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Ethereum logo 2014.svg
The Ethereum Project's logo, first used in 2014.
Initial release 30 July 2015
Development status Active
Written in C++, Go, Rust
Operating system Clients available for Linux, Windows, macOS, POSIX, Raspbian
Platform x86, ARM
Type Decentralized computing
License Multiple open-source licenses

Ethereum is an open-source, public, blockchain-based distributed computing platform featuring smart contract (scripting) functionality.[1][irrelevant citation][2][not in citation given] 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 also provides a cryptocurrency token called "ether", which can be transferred between participants and is used to compensate participant nodes for computations performed. 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.[3][non-primary source needed][4][non-primary source needed][5][unreliable source?][6][unreliable source?]

Ethereum was initially proposed in late 2013 by Vitalik Buterin, a cryptocurrency researcher and programmer. Development was funded by an online crowdsale during July–August 2014.[7] The system went live on 30 July 2015. A hard fork on the network occurred on July 20, 2016, resulted in two separate blockchains: Ethereum and Ethereum Classic. Ethereum Classic is a separate blockchain that came into existence as the original unforked blockchain, consolidating members of the Ethereum community who rejected this fork on philosophical grounds.[8]



Ethereum was initially described in a white paper by Vitalik Buterin,[9] a programmer involved with Bitcoin, in late 2013 with a goal of building decentralized applications.[10][11] Buterin had argued that Bitcoin needed a scripting language for application development. Failing to gain agreement, he proposed development of a new platform with a more general scripting language.[12]:88

The Ethereum software project was initially developed in early 2014 by a Swiss company, Ethereum Switzerland GmbH (EthSuisse).[13][14][unreliable source?] Subsequently, a Swiss non-profit foundation, the Ethereum Foundation (Stiftung Ethereum) was set up as well.[7] Development was funded by an online public crowdsale during July–August 2014, with the participants buying the Ethereum value token (ether) with another digital currency, bitcoin.[7] While there was early praise for the technical innovations of Ethereum, questions were also raised about its security and scalability.[10]


Ethereum's live blockchain was launched on 30 July 2015.[15][not in citation given][16] The initial version of Ethereum—called "Frontier"—uses a proof of work consensus algorithm, although a later version is expected to replace that with a proof of stake algorithm.[12]:32

Ethereum versions[edit]

Since the initial version, the Ethereum network has accomplished several so-called hard forks, important changes because they are backwards-incompatible.

Version Code name Release date
Old version, no longer supported: 1 Frontier July 2014[citation needed]
Old version, no longer supported: 1.1 Protocol Update 1 August 4, 2015 [17][non-primary source needed]
Old version, no longer supported: 2 Homestead February 29, 2016 [18][non-primary source needed]
Old version, no longer supported: 3 The DAO July 20, 2016 [19][non-primary source needed]
Current stable version: 4 Spurious Dragon November 18, 2016 [20][non-primary source needed]
Future release: ? Metropolis [21]  ?
Future release: ? Serenity [21]  ?
Old version
Older version, still supported
Latest version
Latest preview version
Future release
First hard fork

The first hard fork introduced a difficulty bomb[when?] to incentivize an upgrade to proof of stake when this system will be ready.[22]

Second hard fork—Homestead release

The second hard fork was made in Spring 2016[clarification needed] and marked the first stable release: Homestead.[citation needed]

Third hard fork—The DAO

In June 2016, The DAO, a platform for the autonomous governance of investment capital, was found to contain an unexpected code path which would allow any sophisticated user to withdraw an arbitrary amount of funds from the DAO. This was exploited by an unknown party on the 16th of June, who managed to move about one third of the Ether held then by the DAO (at the time valued at 50 million USD) into a clone of the DAO, a "ChildDAO" whose control was held by only this party.[23][24] As a consequence of the way the DAO was programmed, these moved funds would remain unavailable for withdrawal for about a month.[25]

The Ethereum community debated how and whether to reclaim the ether, and whether to shut down The DAO,[25] as the decentralised nature of The DAO and of Ethereum meant a lack of a central authority that could take quick action, instead requiring community consensus.[24] After a few weeks' discussion, on 20 July 2016 Ethereum hard-forked (a backward-incompatible change[26]) creating a new fork to reverse the hack and return The DAO funds, with the original chain adopting the name Ethereum Classic.[27] This was the first time any mainstream blockchain was forked to reverse a transaction in order to make reparations to investors in a failed enterprise.[26]

After The DAO fork, Ethereum subsequently forked multiple times to deal with other attacks.[28]

Fourth hard fork—de-bloating & DDoS protection

Towards the end of November 2016, a fourth hard fork took place. This hard fork successfully de-bloated the blockchain and attempted to prevent further spam attacks by hackers.[29]



Symbol Ξ or ETH
User(s) Worldwide
Currency type Cryptocurrency

The value token of the Ethereum blockchain is called ether. It is listed under the diminutive ETH and traded on cryptocurrency exchanges. It is also used to pay for transaction fees and computational services on the Ethereum network.[30]

Tokens can be volatile per circumstances, such as ether's plunge from $21.50 to $8 when The DAO was hacked on June 17, 2016.[24]

Smart contracts[edit]

