Ethereum is a decentralized blockchain with smart contract functionality. Ether (Abbreviation: ETH;[a] sign: Ξ) is the native cryptocurrency of the platform. Among cryptocurrencies, ether is second only to bitcoin in market capitalization.[2][3] It is open-source software.

Ethereum was conceived in 2013 by programmer Vitalik Buterin.[4] Additional founders of Ethereum included Gavin Wood, Charles Hoskinson, Anthony Di Iorio and Joseph Lubin.[5] In 2014, development work began and was crowdfunded, and the network went live on 30 July 2015.[6] Ethereum allows anyone to deploy permanent and immutable decentralized applications onto it, with which users can interact.[7] Decentralized finance (DeFi) applications provide financial instruments which do not directly rely on financial intermediaries like brokerages, exchanges, or banks. This facilitates borrowing against cryptocurrency holdings or lending them out for interest.[8][9] Ethereum also allows users to create and exchange non-fungible tokens (NFTs), which are tokens that can be tied to unique digital assets, such as images. Additionally, many other cryptocurrencies utilize the ERC-20 token standard on top of the Ethereum blockchain and have utilized the platform for initial coin offerings.

On 15 September 2022, Ethereum transitioned its consensus mechanism from proof-of-work (PoW) to proof-of-stake (PoS) in an upgrade process known as "the Merge". This has cut Ethereum's energy usage by 99%.[10]

History

Founding (2013–2014)

Ethereum co-founder Vitalik Buterin in 2015

Ethereum was initially described in late 2013 in a white paper by Vitalik Buterin,[4][11] a programmer and co-founder of Bitcoin Magazine, that described a way to build decentralized applications.[12][13] Buterin argued to the Bitcoin Core developers that Bitcoin and blockchain technology could benefit from other applications besides money and that it needed a more robust language for application development[14]: 88  that could lead to attaching[clarification needed] real-world assets, such as stocks and property, to the blockchain.[15] In 2013, Buterin briefly worked with eToro CEO Yoni Assia on the Colored Coins project and drafted its white paper outlining additional use cases for blockchain technology.[16] However, after failing to gain agreement on how the project should proceed, he proposed the development of a new platform with a more robust scripting language—a Turing-complete programming language[17]—that would eventually become Ethereum.[14]

Ethereum was announced at the North American Bitcoin Conference in Miami, in January 2014.[18] During the conference, Gavin Wood, Charles Hoskinson, and Anthony Di Iorio (who financed the project) rented a house in Miami with Buterin at which they could develop a fuller sense of what Ethereum might become.[18] Di Iorio invited friend Joseph Lubin, who invited reporter Morgen Peck, to bear witness.[18] Peck subsequently wrote about the experience in Wired.[19] Six months later the founders met again in Zug, Switzerland, where Buterin told the founders that the project would proceed as a non-profit. Hoskinson left the project at that time and soon after founded IOHK, a blockchain company responsible for Cardano.[18]

Ethereum has an unusually long list of founders.[20] Anthony Di Iorio wrote: "Ethereum was founded by Vitalik Buterin, Myself, Charles Hoskinson, Mihai Alisie & Amir Chetrit (the initial 5) in December 2013. Joseph Lubin, Gavin Wood, & Jeffrey Wilcke were added in early 2014 as founders." Buterin chose the name Ethereum after browsing a list of elements from science fiction on Wikipedia. He stated, "I immediately realized that I liked it better than all of the other alternatives that I had seen; I suppose it was that [it] sounded nice and it had the word 'ether', referring to the hypothetical invisible medium that permeates the universe and allows light to travel."[18] Buterin wanted his platform to be the underlying and imperceptible medium for the applications running on top of it.[21]

Development (2014)

Formal development of the software underlying Ethereum began in early 2014 through a Swiss company, Ethereum Switzerland GmbH (EthSuisse).[22] The idea of putting executable smart contracts in the blockchain needed to be specified before it could be implemented in software. This work was done by Gavin Wood, then the chief technology officer, in the Ethereum Yellow Paper that specified the Ethereum Virtual Machine.[23][24] Subsequently, a Swiss non-profit foundation, the Ethereum Foundation (Stiftung Ethereum), was founded. Development was funded by an online public crowd sale from July to August 2014, in which participants bought the Ethereum value token (ether) with another digital currency, bitcoin. While there was early praise for the technical innovations of Ethereum, questions were also raised about its security and scalability.[12]

Launch and the DAO event (2014–2016)

Several codenamed prototypes of Ethereum were developed over 18 months in 2014 and 2015 by the Ethereum Foundation as part of their proof-of-concept series.[4] "Olympic" was the last prototype and public beta pre-release. The Olympic network gave users a bug bounty of 25,000 ether for stress-testing the Ethereum blockchain. On 30 July 2015, "Frontier" marked the official launch of the Ethereum platform, and Ethereum created its "genesis block".[4][25] The genesis block contained 8,893 transactions allocating various amounts of ether to different addresses, and a block reward of 5 ETH.[citation needed]

Since the initial launch, Ethereum has undergone a number of planned protocol upgrades, which are important changes affecting the underlying functionality and/or incentive structures of the platform.[26][27] Protocol upgrades are accomplished by means of a hard fork.[citation needed]

In 2016, a decentralized autonomous organization called The DAO—a set of smart contracts developed on the platform—raised a record US$150 million in a crowd sale to fund the project.[28] The DAO was exploited in June 2016 when US$50 million of DAO tokens were stolen by an unknown hacker.[29][30] The event sparked a debate in the crypto-community about whether Ethereum should perform a contentious "hard fork" to reappropriate the affected funds.[31] The fork resulted in the network splitting into two blockchains: Ethereum with the theft reversed, and Ethereum Classic which continued on the original chain.[32]

Continued development and milestones (2017–present)

In March 2017, various blockchain startups, research groups, and Fortune 500 companies announced the creation of the Enterprise Ethereum Alliance (EEA) with 30 founding members.[33] By May 2017, the nonprofit organization had 116 enterprise members, including ConsenSys, CME Group, Cornell University's research group, Toyota Research Institute, Samsung SDS, Microsoft, Intel, J. P. Morgan, Cooley LLP, Merck KGaA, DTCC, Deloitte, Accenture, Banco Santander, BNY Mellon, ING, and National Bank of Canada.[34][35] By July 2017, there were over 150 members in the alliance, including MasterCard, Cisco Systems, Sberbank, and Scotiabank.[36]

By January 2018, ether was the second-largest cryptocurrency in terms of market capitalization, behind bitcoin.[37] As of 2021, it maintained that relative position.[2][3]

In 2019, Ethereum Foundation employee Virgil Griffith was arrested by the US government for presenting at a blockchain conference in North Korea.[38] He would later plead guilty to one count of conspiring to violate the International Emergency Economic Powers Act in 2021.[39]

In March 2021, Visa Inc. announced that it began settling stablecoin transactions using Ethereum.[40] In April 2021, JP Morgan Chase, UBS, and MasterCard announced that they were investing US$65 million into ConsenSys, a software development firm that builds Ethereum-related infrastructure.[41]

There were two network upgrades in 2021. The first was "Berlin", implemented on 14 April 2021.[42] The second was "London", which took effect on 5 August.[43] The London upgrade included Ethereum Improvement Proposal ("EIP") 1559, a mechanism for reducing transaction fee volatility. The mechanism causes a portion of the ether paid in transaction fees for each block to be destroyed rather than given to the block proposer, reducing the inflation rate of ether and potentially resulting in periods of deflation.[44]

On 27 August 2021, the blockchain experienced a brief fork that was the result of clients running different incompatible software versions.[45]

Ethereum 2.0

Ethereum enthusiasts gather for a Merge party in San Francisco in 2022.

