Based on the exchange’s estimates, the attackers were able to double-spend 88,500 ETC, worth over $400,000.
That said, the price of ETC is rapidly dropping in response to the attack, losing 10 percent of its value in the last 24 hours. Over the course of the attack, Ethereum Classic went from $5.50 to $4.90 per coin.
The attacker has been identified. Within the last day, the attack stopped on Jan. 7th, at 05:30 UTC when the attacker’s control of total mining power fell below 50 percent, but the situation may be temporary:
If the attacker is able to regain over 50 percent of the network’s mining power, then the attacks may once again continue.
51 Percent Attacks and Reorganizations Explained
An attack can occur when one miner is able to amass 50 percent of the hashing power, allowing that miner to ‘outvote’ honest miners. This means that the attacker could statistically maintain the longest chain and determine which transactions to include on the blockchain.
This invalidates one of the issues the blockchain solves under normal conditions—double spending—where a user spends the same cryptocurrency multiple times.
It is likely that the attacker mined privately for some time before revealing the longer chains. In this case, everything on the Ethereum Classic blockchain would look normal. Then, the miner suddenly goes online and publishes a long string of valid blocks and invalidates a large number of transactions (called a ‘reorganization’ or ‘reorg.’), replacing the old segment of the chain with the attacker’s new segment.
By conducting transactions on the honest chain prior to the attack, and once the attacker’s conflicting transactions on the attacking chain are revealed, the honest transactions are subsequently nullified.
These large scale attacks are typically performed against cryptocurrency exchanges. By depositing coins into an exchange the attacker can trade at-risk Ethereum Classic for Bitcoin or another valuable cryptocurrency. Then, the attacker can revert these transactions to regain the Ethereum Classic.
The attacker can continue to plunder in this fashion so long as they maintain control over 50 percent of the network’s mining capability. To learn more about 51 percent attacks read CryptoSlate’s deep-dive.
The reorganizations emphasize the vulnerability of smaller proof-of-work cryptocurrencies. It is unknown how long Ethereum Classic will endure this attack, but, for the time being, it is recommended that holders halt any transactions with the cryptocurrency to prevent their transactions from being reverted.
Ethereum Classic Market Data
At the time of press 6:21 pm UTC on Jan. 7, 2019, Ethereum Classic is ranked #18 by market cap and the price is down 7.77% over the past 24 hours. Ethereum Classic has a market capitalization of $531.42 million with a 24-hour trading volume of $150.01 million. Learn more about Ethereum Classic ›
Crypto Market Summary
At the time of press 6:21 pm UTC on Jan. 7, 2019, the total crypto market is valued at at $135.61 billion with a 24-hour volume of $15.85 billion. Bitcoin dominance is currently at 51.87%. Learn more about the crypto market ›
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Posted In: Hacks, Price Watch
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In this article
Ethereum Classic
$27.6911
Ethereum Classic (ETC) is a continuation of the original Ethereum blockchain – the classic version preserving untampered history prior to the July 2016 DAO hack..
Coinbase
Coinbase is a digital currency exchange and wallet service that allows individuals to buy, sell, and store digital currencies, such as Bitcoin, Ethereum, and Litecoin.
Poloniex
Poloniex is a US-based cryptocurrency exchange platform offering a wide variety of digital assets.
Kraken
Kraken is a San Francisco-based digital asset exchange in euro volume and liquidity that trades various currencies, including Canadian dollars, US dollars, British pounds, and Japanese yen.
