Ethereum Classic

Ethereum Classic is an open source, blockchain-based distributed computing platform featuring smart contract (scripting) functionality.[1] It supports a modified version of Nakamoto consensus via transaction-based state transitions executed on a public Ethereum Virtual Machine (EVM).

Ethereum Classic
Ethereum Classic
Original author(s)Vitalik Buterin, Gavin Wood
Developer(s)Open-source software development
Initial release30 July 2015 (2015-07-30)
Stable releaseThanos / 28 November 2020 (2020-11-28)
Development statusActive
Project goal(s)Censorship resistant network executing contracts exactly as programmed
Software usedEVM 61 bytecode
Written inC++, Go, Python, Rust, Scala
Operating systemCross-platform
Platformx86-64, ARM
Size592,734,752 KB
Available inGlobal
TypeOpen Source Software
LicenseOpen-source licenses
As ofNov 2020
Average performance63,776,740 Transactions
Active users8,185 Addresses
Total users1,745,907 Addresses
Active hosts779 Nodes
Total hosts779 Nodes
Websiteethereumclassic.org

Ethereum Classic maintains the original, unaltered history of the Ethereum network.[2] 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.[2] The Ethereum Foundation applied their trademark to the new, altered version of the Ethereum blockchain; Ethereum (ticker: ETH).[2] The older, unaltered version of Ethereum was renamed and continued on as Ethereum Classic (ticker: ETC).[2]

Ethereum Classic's native Ether token is a cryptocurrency traded on digital currency exchanges under the ticker symbol ETC.[3] 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 ETC 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 (EVM), 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.[4]

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 followed 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
2020-11-28 11,700,000 Thanos

The DAO bailout
Main article: The DAO (organization)

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,[5] the Ethereum network split into two separate blockchains – the altered history was named Ethereum (ETH) and the unaltered history was named Ethereum Classic (ETC).[2]

  • The new chain with the altered history was branded as Ethereum (ticker: ETH) 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.[6]
  • 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 (ticker: ETC) with the BIP-44 Coin Index 61 and EVM Chain ID 61.[2]

Security vulnerabilities disclosed

On 28 May 2016, a paper was released detailing security vulnerabilities with the DAO that could allow Ether to be stolen.[7] On 9 June 2016, Peter Vessenes publicly disclosed the existence of a critical security vulnerability overlooked in many Solidity contracts, a recursive call bug. On 12 June 2016, Stephan Tual publicly claimed that the DAO funds were safe despite the newly-discovered critical security flaw.

Carbon vote

On 15 July 2016, a short notice on-chain vote was held on the DAO hard fork.[8] 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 (87%) voted in favor, 1/4 of which came from a single address, and 577,899 ETH (13%) opposed the DAO fork.[8] The expedited process of the carbon vote drew criticism from opponents of the DAO fork. While proponents of the fork were quick to market the vote as an effective consensus mechanism and pushed forward with the DAO fork four days later.[9]

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.[8][10]

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 merits 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.

Protocol parity

In an attempt to modernize the Ethereum Classic protocol, several protocol upgrades where scheduled to activate features that the Ethereum network already enabled over the past years. Atlantis, activated in September 2019, enabled the outstanding Byzantium changes, Agharta, in January 2020, brought Ethereum's Constantinople patches, and Phoenix finally achieved protocol parity between Ethereum Classic and Ethereum with the introduction of the Istanbul protocol upgrade. Since the Phoenix protocol activated, applications are fully cross-compatible between the both networks.

Mining algorithm

After a series of 51% attacks on the Ethereum Classic network in 2020,[11] a change to the underlaying Ethash mining algorithm was considered by the community to prevent being a minority proof-of-work chain in the Ethash mining algorithm where Ethereum is dominating the hashrate. After evaluating various options such as Monero's RandomX or the standardized SHA-3-256, it was eventually decided to double the Ethash epoch duration from 30,000 to 60,000 in order to reduce the DAG size and prevent Ethash miners to easily switch to Ethereum Classic. This modified Ethash is also referred to as EtcHash or Thanos upgrade.

Characteristics
Further information: Cryptocurrency
Ether (ETC)
ETC logo
Denominations
PluralEther(s)
SymbolΞ
Ticker symbolETC
NicknameEther Classic, Eth Classic, Classic
Previous namesEthereum, ETH, Eth
Precision18
Subunits
 10−9Gwei
 10−18Wei
Development
Original author(s)Vitalik Buterin, Gavin Wood
White paperethereum whitepaper
Implementation(s)EVM 61
Initial releaseFrontier / 30 July 2015 (2015-07-30)
Latest releaseThanos / 28 November 2020 (2020-11-28)
Code repositorygithub.com/ethereumclassic
Development statusActive
Written inC++, Go, Python, Rust, Scala
Operating systemCross-platform
Developer(s)Open-source software development
Source modelOpen-source model
LicenseOpen-source licenses
Websiteethereumclassic.org
Ledger
Ledger start30 July 2015 (2015-07-30)
Split height#1,920,000 / 20 July 2016 (2016-07-20)
Split fromEthereum (ETH)
Split ratio1:1
Timestamping schemeProof-of-Work - Etchash
Hash functionKeccack
Issuance scheduleBlock reward reduction of 20% every 5,000,000 blocks
Block reward3.2 ETC
Block time13 secs
Block explorerBlockScout, Expedition
Circulating supply116,320,000
Supply limit210,700,000
Valuation
Exchange rate$6.40 (Nov 2020)
Market cap$742 million (Nov 2020)