Ethereum 2.0 (Eth2) was a set of three or more upgrades, also known as "phases", meant to transition the network's consensus mechanism to proof-of-stake, and to scale the network's transaction throughput with execution sharding and an improved EVM architecture.[46]

The switch from proof-of-work to proof-of-stake has cut Ethereum's energy usage by 99%. However, the impact this has on global energy consumption and climate change may be limited since the computers previously used for mining ether may be used to mine other cryptocurrencies that are energy-intensive.[10]

Design

Ether

Ether (ETH) is the cryptocurrency generated in accordance with the Ethereum protocol as a reward to validators in a proof-of-stake system for adding blocks to the blockchain. Ether is represented in the state as an unsigned integer associated with each account, this being the account's ETH balance denominated in wei (1018 wei = 1 ether).[47] At the end of each epoch, new ETH is generated by the addition of protocol-specified amounts to the balances of all validators for that epoch, with the block proposers receiving the largest portion. Additionally, ether is the only currency accepted by the protocol as payment for the transaction fee. The transaction fee is composed of two parts: the base fee and the tip. The base fee is "burned" (deleted from existence) and the tip goes to the block proposer. The validator reward together with the tips provide the incentive to validators to keep the blockchain growing (i.e. to keep processing new transactions). Therefore, ETH is fundamental to the operation of the network. Ether may be "sent" from one account to another via a transaction, which simply entails subtracting the amount to be sent from the sender's balance and adding the same amount to the recipient's balance.[48]

Ether is often erroneously referred to as "Ethereum".[49]

Accounts

There are two types of accounts on Ethereum: user accounts (also known as externally-owned accounts) and contracts. Both types have an ETH balance, may send ETH to any account, may call any public function of a contract or create a new contract, and are identified on the blockchain and in the state by an account address.[50]

Contracts are the only type of account that has associated code (a set of functions and variable declarations) and contract storage (the values of the variables at any given time). A contract function may take arguments and may have return values. In addition to control flow statements, the body of a function may include instructions to send ETH, read from and write to the contract's storage, create temporary storage (memory) that vanishes at the end of the function, perform arithmetic and hashing operations, call the contract's own functions or public functions of other contracts, create new contracts, and query information about the current transaction or the blockchain.[51]

Addresses

Ethereum 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 (the curve used is the so-called secp256k1). In hexadecimal, two digits represent a byte, and so addresses contain 40 hexadecimal digits after the "0x", e.g. 0xb794f5ea0ba39494ce839613fffba74279579268. Contract addresses are in the same format, however, they are determined by sender and creation transaction nonce.[24]

Virtual machine

The number of daily confirmed Ethereum transactions as of April 2021

The Ethereum Virtual Machine (EVM) is the runtime environment for transaction execution in Ethereum. It includes, among other things, a stack, memory, gas balance, program counter, and the state (including contract code). The EVM is stack-based, in that most instructions pop operands from the stack and push the result to the stack. The EVM is designed to be deterministic on a wide variety of hardware and operating systems, so that given a pre-transaction state and a transaction, each node produces the same post-transaction state, thereby enabling network consensus. The formal definition of the EVM is specified in the Ethereum Yellow Paper.[24][52] EVMs have been implemented in C++, C#, Go, Haskell, Java, JavaScript, Python, Ruby, Rust, Elixir, Erlang, and soon[when?] WebAssembly.[citation needed]

Gas

Gas is a unit of account within the EVM used in the calculation of the transaction fee, which is the amount of ETH a transaction's sender must pay to the network to have the transaction included in the blockchain. Each type of operation which may be performed by the EVM is hardcoded with a certain gas cost, which is intended to be roughly proportional to the monetary value of the resources (e.g. computation and storage) a node must expend or dedicate to perform that operation.[citation needed]

When a sender is creating a transaction, the sender must specify a gas limit and gas price. The gas limit is the maximum amount of gas the sender is willing to use in the transaction, and the gas price is the amount of ETH the sender wishes to pay to the network per unit of gas used. A transaction may only be included in the blockchain at a block slot that has a base gas price less than or equal to the transaction's gas price. The portion of the gas price that is in excess of the base gas price is known as the tip and goes to the block proposer; the higher the tip, the more incentive a block proposer has to include the transaction in their block, and thus the quicker the transaction will be included in the blockchain. The sender buys the full amount of gas (i.e. their ETH balance is debited the amount: gas limit × gas price) up-front, at the start of the execution of the transaction, and is refunded at the end for any unused gas. If at any point the transaction does not have enough gas to perform the next operation, the transaction is reverted but the sender is still only refunded for the unused gas. In user interfaces, gas prices are typically denominated in gigawei (Gwei), a subunit of ETH equal to 10−9 ETH.[53]

Applications

The EVM's instruction set is Turing-complete.[24] Popular uses of Ethereum have included the creation of fungible (ERC-20) and non-fungible (ERC-721) tokens with a variety of properties, crowdfunding (e.g. initial coin offerings), decentralized finance, decentralized exchanges, decentralized autonomous organizations (DAOs), games, prediction markets, and gambling.[citation needed]

Contract source code

Ethereum's smart contracts are written in high-level programming languages and then compiled down to EVM bytecode and deployed to the Ethereum blockchain. They can be written in Solidity (a language library with similarities to C and JavaScript), Serpent (similar to Python, but deprecated), Yul (an intermediate language that can compile to various different backends—EVM 1.0, EVM 1.5, and eWASM are planned), LLL (a low-level Lisp-like language), and Mutan (Go-based, but deprecated). There was also[when?] a research-oriented language under development called Vyper (a strongly-typed Python-derived decidable language).[citation needed] Source code and compiler information are usually published along with the launch of the contract so that users can see the code and verify that it compiles to the bytecode that is on-chain.[citation needed]

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.[54] One example of this is the 2016 attack on The DAO, which could not be quickly stopped or reversed.[29]

ERC-20 tokens

The ERC-20 (Ethereum Request-for-Comments #20) Token Standard allows for fungible tokens on the Ethereum blockchain. The standard, proposed by Fabian Vogelsteller in November 2015, implements an API for tokens within smart contracts. The standard provides functions that include the transfer of tokens from one account to another, getting the current token balance of an account, and getting the total supply of the token available on the network. Smart contracts that correctly implement ERC-20 processes are called ERC-20 Token Contracts, and they keep track of created tokens on Ethereum. Numerous cryptocurrencies have launched as ERC-20 tokens and have been distributed through initial coin offerings.[55]

Non-fungible tokens (NFTs)

Main article: Non-fungible token

Ethereum also allows for the creation of unique and indivisible tokens, called non-fungible tokens (NFTs).[56] Since tokens of this type are unique, they have been used to represent such things as collectibles, digital art, sports memorabilia, virtual real estate, and items within games.[57] The first NFT project, Etheria, a 3D map of tradable and customizable hexagonal tiles, was deployed to the network in October 2015 and demonstrated live at DEVCON1 in November of that year.[58] In 2021, Christie's sold a digital image with an NFT by Beeple for US$69.3 million, making him the third-most-valuable living artist in terms of auction prices at the time, although observers have noted that both the buyer and seller had a vested interest in driving demand for the artist's work.[59][60]

Decentralized finance

The web interface to Compound Finance's decentralized application where users can lend and borrow cryptocurrencies for interest

Main article: Decentralized finance

Decentralized finance (DeFi) offers traditional financial instruments in a decentralized architecture, outside of companies' and governments' control, such as money market funds which let users earn interest.[61] DeFi applications are typically accessed through a Web3-enabled browser extension or application, such as MetaMask, which allows users to directly interact with the Ethereum blockchain through a website.[62] Many of these DApps can connect and work together to create complex financial services.[63]

Examples of DeFi platforms include MakerDAO and Compound.[64] Uniswap, a decentralized exchange for tokens on Ethereum grew from US$20 million in liquidity to US$2.9 billion in 2020.[65] As of October 2020, over US$11 billion was invested in various DeFi protocols.[66] Additionally, through a process called "wrapping", certain DeFi protocols allow synthetic versions of various assets (such as bitcoin, gold, and oil) to be tradeable on Ethereum and also compatible with all of Ethereum's major wallets and applications.[66]

Enterprise software

Ethereum-based software and networks, independent from the public Ethereum chain, are being tested by enterprise software companies.[67] Interested parties include Microsoft, IBM, JPMorgan Chase,[48] Deloitte, R3, and Innovate UK (cross-border payments prototype).[68] Barclays, UBS, Credit Suisse, Amazon, Visa, and other companies are also experimenting with Ethereum.[69][70]

Permissioned ledgers

Ethereum-based permissioned blockchain variants are used and being investigated for various projects:

In 2017, JPMorgan Chase proposed developing JPM Coin on a permissioned-variant of Ethereum blockchain dubbed "Quorum".[71] It 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."[72]

Performance

As of January 2016, the Ethereum protocol could process about 25 transactions per second; this did not change after the move to proof-of-stake. In comparison, the Visa payment platform processes 45,000 payments per second. This has led some to question the scalability of Ethereum.[73]

A proposal to partition global state and computation into shard chains was presented at Ethereum's Devcon 3 in November 2017.[74] If implemented, each node in the network would only have to store and validate a subset of the network.

