|Initial release||July 30, 2015|
|Written in||C++, Go, Rust, Scala|
|Operating system||Clients available for Linux, Windows, macOS, POSIX|
|License||Multiple open-source licenses|
|Block reward||4 ETC|
Ethereum Classic is an open-source, public, blockchain-based distributed computing platform featuring smart contract (scripting) functionality. 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.
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. In the same month a paper was released detailing security vulnerabilities with The DAO that could allow ether to be stolen. 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.
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.
The people who continued with Ethereum Classic advocate for blockchain immutability, and the concept that "code is law"  against the pro-fork side (Ethereum) which largely argued for extra-protocol intentionality, decentralized decision-making, and conflict resolution. 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.
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