Main article: Smart contract

Smart contracts are applications with a state stored in the blockchain. They can facilitate, verify, or enforce the negotiation or performance of a contract. Ethereum contracts can be implemented in various Turing complete scripting languages.[31][unreliable source?] The Ethereum system has been described by the New York Times as "a single shared computer that is run by the network of users and on which resources are parceled out and paid for by Ether."[30][32][irrelevant citation]

Contracts on the public blockchain[edit]

As the contracts can be public, it opens up the possibility to prove functionality, e.g. self-contained provably fair casinos.[33]

One issue related to using smart contracts on a public blockchain is that bugs, including security holes, are visible to all but cannot be fixed quickly.[34] One example of this is the 17 June 2016 attack on The DAO, which could not be quickly stopped or reversed.[23]

There is ongoing research on how to use formal verification to express and prove non-trivial properties. A Microsoft Research report noted that writing solid smart contracts can be extremely difficult in practice, using The DAO hack to illustrate this problem. The report discussed tools that Microsoft had developed for verifying contracts, and noted that a large-scale analysis of published contracts is likely to uncover widespread vulnerabilities. The report also stated that it is possible to verify the equivalence of a Solidity program and the EVM code.[35]

Ethereum Virtual Machine[edit]

The Ethereum Virtual Machine (EVM)[36][non-primary source needed] is the runtime environment for smart contracts in Ethereum. The opcodes available to the EVM are specified in the Ethereum Yellow Paper by Gavin Wood.[37][non-primary source needed] It is sandboxed and also completely isolated from the network, filesystem or other processes of the host computer system. Every Ethereum node in the network runs an EVM implementation and executes the same instructions. Ethereum Virtual Machines have been implemented in go, C++, Python, Ruby, and WebAssembly (currently under development).[citation needed]

Programming languages[edit]

Main article: Solidity

Smart contracts can be written in Solidity, Serpent[38] and Viper (derivatives of Python), and LLL.[39] The EVM also runs on Mutan (deprecated).[40][non-primary source needed] The smart contracts are subsequently compiled into the EVM bytecode and deployed to run on the Ethereum blockchain.[39][41]


The Ethereum Foundation funded reference implementations of the Ethereum client in several languages, including Python,[42][non-primary source needed] C++,[43][non-primary source needed] Go[43][non-primary source needed] and Java.[44][non-primary source needed][45][non-primary source needed][43][non-primary source needed] Implementations not funded by the foundation are available in Rust,[46][non-primary source needed][47] JavaScript[48][non-primary source needed][43][non-primary source needed] and Ruby.[49][non-primary source needed]


In Ethereum all smart contracts are stored publicly on every node of the blockchain, which has trade-offs.[50] The downside is that performance issues arise in that every node is calculating all the smart contracts in real time, resulting in slower speeds.[50] Ethereum engineers have been working on sharding the calculations, but no solution had been detailed by early 2016.[50] As of January 2016, the Ethereum protocol could process 25 transactions per second.[50] In September 2016, Buterin presented proposals to increase scalability.[51]


The Ethereum platform has multiple proposed uses. Bloomberg describes it as "shared software that can be used by all but is tamperproof."[52] Ethereum is used as a platform for decentralized applications, decentralized autonomous organizations and smart contracts, with "dozens of functioning applications built" on it by March 2016 according to the New York Times.[30][53] The intended scope of applications include projects related to finance, the internet-of-things, farm-to-table produce, electricity sourcing and pricing, and sports betting.[30] Decentralized autonomous organizations may enable a wide range of possible business models that were previously impossible or too costly to run.[54]


The New York Times noted in March 2016 that Ethereum adoption was still at an early stage and that Ethereum could encounter technical and legal problems that would slow its growth.[30] Some Bitcoin advocates say that Ethereum may "face more security problems than Bitcoin because of the greater complexity of the software." The article also said, "The system is complicated enough that even people who know it well have trouble describing it in plain English".[30]

Microsoft announced a partnership with ConsenSys, a blockchain startup focused on Ethereum technology. Customers of popular cloud-based business service Microsoft Azure have access to third-party tools that "allow them to experience and build with cloud-based blockchain applications, from securities trading to cross-border payments".[2][not in citation given]


This list is not exhaustive and some elements can be outdated.

Enterprise software[edit]

Ethereum is being tested by enterprise software companies for various applications. Interested parties include Microsoft, IBM, JPMorgan Chase,[30][76] Deloitte,[77] R3,[53] Innovate UK (cross-border payments prototype)[78][79][unreliable source?]


Permissioned ledgers[edit]

Ethereum is used and being investigated as a permissioned blockchain in various projects.

  • J.P. Morgan Chase is developing a blockchain, atop Ethereum. The system, dubbed "Quorum," is designed to toe the line between private and public in the realm of shuffling derivatives and payments. The idea is to satisfy regulators who need seamless access to financial goings-on, while protecting the privacy of parties that don’t wish to reveal their identities nor the details of their transactions to the general public.[82]
  • Royal Bank of Scotland has announced that it has built a Clearing and Settlement Mechanism (CSM) based on the Ethereum distributed ledger and smart contract platform. According to a technical paper, "The test results evidenced a throughput of 100 payments per second, with 6 simulated banks, and a single trip mean time of 3 seconds and maximum time of 8 seconds. This is the level appropriate for a national level domestic payments system".[83][third-party source needed]


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External links[edit]