Ethereum's blockchain uses a Merkle-Patricia Trie to store account state in each block.[75] The trie allows for storage savings, set membership proofs (called "Merkle proofs"), and light client synchronization. The network has faced congestion problems, such as in 2017 in relation to CryptoKitties.[76]

Regulation

See also: 2020s commodities boom

In the United States, the proposed Digital Commodities Consumer Protection Act would treat Ethereum and other cryptocurrencies as commodities, which could then be regulated by the Commodity Futures Trading Commission (CFTC).[77][78]

Notes

 Cryptocurrency do not have a formal ISO 4217 alpha-3 code. "ETH" is informal only

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 "Bitcoin Basics" (PDF). Commodity Futures Trading Commission. December 2019. Retrieved 21 December 2022.

A blockchain is a distributed ledger with growing lists of records (blocks) that are securely linked together via cryptographic hashes.[1][2][3][4] Each block contains a cryptographic hash of the previous block, a timestamp, and transaction data (generally represented as a Merkle tree, where data nodes are represented by leaves). Since each block contains information about the previous block, they effectively form a chain (compare linked list data structure), with each additional block linking to the ones before it. Consequently, blockchain transactions are irreversible in that, once they are recorded, the data in any given block cannot be altered retroactively without altering all subsequent blocks.

Blockchains are typically managed by a peer-to-peer (P2P) computer network for use as a public distributed ledger, where nodes collectively adhere to a consensus algorithm protocol to add and validate new transaction blocks. Although blockchain records are not unalterable, since blockchain forks are possible, blockchains may be considered secure by design and exemplify a distributed computing system with high Byzantine fault tolerance.[5]

A blockchain was created by a person (or group of people) using the name (or pseudonym) Satoshi Nakamoto in 2008 to serve as the public distributed ledger for bitcoin cryptocurrency transactions, based on previous work by Stuart Haber, W. Scott Stornetta, and Dave Bayer.[6] The implementation of the blockchain within bitcoin made it the first digital currency to solve the double-spending problem without the need of a trusted authority or central server. The bitcoin design has inspired other applications[3][2] and blockchains that are readable by the public and are widely used by cryptocurrencies. The blockchain may be considered a type of payment rail.[7]

Private blockchains have been proposed for business use. Computerworld called the marketing of such privatized blockchains without a proper security model "snake oil";[8] however, others have argued that permissioned blockchains, if carefully designed, may be more decentralized and therefore more secure in practice than permissionless ones.[4][9]

History

Bitcoin, Ethereum and Litecoin transactions per day (January 2011 – January 2021)

Cryptographer David Chaum first proposed a blockchain-like protocol in his 1982 dissertation "Computer Systems Established, Maintained, and Trusted by Mutually Suspicious Groups."[10] Further work on a cryptographically secured chain of blocks was described in 1991 by Stuart Haber and W. Scott Stornetta.[4][11] They wanted to implement a system wherein document timestamps could not be tampered with. In 1992, Haber, Stornetta, and Dave Bayer incorporated Merkle trees into the design, which improved its efficiency by allowing several document certificates to be collected into one block.[4][12] Under their company Surety, their document certificate hashes have been published in The New York Times every week since 1995.[13]

The first decentralized blockchain was conceptualized by a person (or group of people) known as Satoshi Nakamoto in 2008. Nakamoto improved the design in an important way using a Hashcash-like method to timestamp blocks without requiring them to be signed by a trusted party and introducing a difficulty parameter to stabilize the rate at which blocks are added to the chain.[4] The design was implemented the following year by Nakamoto as a core component of the cryptocurrency bitcoin, where it serves as the public ledger for all transactions on the network.[3]

In August 2014, the bitcoin blockchain file size, containing records of all transactions that have occurred on the network, reached 20 GB (gigabytes).[14] In January 2015, the size had grown to almost 30 GB, and from January 2016 to January 2017, the bitcoin blockchain grew from 50 GB to 100 GB in size. The ledger size had exceeded 200 GB by early 2020.[15]

The words block and chain were used separately in Satoshi Nakamoto's original paper, but were eventually popularized as a single word, blockchain, by 2016.[16]

According to Accenture, an application of the diffusion of innovations theory suggests that blockchains attained a 13.5% adoption rate within financial services in 2016, therefore reaching the early adopters' phase.[17] Industry trade groups joined to create the Global Blockchain Forum in 2016, an initiative of the Chamber of Digital Commerce.

In May 2018, Gartner found that only 1% of CIOs indicated any kind of blockchain adoption within their organisations, and only 8% of CIOs were in the short-term "planning or [looking at] active experimentation with blockchain".[18] For the year 2019 Gartner reported 5% of CIOs believed blockchain technology was a 'game-changer' for their business.[19]

Structure and design

Blockchain formation. The main chain (black) consists of the longest series of blocks from the genesis block (green) to the current block. Orphan blocks (purple) exist outside of the main chain.

A blockchain is a decentralized, distributed, and often public, digital ledger consisting of records called blocks that are used to record transactions across many computers so that any involved block cannot be altered retroactively, without the alteration of all subsequent blocks.[3][20] This allows the participants to verify and audit transactions independently and relatively inexpensively.[21] A blockchain database is managed autonomously using a peer-to-peer network and a distributed timestamping server. They are authenticated by mass collaboration powered by collective self-interests.[22] Such a design facilitates robust workflow where participants' uncertainty regarding data security is marginal. The use of a blockchain removes the characteristic of infinite reproducibility from a digital asset. It confirms that each unit of value was transferred only once, solving the long-standing problem of double-spending. A blockchain has been described as a value-exchange protocol.[23] A blockchain can maintain title rights because, when properly set up to detail the exchange agreement, it provides a record that compels offer and acceptance.[citation needed]

Logically, a blockchain can be seen as consisting of several layers:[24]

infrastructure (hardware)

networking (node discovery, information propagation[25] and verification)

consensus (proof of work, proof of stake)

data (blocks, transactions)

application (smart contracts/decentralized applications, if applicable)

Blocks

Blocks hold batches of valid transactions that are hashed and encoded into a Merkle tree.[3] Each block includes the cryptographic hash of the prior block in the blockchain, linking the two. The linked blocks form a chain.[3] This iterative process confirms the integrity of the previous block, all the way back to the initial block, which is known as the genesis block (Block 0).[26][27] To assure the integrity of a block and the data contained in it, the block is usually digitally signed.[28]

Sometimes separate blocks can be produced concurrently, creating a temporary fork. In addition to a secure hash-based history, any blockchain has a specified algorithm for scoring different versions of the history so that one with a higher score can be selected over others. Blocks not selected for inclusion in the chain are called orphan blocks.[27] Peers supporting the database have different versions of the history from time to time. They keep only the highest-scoring version of the database known to them. Whenever a peer receives a higher-scoring version (usually the old version with a single new block added) they extend or overwrite their own database and retransmit the improvement to their peers. There is never an absolute guarantee that any particular entry will remain in the best version of history forever. Blockchains are typically built to add the score of new blocks onto old blocks and are given incentives to extend with new blocks rather than overwrite old blocks. Therefore, the probability of an entry becoming superseded decreases exponentially[29] as more blocks are built on top of it, eventually becoming very low.[3][30]: ch. 08 [31] For example, bitcoin uses a proof-of-work system, where the chain with the most cumulative proof-of-work is considered the valid one by the network. There are a number of methods that can be used to demonstrate a sufficient level of computation. Within a blockchain the computation is carried out redundantly rather than in the traditional segregated and parallel manner.[32]

Block time

The block time is the average time it takes for the network to generate one extra block in the blockchain. By the time of block completion, the included data becomes verifiable. In cryptocurrency, this is practically when the transaction takes place, so a shorter block time means faster transactions. The block time for Ethereum is set to between 14 and 15 seconds, while for bitcoin it is on average 10 minutes.[33]

Hard forks

This section is an excerpt from Fork (blockchain) § Hard fork.[edit]

A hard fork is a change to the blockchain protocol that is not backward-compatible and requires all users to upgrade their software in order to continue participating in the network. In a hard fork, the network splits into two separate versions: one that follows the new rules and one that follows the old rules.

