Ethereum Classic

The original Ethereum blockchain, preserving immutability through proof-of-work.

Ethereum Classic is a blockchain-based distributed computing platform that offers smart contract (scripting) functionality. It is open source and supports a modified version of Nakamoto consensus via transaction-based state transitions executed on a public Ethereum Virtual Machine (EVM). It is now the largest smart contract platform secured by a proof-of-work consensus mechanism, following Ethereum's transition to proof-of-stake in 2022.

Quick Facts

Author

Vitalik Buterin, Gavin Wood

Developer

Open-source software development

Released

30 July 2015

Latest release version

Spiral

Latest release date

4 February 2024

Software

EVM 61 bytecode

Funding

Open Source Software

Programming language

C++
Go
Python
Rust
Scala

Lore & Background

Ethereum Classic maintains the original, unaltered history of the Ethereum network. The Ethereum project's mainnet was initially released via Frontier on 30 July 2015. Due to a hack of a third-party project, The DAO, the Ethereum Foundation created a new version of the Ethereum mainnet on 20 July 2016 with an irregular state change that erased the DAO theft from the Ethereum blockchain history. The older, unaltered version of Ethereum was renamed and continued on as Ethereum Classic. On 20 July 2016, as a result of the exploitation of a flaw in The DAO project's smart contract software and subsequent theft of $50 million worth of Ether, the Ethereum network split into two separate blockchains – the altered history was named Ethereum (ETH) and the unaltered history was named Ethereum Classic (ETC). The new chain with the altered history was branded as Ethereum (code: ETH) with the BIP-44 Coin Index 60 and EVM Chain ID 1. The non-fork chain continued as Ethereum Classic (code: ETC) with the BIP-44 Coin Index 61 and EVM Chain ID 61. On 15 July 2016, a short notice on-chain vote was held on the DAO hard fork. Of the 82,054,716 ETH in existence, only 4,542,416 voted, for a total voter turnout of 5.5% of the total supply on 16 July 2016; 3,964,516 ETH (87%) voted in favor, and 577,899 ETH (13%) opposed the DAO fork. The first Ethereum Classic block not included in the forked Ethereum chain was block number 1,920,000, generated on 20 July 2016.

Reader's Guide

Ethereum Classic's native Ether token is a cryptocurrency traded on digital currency exchanges under the currency code ETC. Ether is created as a reward to network nodes for mining, which validates computations performed on Ethereum Classic's EVM. ETC is used to pay for Gas, a unit of computation used in transactions and other state transitions. The Greek uppercase Xi character (Ξ) is generally used for its currency symbol. To send Ether to an account, the Keccak-256 hash of the public key of that account is needed. Ether accounts are pseudonymous. A cryptocurrency wallet stores the public and private keys or addresses which can be used to receive or spend Ether. These can be generated through BIP 39 style mnemonics for a BIP 32 'HD wallet', though in the Ethereum tech stack this is unnecessary as it does not operate in a UTXO scheme.

Did You Know?

The Phoenix upgrade achieved protocol parity with Ethereum's Istanbul protocol, not full parity with all subsequent upgrades.
Ethereum Classic permanently defused the Difficulty Bomb, committing to proof-of-work.
The ETChash mining algorithm doubled the Ethash epoch duration to reduce DAG size and prevent easy switching from Ethereum miners.