    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.[12][13] 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.[14] Unlike Bitcoin, Ethereum Classic operates using accounts and balances in a manner called state transitions. This does not rely upon unspent transaction outputs (UTXOs). 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, the Keccak-256 hash of the public key of that account is needed. 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 (Ξ) is generally used for its currency symbol. It is also used to pay for transaction fees and computational services on the Ethereum Classic network.[15]

    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 (big endian) of the ECDSA public key (the curve used is the so-called secp256k1, the same as bitcoin). In hexadecimal, two 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.[16] 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 (ECIP) 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

    Code is law

    The people who continued with Ethereum Classic advocate for blockchain immutability, and the concept that "code is law" [17] against the pro-fork side (Ethereum) which largely argued for extra-protocol intentionality, decentralized decision-making, and conflict resolution.[18]

    Attacks

    TheDAO fork replay attacks

    On 20 July 2016, due to reliance on the same clients, the DAO fork created a replay attack where a transaction was broadcast on both the ETC and ETH networks. On 13 January 2017, the Ethereum Classic network was updated to resolve transaction replay attacks. The networks are now officially operating separately.[8]

    RHG sells stolen ETC

    On 10 August 2016, the ETH proponent Robin Hood Group transferred 2.9 million stolen ETC to Poloniex in an attempt to sell ETC for ETH on the advice of Bitly SA; 14% was successfully converted to ETH and other currencies, 86% was frozen by Poloniex.[8] On 30 August 2016, Poloniex returned the ETC funds to the RHG. They set up a refund contract on the ETC network.

    Classic Ether Wallet website attack

    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.[19]

    51% double spend attacks

    In January 2019, Ethereum Classic was subject to double-spending attacks.[20][21] From July through August 2020, Ethereum Classic suffered from more 51% attacks.[22][23]

    References
    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. Vigna, Paul (1 August 2016). "The Great Digital-Currency Debate: 'New' Ethereum Vs. Ethereum 'Classic'". The Wall Street Journal (Blog). News Corp. Retrieved 5 March 2020.
    3. Russel, Jon (11 June 2018). "Coinbase will add Ethereum Classic to its exchange 'in the coming months'". TechCrunch.com. TechCrunch. Retrieved 5 March 2020.
    4. Tapscott, Don (2016). Blockchain revolution : how the technology behind bitcoin is changing money, business, and the world. Toronto, Ontario, Canada: Portfolio/Penguin. ISBN 978-0670069972.
    5. Waters, Richard (18 June 2016). "'Ether' brought to earth by theft of $50m in cryptocurrency". Financial Times. Retrieved 19 October 2018.
    6. Leising, Matthew (13 June 2017). "Ether thief remains mystery year after $55 million heist". www.bloomberg.com. Bloomberg News.
    7. 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.
    8. 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
    9. De Jesus, Cecille (19 July 2016). "The DAO Heist Undone: 97% of ETH Holders Vote for the Hard Fork". Futurism, LLC. Archived from the original on 7 August 2017. Retrieved 16 May 2017.
    10. Matthew Leising (2017-06-13): "The Ether Thief". Online article, Bloomberg. Accessed on 2019-02-16.
    11. "Ethereum Classic faced '51 percent attack'" (in Turkish). Bloomberg HT. 31 August 2020.
    12. "Blockchains: The great chain of being sure about things". The Economist. 31 October 2015. Retrieved 18 June 2016. The technology behind bitcoin lets people who do not know or trust each other build a dependable ledger. This has implications far beyond the crypto currency.
    13. Narayanan, Arvind; Bonneau, Joseph; Felten, Edward; Miller, Andrew; Goldfeder, Steven (2016). Bitcoin and Cryptocurrency Technologies: a Comprehensive Introduction. Princeton: Princeton University Press. ISBN 978-0-691-17169-2.
    14. Iansiti, Marco; Lakhani, Karim R. (January 2017). "The Truth About Blockchain". Harvard Business Review. Harvard University. Retrieved 17 January 2017. The technology at the heart of bitcoin and other virtual currencies, blockchain is an open, distributed ledger that can record transactions between two parties efficiently and in a verifiable and permanent way.
    15. Popper, Nathaniel (27 March 2016). "Ethereum, a Virtual Currency, Enables Transactions That Rival Bitcoin's". New York Times. Archived from the original on 24 July 2016. Retrieved 2 September 2016.
    16. Wood, Gavin (3 February 2018). "ETHEREUM: A SECURE DECENTRALISED GENERALISED TRANSACTION LEDGER (EIP-150)". yellowpaper.io. Archived from the original on 3 February 2018. Retrieved 3 February 2018.
    17. Pearson, Jordan (27 July 2016). "The Ethereum Hard Fork Spawned a Shaky Rebellion". Motherboard. Retrieved 15 May 2017.
    18. Primavera De Filippi (11 July 2016). "A $50M Hack Tests the Values of Communities Run by Code". Motherboard. Retrieved 15 May 2017.
    19. Russon, Mary-Ann (30 June 2017). "Classic Ether Wallet has been hacked – do not use it to send currency". International Business Times.
    20. Kharif, Olga (7 January 2019). "Ethereum Classic Movements Halted by Coinbase on Signs of Attack". Bloomberg.
    21. Goodin, Dan (7 January 2019). "Almost $500,000 in Ethereum Classic coin stolen by forking its blockchain". Ars Technica.
    22. Berbedj, Loana (17 August 2020). "Ethereum Classic cryptocurrency victim of two computer attacks in one week". Les Echos (in French).
    23. "Ethereum Classic faced '51 percent attack'" (in Turkish). Bloomberg HT. 31 August 2020.
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