For example, Ethereum was hard-forked in 2016 to "make whole" the investors in The DAO, which had been hacked by exploiting a vulnerability in its code. In this case, the fork resulted in a split creating Ethereum and Ethereum Classic chains. In 2014 the Nxt community was asked to consider a hard fork that would have led to a rollback of the blockchain records to mitigate the effects of a theft of 50 million NXT from a major cryptocurrency exchange. The hard fork proposal was rejected, and some of the funds were recovered after negotiations and ransom payment. Alternatively, to prevent a permanent split, a majority of nodes using the new software may return to the old rules, as was the case of bitcoin split on 12 March 2013.[34]

A more recent hard-fork example is of Bitcoin in 2017, which resulted in a split creating Bitcoin Cash.[35] The network split was mainly due to a disagreement in how to increase the transactions per second to accommodate for demand.[36]

Decentralization

By storing data across its peer-to-peer network, the blockchain eliminates some risks that come with data being held centrally.[3] The decentralized blockchain may use ad hoc message passing and distributed networking.[37]

In a so-called "51% attack" a central entity gains control of more than half of a network and can then manipulate that specific blockchain record at will, allowing double-spending.[38]

Blockchain security methods include the use of public-key cryptography.[39]: 5  A public key (a long, random-looking string of numbers) is an address on the blockchain. Value tokens sent across the network are recorded as belonging to that address. A private key is like a password that gives its owner access to their digital assets or the means to otherwise interact with the various capabilities that blockchains now support. Data stored on the blockchain is generally considered incorruptible.[3]

Every node in a decentralized system has a copy of the blockchain. Data quality is maintained by massive database replication[40] and computational trust. No centralized "official" copy exists and no user is "trusted" more than any other.[39] Transactions are broadcast to the network using the software. Messages are delivered on a best-effort basis. Early blockchains rely on energy-intensive mining nodes to validate transactions,[27] add them to the block they are building, and then broadcast the completed block to other nodes.[30]: ch. 08  Blockchains use various time-stamping schemes, such as proof-of-work, to serialize changes.[41] Later consensus methods include proof of stake.[27] The growth of a decentralized blockchain is accompanied by the risk of centralization because the computer resources required to process larger amounts of data become more expensive.[42]

Finality

Finality is the level of confidence that the well-formed block recently appended to the blockchain will not be revoked in the future (is "finalized") and thus can be trusted. Most distributed blockchain protocols, whether proof of work or proof of stake, cannot guarantee the finality of a freshly committed block, and instead rely on "probabilistic finality": as the block goes deeper into a blockchain, it is less likely to be altered or reverted by a newly found consensus.[43]

Byzantine fault tolerance-based proof-of-stake protocols purport to provide so called "absolute finality": a randomly chosen validator proposes a block, the rest of validators vote on it, and, if a supermajority decision approves it, the block is irreversibly committed into the blockchain.[43] A modification of this method, an "economic finality", is used in practical protocols, like the Casper protocol used in Ethereum: validators which sign two different blocks at the same position in the blockchain are subject to "slashing", where their leveraged stake is forfeited.[43]

Openness

Open blockchains are more user-friendly than some traditional ownership records, which, while open to the public, still require physical access to view. Because all early blockchains were permissionless, controversy has arisen over the blockchain definition. An issue in this ongoing debate is whether a private system with verifiers tasked and authorized (permissioned) by a central authority should be considered a blockchain.[44][45][46][47][48] Proponents of permissioned or private chains argue that the term "blockchain" may be applied to any data structure that batches data into time-stamped blocks. These blockchains serve as a distributed version of multiversion concurrency control (MVCC) in databases.[49] Just as MVCC prevents two transactions from concurrently modifying a single object in a database, blockchains prevent two transactions from spending the same single output in a blockchain.[50]: 30–31  Opponents say that permissioned systems resemble traditional corporate databases, not supporting decentralized data verification, and that such systems are not hardened against operator tampering and revision.[44][46] Nikolai Hampton of Computerworld said that "many in-house blockchain solutions will be nothing more than cumbersome databases," and "without a clear security model, proprietary blockchains should be eyed with suspicion."[8][51]

Permissionless (public) blockchain

An advantage to an open, permissionless, or public, blockchain network is that guarding against bad actors is not required and no access control is needed.[29] This means that applications can be added to the network without the approval or trust of others, using the blockchain as a transport layer.[29]

Bitcoin and other cryptocurrencies currently secure their blockchain by requiring new entries to include proof of work. To prolong the blockchain, bitcoin uses Hashcash puzzles. While Hashcash was designed in 1997 by Adam Back, the original idea was first proposed by Cynthia Dwork and Moni Naor and Eli Ponyatovski in their 1992 paper "Pricing via Processing or Combatting Junk Mail".

In 2016, venture capital investment for blockchain-related projects was weakening in the USA but increasing in China.[52] Bitcoin and many other cryptocurrencies use open (public) blockchains. As of April 2018, bitcoin has the highest market capitalization.

Permissioned (private) blockchain

See also: Distributed ledger

Permissioned blockchains use an access control layer to govern who has access to the network.[53] It has been argued that permissioned blockchains can guarantee a certain level of decentralization, if carefully designed, as opposed to permissionless blockchains, which are often centralized in practice.[9]

Disadvantages of permissioned blockchain

Nikolai Hampton argued in Computerworld that "There is also no need for a '51 percent' attack on a private blockchain, as the private blockchain (most likely) already controls 100 percent of all block creation resources. If you could attack or damage the blockchain creation tools on a private corporate server, you could effectively control 100 percent of their network and alter transactions however you wished."[8] This has a set of particularly profound adverse implications during a financial crisis or debt crisis like the financial crisis of 2007–08, where politically powerful actors may make decisions that favor some groups at the expense of others,[54] and "the bitcoin blockchain is protected by the massive group mining effort. It's unlikely that any private blockchain will try to protect records using gigawatts of computing power — it's time-consuming and expensive."[8] He also said, "Within a private blockchain there is also no 'race'; there's no incentive to use more power or discover blocks faster than competitors. This means that many in-house blockchain solutions will be nothing more than cumbersome databases."[8]

Blockchain analysis

The analysis of public blockchains has become increasingly important with the popularity of bitcoin, Ethereum, litecoin and other cryptocurrencies.[55] A blockchain, if it is public, provides anyone who wants access to observe and analyse the chain data, given one has the know-how. The process of understanding and accessing the flow of crypto has been an issue for many cryptocurrencies, crypto exchanges and banks.[56][57] The reason for this is accusations of blockchain-enabled cryptocurrencies enabling illicit dark market trade of drugs, weapons, money laundering, etc.[58] A common belief has been that cryptocurrency is private and untraceable, thus leading many actors to use it for illegal purposes. This is changing and now specialised tech companies provide blockchain tracking services, making crypto exchanges, law-enforcement and banks more aware of what is happening with crypto funds and fiat-crypto exchanges. The development, some argue, has led criminals to prioritise the use of new cryptos such as Monero.[59][60][61]

Standardisation

In April 2016, Standards Australia submitted a proposal to the International Organization for Standardization to consider developing standards to support blockchain technology. This proposal resulted in the creation of ISO Technical Committee 307, Blockchain and Distributed Ledger Technologies.[62] The technical committee has working groups relating to blockchain terminology, reference architecture, security and privacy, identity, smart contracts, governance and interoperability for blockchain and DLT, as well as standards specific to industry sectors and generic government requirements.[63][non-primary source needed] More than 50 countries are participating in the standardization process together with external liaisons such as the Society for Worldwide Interbank Financial Telecommunication (SWIFT), the European Commission, the International Federation of Surveyors, the International Telecommunication Union (ITU) and the United Nations Economic Commission for Europe (UNECE).[63]

Many other national standards bodies and open standards bodies are also working on blockchain standards.[64] These include the National Institute of Standards and Technology[65] (NIST), the European Committee for Electrotechnical Standardization[66] (CENELEC), the Institute of Electrical and Electronics Engineers[67] (IEEE), the Organization for the Advancement of Structured Information Standards (OASIS), and some individual participants in the Internet Engineering Task Force[68] (IETF).

