Ethereum Classic
Ethereum Classic is an open source, blockchain-based distributed computing platform featuring smart contract functionality. It supports a modified version of Nakamoto consensus via transaction-based state transitions executed on a public Ethereum Virtual Machine.
Ethereum Classic maintains the original, unaltered history of the Ethereum network. The Ethereum project's mainnet initially released via Frontier on 30 July 2015. However, due to a hack of a third-party project, the Ethereum Foundation created a new version of the Ethereum mainnet on 20 July 2016 with an irregular state change implemented that erased The DAO theft from the Ethereum blockchain history. The Ethereum Foundation applied their trademark to the new, altered version of the Ethereum blockchain; Ethereum. The older, unaltered version of Ethereum was renamed and continued on as Ethereum Classic.
Ethereum Classic's native Ether token is a cryptocurrency traded on digital currency exchanges under the ticker symbol ETC. Ether is created as a reward to network nodes for a process known as mining, which validates computations performed on Ethereum Classic's EVM. Implemented on 11 December 2017, the current Ethereum Classic monetary policy seeks the same goals as Bitcoin of being mechanical, algorithmic, and capped. ETC can be exchanged for network transaction fees or other assets, commodities, currencies, products, and services.
Ethereum Classic provides a decentralized Turing-complete virtual machine, the Ethereum Virtual Machine, which can execute scripts using an international network of public nodes. The virtual machine's instruction set is Turing-complete in contrast to others like Bitcoin Script. Gas, an internal transaction pricing mechanism, is used to mitigate spam and allocate resources on the network.
Milestones
Frontier
Several codenamed prototypes of the Ethereum platform were developed by the Ethereum Foundation, as part of their Proof-of-Concept series, prior to the official launch of the Frontier network. Ethereum classic would later follow this codebase after the DAO incident.| Date | Block | Milestone Name |
| 2015-07-30 | 0 | Frontier |
| 2015-09-08 | 200,000 | Ice Age |
| 2016-03-15 | 1,150,000 | Homestead |
| 2016-07-20 | 1,920,000 | The DAO Bailout |
| 2016-10-24 | 2,500,000 | Gas Reprice |
| 2017-01-13 | 3,000,000 | Die Hard |
| 2017-12-11 | 5,000,000 | Gotham |
| 2017-12-11 | 5,000,001 | 5M20 Era 2 |
| 2018-05-29 | 5,900,000 | Defuse Difficulty Bomb |
| 2019-09-12 | 8,772,000 | Atlantis |
| 2020-01-11 | 9,573,000 | Agharta |
| 2020-03-17 | 10,000,001 | 5M20 Era 3 |
| 2020-06-01 | 10,500,839 | Phoenix |
The DAO Bailout
In 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 and the unaltered history was named Ethereum Classic.- The new chain with the altered history was branded as Ethereum with the BIP-44 Coin Index 60 and EVM Chain ID 1 attributed to it by the trademark owning Ethereum Foundation. On this new chain, the history of the theft was erased from the Ethereum blockchain history.
- Some members of the Ethereum community ignored the attempt to rewrite history and continued to participate on the original Ethereum network. The non-fork chain with an unaltered history continued on as Ethereum Classic with the BIP-44 Coin Index 61 and EVM Chain ID 61.
