Ethereum Classic

Ethereum Classic is an open-source, public, blockchain-based distributed computing platform featuring smart contract (scripting) functionality.[1] It provides a decentralized Turing-complete virtual machine, the Ethereum Virtual Machine (EVM), which can execute scripts using an international network of public nodes. Ethereum Classic and Ethereum have a value token called "ether", which can be transferred between participants, stored in a cryptocurrency wallet and is used to compensate participant nodes for computations performed in the Ethereum Platform. The classic ether token is traded on cryptocurrency exchanges under the ticker symbol ETC. Gas, an internal transaction pricing mechanism, is used to prevent spam on the network and allocate resources proportionally to the incentive offered by the request.

Ethereum Classic
Ticker symbolETC
Initial releaseJuly 30, 2015 (2015-07-30)
Code repository
Development statusActive
Project fork ofEthereum
Written inC++, Go, Rust, Scala
Operating systemClients available for Linux, Windows, macOS, POSIX
LicenseMultiple open-source licenses
Timestamping schemeProof-of-work
Hash functionEthash
Block reward4 ETC


In May 2016, a venture capital fund called The DAO built on Ethereum raised around $168 million, with the intention of investing in projects using smart contracts.[2] In the same month a paper was released detailing security vulnerabilities with The DAO that could allow ether to be stolen.[3] In June, 3.6 million Ether (approximately $50 million USD) was taken from accounts in The DAO and moved to another account without the owners' consent, exploiting one of the vulnerabilities that had been raised in May. Members of The DAO and the Ethereum community debated what actions, if any, should occur to resolve the situation. A vote occurred and in July 2016 it was decided to implement a hard fork in the Ethereum code and to move the Ether taken in the exploit to a new smart contract through which it would be restored to the owners from whom it had been taken.

Ethereum Classic came into existence when some members of the Ethereum community rejected the hard fork on the grounds of "immutability", the principle that the blockchain cannot be changed, and decided to keep using the unforked version of Ethereum. The first Ethereum Classic block that was not included in the forked Ethereum chain was block number 1,920,000, which was generated by Classic miners on July 20, 2016.[4][5]

Ethereum Classic underwent a technical hard fork to adjust the internal pricing for running various op codes on the Ethereum Virtual Machine (EVM) on 25 October 2016, similar to the hard fork the ETH chain did a week earlier. The goal was to more rationally price various compute-intensive and external reference commands to reduce the incentive for spammers who had conducted a month-long distributed denial-of-service attack on the Ethereum Classic network. A hard fork that occurred early 2017 successfully delayed the so-called "difficulty bomb", originally added to Ethereum's code in September 2015 in order to exponentially increase the difficulty of mining, or the competitive process by which new transaction blocks are added to the network.[6]

The people who continued with Ethereum Classic advocate for blockchain immutability, and the concept that "code is law" [7] against the pro-fork side (Ethereum) which largely argued for extra-protocol intentionality, decentralized decision-making, and conflict resolution.[8][9] The project, however, is not officially supported by the Ethereum Foundation.

On 29 June 2017, the Ethereum Classic Twitter account made a public statement indicating reason to believe that the website for Classic Ether Wallet had been compromised. The Ethereum Classic Twitter account confirmed the details released via Threatpost. The Ethereum Classic team worked with Cloudflare to place a warning on the compromised domain warning users of the phishing attack.[10]

In January 2019, Ethereum Classic was subject to double-spending attacks.[11][12]


  1. Vigna, Paul (28 October 2015). "BitBeat: Microsoft to Offer Ethereum-Based Services on Azure". The Wall Street Journal (Blog). News Corp. Retrieved 17 February 2016.
  2. "The Biggest Crowdfunding Project Ever Was Supposed to Create Manager-free Companies. But It's a Mess". WIRED. Retrieved 12 July 2017.
  3. Popper, Nathaniel (27 May 2016). "Paper Points Up Flaws in Venture Fund Based on Virtual Money". The New York Times. ISSN 0362-4331. Retrieved 12 July 2017.
  4. Andreas M. Antonopoulos, Gavin Wood (2018): "Ethereum timeline" . In Mastering Ethereum: Building Smart Contracts and DApps, page 329. O'Reilly Media; 424 pages. ISBN 9781491971918
  5. Matthew Leising (2017-06-13): "The Ether Thief". Online article, Bloomberg. Accessed on 2019-02-16.
  6. Vigna, Paul (1 August 2016). "The Great Digital-Currency Debate: 'New' Ethereum Vs. Ethereum 'Classic'". Down Jones & Company Inc. Retrieved 15 May 2017.
  7. Pearson, Jordan (27 July 2016). "The Ethereum Hard Fork Spawned a Shaky Rebellion". Motherboard. Retrieved 15 May 2017.
  8. Ethereum info (4 June 2011). "Ethereum (ETH) kopen, verkopen en koersen". (in Dutch). Retrieved 8 March 2018.
  9. Primavera De Filippi (11 July 2016). "A $50M Hack Tests the Values of Communities Run by Code". Motherboard. Retrieved 15 May 2017.
  10. Russon, Mary-Ann (30 June 2017). "Classic Ether Wallet has been hacked – do not use it to send currency". International Business Times.
  11. Kharif, Olga (7 January 2019). "Ethereum Classic Movements Halted by Coinbase on Signs of Attack". Bloomberg.
  12. Goodin, Dan (7 January 2019). "Almost $500,000 in Ethereum Classic coin stolen by forking its blockchain". Ars Technica.
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