Ethereum Classic

Verified Timeline

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. The first Ethereum Classic block that was not included in the forked Ethereum chain was block number 1,920,000, generated on 20 July 2016. A carbon vote on 15 July 2016 saw 87% of votes in favor of the fork, with 5.5% of the total ether supply participating (not 5.5% of voters). Ethereum Classic permanently defused the Difficulty Bomb at block 5,900,000, committing the network to proof-of-work. After a series of 51% attacks in 2020, the mining algorithm was modified to ETChash by doubling the Ethash epoch duration from 30,000 to 60,000 blocks. Through the Phoenix upgrade, Ethereum Classic achieved parity with Ethereum's Istanbul protocol, but not full protocol parity with all subsequent Ethereum upgrades.

In Their Own Story

The narrative of Ethereum Classic is defined by a single moment on July 20, 2016, when the network split. While the majority voted to reverse a hack through an irregular state change, a minority held firm to the principle that the ledger must remain unaltered. These participants continued mining block 1,920,000, the first block exclusive to the new chain. Over the years, this commitment led to specific technical evolutions, such as defusing the 'Difficulty Bomb' at block 5,900,000 to stay on proof-of-work and adopting the ETChash algorithm in 2020 to secure against 51% attacks. Today, the chain stands as a direct continuation of the original Ethereum codebase from 2015.

Reader's Guide

ETC is a fundamental token for operation of Ethereum Classic, providing a public distributed ledger for transactions. It is used to pay for Gas, a unit of computation used in transactions and other state transitions. It is listed under the currency code ETC and traded on cryptocurrency exchanges, and the Greek uppercase Xi character (Ξ) is generally used for its currency symbol. Ether is created as a reward to network nodes for mining, which validates computations on the EVM. 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 public and private keys or addresses, which can be generated through BIP 39 style mnemonics for a BIP 32 HD wallet, though this is unnecessary as Ethereum Classic does not operate in a UTXO scheme.

Did You Know?

• Ethereum Classic maintains the original, unaltered Ethereum blockchain history after the DAO hack.
• The first Ethereum Classic block not in the forked chain was block 1,920,000 on 20 July 2016.
• Ethereum Classic permanently defused the Difficulty Bomb at block 5,900,000 to stay proof-of-work.
• In 2020, ETC modified its mining algorithm to ETChash by doubling the epoch duration from 30,000 to 60,000 blocks.
• By 2025, the network's ETChash hashrate surpassed 300 terahashes per second (TH/s).