Security Vulnerabilities Disclosed
The Carbon Vote
On 15 July 2016, a short notice on-chain vote was held on TheDAO hard fork. Of the 82,054,716 ETH in existence, only 4,542,416 voted for a total voter turn out of 5.5% of the total supply on 16 July 2016; 3,964,516 ETH voted in favor, 1/4 of which came from a single address, and 577,899 ETH opposed TheDAO fork. The expedited process of the Carbon Vote drew criticism from opponents of the TheDAO fork. While proponents of the fork were quick to market the vote as an effective consensus mechanism and pushed forward with TheDAO fork four days later.Block 1,920,000
The first Ethereum Classic block that was not included in the forked Ethereum chain was block number 1,920,000, which was generated by Ethereum Classic miners on 20 July 2016.Defuse Difficulty Bomb
A mechanism called the Difficulty Bomb was designed to push the Ethereum chain from Proof-of-Work consensus mechanism to Proof-of-Stake in the future by exponentially increasing the difficulty of mining. This Difficulty Bomb was added to the network on block 200,000 in an upgrade named Ice Age. While Ethereum Classic participants debated the merit of the Difficulty Bomb, a network upgrade called Die Hard at block 3,000,000 delayed the effects of the mechanism. Once the network participants came to consensus on the issue, Ethereum Classic upgraded its network on block 5,900,000 to permanently defuse the Difficulty Bomb. This abandoned a future with Proof-of-Stake and committed the network to the Proof-of-Work consensus mechanism.Characteristics
As with other cryptocurrencies, the validity of each ether is provided by a blockchain, which is a continuously growing list of records, called blocks, which are linked and secured using cryptography. By design, the blockchain is inherently resistant to modification of the data. It is an open, distributed ledger that records transactions between two parties efficiently and in a verifiable and permanent way. Unlike Bitcoin, Ethereum Classic operates using accounts and balances in a manner called state transitions. This does not rely upon unspent transaction outputs. The state denotes the current balances of all accounts and extra data. The state is not stored on the blockchain, it is stored in a separate Merkle Patricia tree. 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". In the Ethereum tech stack, this is unnecessary as it does not operate in a UTXO scheme. With the private key, it is possible to write in the blockchain, effectively making an ether transaction.To send ether to an account, you need the Keccak-256 hash of the public key of that account. Ether accounts are pseudonymous in that they are not linked to individual persons, but rather to one or more specific addresses.
Ether
Ether is a fundamental token for operation of Ethereum Classic, which thereby provides a public distributed ledger for transactions. It is used to pay for gas, a unit of computation used in transactions and other state transitions. Additionally, this currency is commonly referred to as Ethereum, Eth, Classic or ETC.It is listed under the ticker symbol ETC and traded on cryptocurrency exchanges, and the Greek uppercase Xi character is generally used for its currency symbol. It is also used to pay for transaction fees and computational services on the Ethereum Classic network.
Addresses
Ethereum Classic addresses are composed of the prefix "0x", a common identifier for hexadecimal, concatenated with the rightmost 20 bytes of the Keccak-256 hash of the ECDSA public key. In hexadecimal, 2 digits represent a byte, meaning addresses contain 40 hexadecimal digits. An example of an Ethereum Classic address is 0xb794f5ea0ba39494ce839613fffba74279579268. Contract addresses are in the same format, however, they are determined by sender and creation transaction nonce. User accounts are indistinguishable from contract accounts given only an address for each and no blockchain data. Any valid Keccak-256 hash put into the described format is valid, even if it does not correspond to an account with a private key or a contract. This is unlike Bitcoin, which uses base58check to ensure that addresses are properly typed.Monetary Policy
On 11 December 2017, the total supply of Ether on Ethereum Classic was hard capped at 210,700,000 ETC via the Gotham hard fork upgrade. This added a Bitcoin inspired deflationary emission schedule that is documented in Ethereum Classic Improvement Proposal 1017. The emission schedule, also known as 5M20, reduces the block reward by 20% every 5,000,000 blocks. Socially, this block reward reduction event has taken the moniker of "The Fifthening."| Date | 5M20 Era | Block | Block Reward | Total Era Emission |
| 2015-07-30 | Era 1 | 1 | 5 ETC | 25,000,000 ETC |
| 2017-12-11 | Era 2 | 5,000,001 | 4 ETC | 20,000,000 ETC |
| 2020-03-17 | Era 3 | 10,000,001 | 3.2 ETC | 16,000,000 ETC |
| 2022-04-15 | Era 4 | 15,000,001 | 2.56 ETC | 12,800,000 ETC |
| 2024-05-07 | Era 5 | 20,000,001 | 2.048 ETC | 10,240,000 ETC |