Centralized blockchain

Although most of blockchain implementation are decentralized and distributed, Oracle launched a centralized blockchain table feature in Oracle 21c database. The Blockchain Table in Oracle 21c database is a centralized blockchain which provide immutable feature. Compared to decentralized blockchains, centralized blockchains normally can provide a higher throughput and lower latency of transactions than consensus-based distributed blockchains.[69][70]

Types

Currently, there are at least four types of blockchain networks — public blockchains, private blockchains, consortium blockchains and hybrid blockchains.

Public blockchains

A public blockchain has absolutely no access restrictions. Anyone with an Internet connection can send transactions to it as well as become a validator (i.e., participate in the execution of a consensus protocol).[71][self-published source?] Usually, such networks offer economic incentives for those who secure them and utilize some type of a proof-of-stake or proof-of-work algorithm.

Some of the largest, most known public blockchains are the bitcoin blockchain and the Ethereum blockchain.

Private blockchains

A private blockchain is permissioned.[53] One cannot join it unless invited by the network administrators. Participant and validator access is restricted. To distinguish between open blockchains and other peer-to-peer decentralized database applications that are not open ad-hoc compute clusters, the terminology Distributed Ledger (DLT) is normally used for private blockchains.

Hybrid blockchains

A hybrid blockchain has a combination of centralized and decentralized features.[72] The exact workings of the chain can vary based on which portions of centralization and decentralization are used.

Sidechains

A sidechain is a designation for a blockchain ledger that runs in parallel to a primary blockchain.[73][74] Entries from the primary blockchain (where said entries typically represent digital assets) can be linked to and from the sidechain; this allows the sidechain to otherwise operate independently of the primary blockchain (e.g., by using an alternate means of record keeping, alternate consensus algorithm, etc.).[75][better source needed]

Consortium blockchain

A consortium blockchain is a type of blockchain that combines elements of both public and private blockchains. In a consortium blockchain, a group of organizations come together to create and operate the blockchain, rather than a single entity. The consortium members jointly manage the blockchain network and are responsible for validating transactions. Consortium blockchains are permissioned, meaning that only certain individuals or organizations are allowed to participate in the network. This allows for greater control over who can access the blockchain and helps to ensure that sensitive information is kept confidential.

Consortium blockchains are commonly used in industries where multiple organizations need to collaborate on a common goal, such as supply chain management or financial services. One advantage of consortium blockchains is that they can be more efficient and scalable than public blockchains, as the number of nodes required to validate transactions is typically smaller. Additionally, consortium blockchains can provide greater security and reliability than private blockchains, as the consortium members work together to maintain the network. Some examples of consortium blockchains include Quorum and Hyperledger.[76]

Uses

Bitcoin's transactions are recorded on a publicly viewable blockchain.

Blockchain technology can be integrated into multiple areas. The primary use of blockchains is as a distributed ledger for cryptocurrencies such as bitcoin; there were also a few other operational products that had matured from proof of concept by late 2016.[52] As of 2016, some businesses have been testing the technology and conducting low-level implementation to gauge blockchain's effects on organizational efficiency in their back office.[77]

In 2019, it was estimated that around $2.9 billion were invested in blockchain technology, which represents an 89% increase from the year prior. Additionally, the International Data Corp has estimated that corporate investment into blockchain technology will reach $12.4 billion by 2022.[78] Furthermore, According to PricewaterhouseCoopers (PwC), the second-largest professional services network in the world, blockchain technology has the potential to generate an annual business value of more than $3 trillion by 2030. PwC's estimate is further augmented by a 2018 study that they have conducted, in which PwC surveyed 600 business executives and determined that 84% have at least some exposure to utilizing blockchain technology, which indicates a significant demand and interest in blockchain technology.[79]

In 2019, the BBC World Service radio and podcast series Fifty Things That Made the Modern Economy identified blockchain as a technology that would have far-reaching consequences for economics and society. The economist and Financial Times journalist and broadcaster Tim Harford discussed why the underlying technology might have much wider applications and the challenges that needed to be overcome.[80] His first broadcast was on June 29, 2019.

The number of blockchain wallets quadrupled to 40 million between 2016 and 2020.[81]

A paper published in 2022 discussed the potential use of blockchain technology in sustainable management.[82]

Cryptocurrencies

Main article: Cryptocurrency

Most cryptocurrencies use blockchain technology to record transactions. For example, the bitcoin network and Ethereum network are both based on blockchain.

The criminal enterprise Silk Road, which operated on Tor, utilized cryptocurrency for payments, some of which the US federal government has seized through research on the blockchain and forfeiture.[83]

Governments have mixed policies on the legality of their citizens or banks owning cryptocurrencies. China implements blockchain technology in several industries including a national digital currency which launched in 2020.[84] To strengthen their respective currencies, Western governments including the European Union and the United States have initiated similar projects.[85]

Smart contracts

Main article: Smart contract

Blockchain-based smart contracts are proposed contracts that can be partially or fully executed or enforced without human interaction.[86] One of the main objectives of a smart contract is automated escrow. A key feature of smart contracts is that they do not need a trusted third party (such as a trustee) to act as an intermediary between contracting entities — the blockchain network executes the contract on its own. This may reduce friction between entities when transferring value and could subsequently open the door to a higher level of transaction automation.[87] An IMF staff discussion from 2018 reported that smart contracts based on blockchain technology might reduce moral hazards and optimize the use of contracts in general. But "no viable smart contract systems have yet emerged." Due to the lack of widespread use, their legal status was unclear.[88][89]

Financial services

According to Reason, many banks have expressed interest in implementing distributed ledgers for use in banking and are cooperating with companies creating private blockchains,[90][91][92] and according to a September 2016 IBM study, this is occurring faster than expected.[93]

Banks are interested in this technology not least because it has the potential to speed up back office settlement systems.[94] Moreover, as the blockchain industry has reached early maturity institutional appreciation has grown that it is, practically speaking, the infrastructure of a whole new financial industry, with all the implications which that entails.[95]

Banks such as UBS are opening new research labs dedicated to blockchain technology in order to explore how blockchain can be used in financial services to increase efficiency and reduce costs.[96][97]

Berenberg, a German bank, believes that blockchain is an "overhyped technology" that has had a large number of "proofs of concept", but still has major challenges, and very few success stories.[98]

The blockchain has also given rise to initial coin offerings (ICOs) as well as a new category of digital asset called security token offerings (STOs), also sometimes referred to as digital security offerings (DSOs).[99] STO/DSOs may be conducted privately or on public, regulated stock exchange and are used to tokenize traditional assets such as company shares as well as more innovative ones like intellectual property, real estate,[100] art, or individual products. A number of companies are active in this space providing services for compliant tokenization, private STOs, and public STOs.

Games

Main article: Blockchain game

Blockchain technology, such as cryptocurrencies and non-fungible tokens (NFTs), has been used in video games for monetization. Many live-service games offer in-game customization options, such as character skins or other in-game items, which the players can earn and trade with other players using in-game currency. Some games also allow for trading of virtual items using real-world currency, but this may be illegal in some countries where video games are seen as akin to gambling, and has led to gray market issues such as skin gambling, and thus publishers typically have shied away from allowing players to earn real-world funds from games.[101] Blockchain games typically allow players to trade these in-game items for cryptocurrency, which can then be exchanged for money.[102]

The first known game to use blockchain technologies was CryptoKitties, launched in November 2017, where the player would purchase NFTs with Ethereum cryptocurrency, each NFT consisting of a virtual pet that the player could breed with others to create offspring with combined traits as new NFTs.[103][102] The game made headlines in December 2017 when one virtual pet sold for more than US$100,000.[104] CryptoKitties also illustrated scalability problems for games on Ethereum when it created significant congestion on the Ethereum network in early 2018 with approximately 30% of all Ethereum transactions[clarification needed] being for the game.[105][106]

By the early 2020s, there had not been a breakout success in video games using blockchain, as these games tend to focus on using blockchain for speculation instead of more traditional forms of gameplay, which offers limited appeal to most players. Such games also represent a high risk to investors as their revenues can be difficult to predict.[102] However, limited successes of some games, such as Axie Infinity during the COVID-19 pandemic, and corporate plans towards metaverse content, refueled interest in the area of GameFi, a term describing the intersection of video games and financing typically backed by blockchain currency, in the second half of 2021.[107] Several major publishers, including Ubisoft, Electronic Arts, and Take Two Interactive, have stated that blockchain and NFT-based games are under serious consideration for their companies in the future.[108]

In October 2021, Valve Corporation banned blockchain games, including those using cryptocurrency and NFTs, from being hosted on its Steam digital storefront service, which is widely used for personal computer gaming, claiming that this was an extension of their policy banning games that offered in-game items with real-world value. Valve's prior history with gambling, specifically skin gambling, was speculated to be a factor in the decision to ban blockchain games.[109] Journalists and players responded positively to Valve's decision as blockchain and NFT games have a reputation for scams and fraud among most PC gamers,[101][109] and Epic Games, which runs the Epic Games Store in competition to Steam, said that they would be open to accepted blockchain games in the wake of Valve's refusal.[110]

Supply chain

This section needs to be updated. Please help update this article to reflect recent events or newly available information. (August 2023)

There have been several different efforts to employ blockchains in supply chain management.

Precious commodities mining — Blockchain technology has been used for tracking the origins of gemstones and other precious commodities. In 2016, The Wall Street Journal reported that the blockchain technology company Everledger was partnering with IBM's blockchain-based tracking service to trace the origin of diamonds to ensure that they were ethically mined.[111] As of 2019, the Diamond Trading Company (DTC) has been involved in building a diamond trading supply chain product called Tracr.[112]

Food supply — As of 2018, Walmart and IBM were running a trial to use a blockchain-backed system for supply chain monitoring for lettuce and spinach — all nodes of the blockchain were administered by Walmart and were located on the IBM cloud.[113]

Fashion industry — There is an opaque relationship between brands, distributors, and customers in the fashion industry, which will prevent the sustainable and stable development of the fashion industry. Blockchain makes up for this shortcoming and makes information transparent, solving the difficulty of sustainable development of the industry.[114]

Motor vehicles — Mercedes-Benz and partner Icertis developed a blockchain prototype used to facilitate consistent documentation of contracts along the supply chain so that the ethical standards and contractual obligations required of its direct suppliers can be passed on to second tier suppliers and beyond.[115][116] In another project, the company uses blockchain technology to track the emissions of climate-relevant gases and the amount of secondary material along the supply chain for its battery cell manufacturers.[117]

Domain names

There are several different efforts to offer domain name services via the blockchain. These domain names can be controlled by the use of a private key, which purports to allow for uncensorable websites. This would also bypass a registrar's ability to suppress domains used for fraud, abuse, or illegal content.[118]

Namecoin is a cryptocurrency that supports the ".bit" top-level domain (TLD). Namecoin was forked from bitcoin in 2011. The .bit TLD is not sanctioned by ICANN, instead requiring an alternative DNS root.[118] As of 2015, .bit was used by 28 websites, out of 120,000 registered names.[119] Namecoin was dropped by OpenNIC in 2019, due to malware and potential other legal issues.[120] Other blockchain alternatives to ICANN include The Handshake Network,[119] EmerDNS, and Unstoppable Domains.[118]

Specific TLDs include ".eth", ".luxe", and ".kred", which are associated with the Ethereum blockchain through the Ethereum Name Service (ENS). The .kred TLD also acts as an alternative to conventional cryptocurrency wallet addresses as a convenience for transferring cryptocurrency.[121]

Other uses

Blockchain technology can be used to create a permanent, public, transparent ledger system for compiling data on sales, tracking digital use and payments to content creators, such as wireless users[122] or musicians.[123] The Gartner 2019 CIO Survey reported 2% of higher education respondents had launched blockchain projects and another 18% were planning academic projects in the next 24 months.[124] In 2017, IBM partnered with ASCAP and PRS for Music to adopt blockchain technology in music distribution.[125] Imogen Heap's Mycelia service has also been proposed as a blockchain-based alternative "that gives artists more control over how their songs and associated data circulate among fans and other musicians."[126][127]

New distribution methods are available for the insurance industry such as peer-to-peer insurance, parametric insurance and microinsurance following the adoption of blockchain.[128][129] The sharing economy and IoT are also set to benefit from blockchains because they involve many collaborating peers.[130] The use of blockchain in libraries is being studied with a grant from the U.S. Institute of Museum and Library Services.[131]

Other blockchain designs include Hyperledger, a collaborative effort from the Linux Foundation to support blockchain-based distributed ledgers, with projects under this initiative including Hyperledger Burrow (by Monax) and Hyperledger Fabric (spearheaded by IBM).[132][133][134] Another is Quorum, a permissioned private blockchain by JPMorgan Chase with private storage, used for contract applications.[135]

Oracle introduced a blockchain table feature in its Oracle 21c database.[69][70]

Blockchain is also being used in peer-to-peer energy trading.[136][137][138]

Blockchain could be used in detecting counterfeits by associating unique identifiers to products, documents and shipments, and storing records associated with transactions that cannot be forged or altered.[139][140] It is however argued that blockchain technology needs to be supplemented with technologies that provide a strong binding between physical objects and blockchain systems,[141] as well as provisions for content creator verification ala KYC standards.[142] The EUIPO established an Anti-Counterfeiting Blockathon Forum, with the objective of "defining, piloting and implementing" an anti-counterfeiting infrastructure at the European level.[143][144] The Dutch Standardisation organisation NEN uses blockchain together with QR Codes to authenticate certificates.[145]

2022 Jan 30 Beijing and Shanghai are among the cities designated by China to trial blockchain applications.[146]

Blockchain interoperability

With the increasing number of blockchain systems appearing, even only those that support cryptocurrencies, blockchain interoperability is becoming a topic of major importance. The objective is to support transferring assets from one blockchain system to another blockchain system. Wegner[147] stated that "interoperability is the ability of two or more software components to cooperate despite differences in language, interface, and execution platform". The objective of blockchain interoperability is therefore to support such cooperation among blockchain systems, despite those kinds of differences.

There are already several blockchain interoperability solutions available.[148] They can be classified into three categories: cryptocurrency interoperability approaches, blockchain engines, and blockchain connectors.

Several individual IETF participants produced the draft of a blockchain interoperability architecture.[149]

Energy consumption concerns

Some cryptocurrencies use blockchain mining — the peer-to-peer computer computations by which transactions are validated and verified. This requires a large amount of energy. In June 2018, the Bank for International Settlements criticized the use of public proof-of-work blockchains for their high energy consumption.[150][151][152]

Early concern over the high energy consumption was a factor in later blockchains such as Cardano (2017), Solana (2020) and Polkadot (2020) adopting the less energy-intensive proof-of-stake model. Researchers have estimated that Bitcoin consumes 100,000 times as much energy as proof-of-stake networks.[153][154]

In 2021, a study by Cambridge University determined that Bitcoin (at 121 terawatt-hours per year) used more electricity than Argentina (at 121TWh) and the Netherlands (109TWh).[155] According to Digiconomist, one bitcoin transaction required 708 kilowatt-hours of electrical energy, the amount an average U.S. household consumed in 24 days.[156]

In February 2021, U.S. Treasury secretary Janet Yellen called Bitcoin "an extremely inefficient way to conduct transactions", saying "the amount of energy consumed in processing those transactions is staggering".[157] In March 2021, Bill Gates stated that "Bitcoin uses more electricity per transaction than any other method known to mankind", adding "It's not a great climate thing."[158]

Nicholas Weaver, of the International Computer Science Institute at the University of California, Berkeley, examined blockchain's online security, and the energy efficiency of proof-of-work public blockchains, and in both cases found it grossly inadequate.[159][160] The 31TWh-45TWh of electricity used for bitcoin in 2018 produced 17-23 million tonnes of CO2.[161][162] By 2022, the University of Cambridge and Digiconomist estimated that the two largest proof-of-work blockchains, Bitcoin and Ethereum, together used twice as much electricity in one year as the whole of Sweden, leading to the release of up to 120 million tonnes of CO2 each year.[163]

Some cryptocurrency developers are considering moving from the proof-of-work model to the proof-of-stake model.[164]

Academic research

Blockchain panel discussion at the first IEEE Computer Society TechIgnite conference

In October 2014, the MIT Bitcoin Club, with funding from MIT alumni, provided undergraduate students at the Massachusetts Institute of Technology access to $100 of bitcoin. The adoption rates, as studied by Catalini and Tucker (2016), revealed that when people who typically adopt technologies early are given delayed access, they tend to reject the technology.[165] Many universities have founded departments focusing on crypto and blockchain, including MIT, in 2017. In the same year, Edinburgh became "one of the first big European universities to launch a blockchain course", according to the Financial Times.[166]

Adoption decision

Motivations for adopting blockchain technology (an aspect of innovation adoptation) have been investigated by researchers. For example, Janssen, et al. provided a framework for analysis,[167] and Koens & Poll pointed out that adoption could be heavily driven by non-technical factors.[168] Based on behavioral models, Li[169] has discussed the differences between adoption at the individual level and organizational levels.

Collaboration

Scholars in business and management have started studying the role of blockchains to support collaboration.[170][171] It has been argued that blockchains can foster both cooperation (i.e., prevention of opportunistic behavior) and coordination (i.e., communication and information sharing). Thanks to reliability, transparency, traceability of records, and information immutability, blockchains facilitate collaboration in a way that differs both from the traditional use of contracts and from relational norms. Contrary to contracts, blockchains do not directly rely on the legal system to enforce agreements.[172] In addition, contrary to the use of relational norms, blockchains do not require a trust or direct connections between collaborators.

Blockchain and internal audit

External video

video icon Blockchain Basics & Cryptography, Gary Gensler, Massachusetts Institute of Technology, 0:30[173]

The need for internal audits to provide effective oversight of organizational efficiency will require a change in the way that information is accessed in new formats.[174] Blockchain adoption requires a framework to identify the risk of exposure associated with transactions using blockchain. The Institute of Internal Auditors has identified the need for internal auditors to address this transformational technology. New methods are required to develop audit plans that identify threats and risks. The Internal Audit Foundation study, Blockchain and Internal Audit, assesses these factors.[175] The American Institute of Certified Public Accountants has outlined new roles for auditors as a result of blockchain.[176]

Journals

Main article: Ledger (journal)

In September 2015, the first peer-reviewed academic journal dedicated to cryptocurrency and blockchain technology research, Ledger, was announced. The inaugural issue was published in December 2016.[177] The journal covers aspects of mathematics, computer science, engineering, law, economics and philosophy that relate to cryptocurrencies.[178][179] The journal encourages authors to digitally sign a file hash of submitted papers, which are then timestamped into the bitcoin blockchain. Authors are also asked to include a personal bitcoin address on the first page of their papers for non-repudiation purposes.[180]

See also

icon Economics portal

Changelog – a record of all notable changes made to a project

Checklist – an informational aid used to reduce failure

Economics of digitization

List of blockchains

Privacy and blockchain

Version control – a record of all changes (mostly of software project) in a form of a graph

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 Balagurusamy, V. S. K.; Cabral, C.; Coomaraswamy, S.; Delamarche, E.; Dillenberger, D. N.; Dittmann, G.; Friedman, D.; Gökçe, O.; Hinds, N.; Jelitto, J.; Kind, A. (1 March 2019). "Crypto anchors". IBM Journal of Research and Development. 63 (2/3): 4:1–4:12. doi:10.1147/JRD.2019.2900651. ISSN 0018-8646. S2CID 201109790.

 Jung, Seung Wook (23 June 2021). Lee, Robert (ed.). A Novel Authentication System for Artwork Based on Blockchain (eBook). 20th IEEE/ACIS International Summer Semi-Virtual Conference on Computer and Information Science (ICIS 2021). Studies in Computational Intelligence. Vol. 985. Springer. p. 159 – via Google Books.

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Further reading

Crosby, Michael; Nachiappan; Pattanayak, Pradhan; Verma, Sanjeev; Kalyanaraman, Vignesh (16 October 2015). BlockChain Technology: Beyond Bitcoin (PDF) (Report). Sutardja Center for Entrepreneurship & Technology Technical Report. University of California, Berkeley. Retrieved 19 March 2017.

Jaikaran, Chris (28 February 2018). Blockchain: Background and Policy Issues. Washington, DC: Congressional Research Service. Archived from the original on 2 December 2018. Retrieved 2 December 2018.

Kakavand, Hossein; De Sevres, Nicolette Kost; Chilton, Bart (12 October 2016). The Blockchain Revolution: An Analysis of Regulation and Technology Related to Distributed Ledger Technologies (Report). Luther Systems & DLA Piper. SSRN 2849251.

Mazonka, Oleg (29 December 2016). "Blockchain: Simple Explanation" (PDF). Journal of Reference. Archived from the original (PDF) on 7 August 2017. Retrieved 29 December 2016.

Tapscott, Don; Tapscott, Alex (2016). Blockchain Revolution: How the Technology Behind Bitcoin Is Changing Money, Business and the World. London: Portfolio Penguin. ISBN 978-0-241-23785-4. OCLC 971395169.

Saito, Kenji; Yamada, Hiroyuki (June 2016). What's So Different about Blockchain? Blockchain is a Probabilistic State Machine. IEEE 36th International Conference on Distributed Computing Systems Workshops. International Conference on Distributed Computing Systems Workshops (Icdcs). Nara, Nara, Japan: IEEE. pp. 168–75. doi:10.1109/ICDCSW.2016.28. ISBN 978-1-5090-3686-8. ISSN 2332-5666.

Raval, Siraj (2016). Decentralized Applications: Harnessing Bitcoin's Blockchain Technology. Oreilly. ISBN 9781491924549.

Bashir, Imran (2017). Mastering Blockchain. Packt Publishing, Ltd. ISBN 978-1-78712-544-5. OCLC 967373845.

Knirsch, Fabian; Unterweger, Andread; Engel, Dominik (2019). "Implementing a blockchain from scratch: why, how, and what we learned". EURASIP Journal on Information Security. 2019. doi:10.1186/s13635-019-0085-3. S2CID 84837476.

D. Puthal, N. Malik, S. P. Mohanty, E. Kougianos, and G. Das, "Everything you Wanted to Know about the Blockchain", IEEE Consumer Electronics Magazine, Volume 7, Issue 4, July 2018, pp. 06–14.

David L. Portilla, David J. Kappos, Minh Van Ngo, Sasha Rosenthal-Larrea, John D. Buretta and Christopher K. Fargo, Cravath, Swaine & Moore LLP, "Blockchain in the Banking Sector: A Review of the Landscape and Opportunities", Harvard Law School of Corporate Governance, posted on Friday, January 28, 2022

A smart contract is a computer program or a transaction protocol that is intended to automatically execute, control or document events and actions according to the terms of a contract or an agreement.[1][2][3][4] The objectives of smart contracts are the reduction of need for trusted intermediators, arbitration costs, and fraud losses, as well as the reduction of malicious and accidental exceptions.[5][2] Smart contracts are commonly associated with cryptocurrencies, and the smart contracts introduced by Ethereum are generally considered a fundamental building block for decentralized finance (DeFi) and NFT applications.[6][7]

Vending machines are mentioned as the oldest piece of technology equivalent to smart contract implementation.[3] The original Ethereum white paper by Vitalik Buterin in 2014[8] describes the Bitcoin protocol as a weak version of the smart contract concept as originally defined by Nick Szabo, and proposed a stronger version based on the Solidity language, which is Turing complete. Since Bitcoin,[clarification needed] various cryptocurrencies have supported programming languages which allow for more advanced smart contracts between untrusted parties.[9]

A smart contract should not be confused with a smart legal contract, which refers to a traditional, natural-language, legally-binding agreement that has selected terms expressed and implemented in machine-readable code.[10][11][12]

Etymology

Smart contracts were first proposed in the early 1990s by Nick Szabo, who coined the term, using it to refer to "a set of promises, specified in digital form, including protocols within which the parties perform on these promises".[13][14] In 1998, the term was used to describe objects in rights management service layer of the system The Stanford Infobus, which was a part of Stanford Digital Library Project.[1]

Legal status of smart contracts

See also: Regulation of algorithms

A smart contract does not typically constitute a valid binding agreement at law,[15] although a smart legal contract is intended to be both executable by a machine and legally enforceable.[16] [10][11][12]

Smart contracts are not legal agreements, but rather means of performing obligations deriving from agreements that can be executed automatically by a computer program or a transaction protocol,[15] such as technological means for the automation of payment obligations[17] or obligations consisting in the transfer of tokens or cryptocurrencies. Some scholars have argued that the imperative or declarative nature of programming languages would impact the legal validity of smart contracts.[18]

Since the 2015 launch of the Ethereum blockchain,[19] the term "smart contract" has been more specifically applied toward the notion of general purpose computation that takes place on a blockchain or distributed ledger. The US National Institute of Standards and Technology describes a "smart contract" as a "collection of code and data (sometimes referred to as functions and state) that is deployed using cryptographically signed transactions on the blockchain network".[20] In this interpretation, used for example by the Ethereum Foundation[8] or IBM,[21] a smart contract is not necessarily related to the classical concept of a contract, but can be any kind of computer program. A smart contract also can be regarded as a secured stored procedure, as its execution and codified effects (like the transfer of value between parties) are strictly enforced and cannot be manipulated; after a transaction with specific contract details is stored into a blockchain or distributed ledger, it cannot be changed. That's because the actual execution of contracts is controlled and audited by the platform, not by arbitrary server-side programs connecting to the platform.[22][23]

In 2017, by implementing the Decree on Development of Digital Economy, Belarus has become the first-ever[dubious – discuss] country to legalize smart contracts. Belarusian lawyer Denis Aleinikov is considered to be the author of a smart contract legal concept introduced by the decree.[24][better source needed]

In 2018, a US Senate report said: "While smart contracts might sound new, the concept is rooted in basic contract law. Usually, the judicial system adjudicates contractual disputes and enforces terms, but it is also common to have another arbitration method, especially for international transactions. With smart contracts, a program enforces the contract built into the code."[25] A number of states in the US have passed legislation on the use of smart contracts, such as Arizona,[26] Nevada,[27] Tennessee,[28] and Wyoming.[29] And in April 2020, Iowa's House of Representatives passed a bill legally recognizing smart contracts in the state.[30]

In April 2021, the UK Jurisdiction Taskforce (UKJT) published the Digital Dispute Resolution Rules (the Digital DR Rules) to help enable the rapid resolution of blockchain and crypto legal disputes in Britain.[31]

Workings

Similar to a transfer of value on a blockchain, deployment of a smart contract on a blockchain occurs by sending a transaction from a wallet for the blockchain.[32] The transaction includes the compiled code for the smart contract as well as a special receiver address.[32] That transaction must then be included in a block that is added to the blockchain, at which point the smart contract's code will execute to establish the initial state of the smart contract.[32] Byzantine fault-tolerant algorithms secure the smart contract in a decentralized way from attempts to tamper with it. Once a smart contract is deployed, it cannot be updated.[33] Smart contracts on a blockchain can store arbitrary state and execute arbitrary computations. End clients interact with a smart contract through transactions. Such transactions with a smart contract can invoke other smart contracts. These transactions might result in changing the state and sending coins from one smart contract to another or from one account to another.[33]

The most popular blockchain for running smart contracts is Ethereum.[34] On Ethereum, smart contracts are typically written in a Turing-complete programming language called Solidity,[35] and compiled into low-level bytecode to be executed by the Ethereum Virtual Machine.[36] Due to the halting problem and other security problems, Turing-completeness is considered to be a risk and is deliberately avoided by languages like Vyper.[37][38] Some of the other smart contract programming languages missing Turing-completeness are Simplicity, Scilla, Ivy and Bitcoin Script.[38] However, measurements in 2020 using regular expressions showed that only 35.3% of 53,757 Ethereum smart contracts at that time included recursions and loops — constructs connected to the halting problem.[39]

Several languages are designed to enable formal verification: Bamboo, IELE, Simplicity, Michelson (can be verified with Coq),[38] Liquidity (compiles to Michelson), Scilla, DAML and Pact.[37]

Notable examples of blockchain platforms supporting smart contracts include the following:

Name Description

Ethereum Implements a Turing-complete language on its blockchain, a prominent smart contract framework[40]

Bitcoin Provides a Turing-incomplete script language that allows the creation of custom smart contracts on top of Bitcoin like multisignature accounts, payment channels, escrows, time locks, atomic cross-chain trading, oracles, or multi-party lottery with no operator.[41]

Binance Smart Chain A blockchain platform for smart contracts

Cardano A blockchain platform for smart contracts, using proof of stake

Solana A blockchain platform for smart contracts

Avalanche A blockchain platform for smart contracts

Tron A blockchain platform for smart contracts

EOS.IO A blockchain platform for smart contracts

Tezos A blockchain platform modifying its own set of rules with minimal disruption to the network through an on-chain governance model

Processes on a blockchain are generally deterministic in order to ensure Byzantine fault-tolerance.[42] Nevertheless, real world application of smart contracts, such as lotteries and casinos, require secure randomness.[43] In fact, blockchain technology reduces the costs for conducting of a lottery and is therefore beneficial for the participants. Randomness on blockchain can be implemented by using block hashes or timestamps, oracles, commitment schemes, special smart contracts like RANDAO[44][45] and Quanta, as well as sequences from mixed strategy Nash equilibria.[42]

Applications

In 1998, Szabo proposed that smart contract infrastructure can be implemented by replicated asset registries and contract execution using cryptographic hash chains and Byzantine fault-tolerant replication.[46] Askemos implemented this approach in 2002[47][48] using Scheme (later adding SQLite[49][50]) as the contract script language.[51]

One proposal for using bitcoin for replicated asset registration and contract execution is called "colored coins".[52] Replicated titles for potentially arbitrary forms of property, along with replicated contract execution, are implemented in different projects.

As of 2015, UBS was experimenting with "smart bonds" that use the bitcoin blockchain[53] in which payment streams could hypothetically be fully automated, creating a self-paying instrument.[54]

Inheritance wishes could hypothetically be implemented automatically upon registration of a death certificate by means of smart contracts.[according to whom?][55][56] Birth certificates can also work together with smart contracts.[57][58]

Chris Snook of Inc.com suggests smart contracts could also be used to handle real estate transactions and could be used in the field of title records and in the public register.[59][60][61][62][63]

Seth Oranburg and Liya Palagashvili argue that smart contracts could also be used in employment contracts, especially temporary employment contracts, which according to them would benefit the employer.[64][65]

Smart contract on block chain technology for smart villages[66]

Security issues

The transactions data from a blockchain-based smart contract is visible to all users in the blockchain. The data provides cryptographic view of the transactions, however, this leads to a situation where bugs, including security holes, are visible to all yet may not be quickly fixed.[67] Such an attack, difficult to fix quickly, was successfully executed on The DAO in June 2016, draining approximately US$50 million worth of Ether at the time, while developers attempted to come to a solution that would gain consensus.[68] The DAO program had a time delay in place before the hacker could remove the funds; a hard fork of the Ethereum software was done to claw back the funds from the attacker before the time limit expired.[69] Other high-profile attacks include the Parity multisignature wallet attacks, and an integer underflow/overflow attack (2018), totaling over US$184 million.[70]

Issues in Ethereum smart contracts, in particular, include ambiguities and easy-but-insecure constructs in its contract language Solidity, compiler bugs, Ethereum Virtual Machine bugs, attacks on the blockchain network, the immutability of bugs and that there is no central source documenting known vulnerabilities, attacks and problematic constructs.[40]

Difference from smart legal contracts

Smart legal contracts are distinct from smart contracts. As mentioned above, a smart contract is not necessarily legally enforceable as a contract. On the other hand, a smart legal contract has all the elements of a legally enforceable contract in the jurisdiction in which it can be enforced and it can be enforced by a court or tribunal. Therefore, while every smart legal contract will contain some elements of a smart contract, not every smart contract will be a smart legal contract.[71]

There is no formal definition of a smart legal contract in the legal industry.[72]

A Ricardian contract is a type of smart legal contract.[citation needed]

See also

icon Law portal

icon Business and Economics portal

Code and Other Laws of Cyberspace

Decentralized application

Ethereum

Regulation by algorithms

Regulation of algorithms

Ricardian contract (a design pattern to capture the intent of the agreement of parties)[citation needed]

Loan

Secure multiparty computation

Transparency

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