Scott Stornetta, and Dave Bayer. 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   and blockchains that are readable by the public and are widely used by cryptocurrencies. The blockchain is considered a type of payment rail. Private blockchains have been proposed for business use. Computerworld called the marketing of such privatized blockchains without a proper security model " snake oil ";  however, others have argued that permissioned blockchains, if carefully designed, may be more decentralized and therefore more secure in practice than permissionless ones.
Scott Stornetta. In , 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. The first decentralized blockchain was conceptualized by a person or group of people known as Satoshi Nakamoto in 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.
In August , the bitcoin blockchain file size, containing records of all transactions that have occurred on the network, reached 20 GB gigabytes. The ledger size had exceeded GB by early The words block and chain were used separately in Satoshi Nakamoto's original paper, but were eventually popularized as a single word, blockchain, by According to Accenture , an application of the diffusion of innovations theory suggests that blockchains attained a A blockchain is a decentralized , distributed , and oftentimes 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.
They are authenticated by mass collaboration powered by collective self-interests. 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. Logically, a blockchain can be seen as consisting of several layers: .
Blocks hold batches of valid transactions that are hashed and encoded into a Merkle tree. The linked blocks form a chain. 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.
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  as more blocks are built on top of it, eventually becoming very low. 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.
The block time is the average time it takes for the network to generate one extra block in the blockchain. Some blockchains create a new block as frequently as every five seconds. 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.
A hard fork is a rule change such that the software validating according to the old rules will see the blocks produced according to the new rules as invalid. In case of a hard fork, all nodes meant to work in accordance with the new rules need to upgrade their software. If one group of nodes continues to use the old software while the other nodes use the new software, a permanent split can occur. For example, Ethereum was hard-forked in 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 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 By storing data across its peer-to-peer network , the blockchain eliminates a number of risks that come with data being held centrally. Peer-to-peer blockchain networks lack centralized points of vulnerability that computer crackers can exploit; likewise, it has no central point of failure. Blockchain security methods include the use of public-key cryptography.
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. Every node in a decentralized system has a copy of the blockchain.
Data quality is maintained by massive database replication  and computational trust. No centralized "official" copy exists and no user is "trusted" more than any other. Messages are delivered on a best-effort basis. Mining nodes validate transactions,  add them to the block they are building, and then broadcast the completed block to other nodes.
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.
These blockchains serve as a distributed version of multiversion concurrency control MVCC in databases. 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. 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. In , venture capital investment for blockchain-related projects was weakening in the USA but increasing in China. As of April [update] , bitcoin has the highest market capitalization. Permissioned blockchains use an access control layer to govern who has access to the network.
They do not rely on anonymous nodes to validate transactions nor do they benefit from the network effect. Nikolai Hampton pointed out 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 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 percent of their network and alter transactions however you wished. It's unlikely that any private blockchain will try to protect records using gigawatts of computing power — it's time-consuming and expensive.
This means that many in-house blockchain solutions will be nothing more than cumbersome databases. The analysis of public blockchains has become increasingly important with the popularity of bitcoin , Ethereum , litecoin and other cryptocurrencies. The process of understanding and accessing the flow of crypto has been an issue for many cryptocurrencies, crypto exchanges and banks.
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.
It is a key debate in cryptocurrency and ultimately in the blockchain. In April , Standards Australia submitted a proposal to the International Organization for Standardization to consider developing standards to support blockchain technology. Many other national standards bodies and open standards bodies are also working on blockchain standards.
Currently, there are at least four types of blockchain networks — public blockchains, private blockchains, consortium blockchains and hybrid 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. Some of the largest, most known public blockchains are the bitcoin blockchain and the Ethereum blockchain.
A private blockchain is permissioned. 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. A hybrid blockchain has a combination of centralized and decentralized features. A sidechain is a designation for a blockchain ledger that runs in parallel to a primary 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 Individual use of blockchain technology has also greatly increased since According to statistics in , there were more than 40 million blockchain wallets in in comparison to around 10 million blockchain wallets in Most cryptocurrencies use blockchain technology to record transactions.
For example, the bitcoin network and Ethereum network are both based on blockchain. On 8 May Facebook confirmed that it would open a new blockchain group  which would be headed by David Marcus , who previously was in charge of Messenger. Facebook's planned cryptocurrency platform, Libra now known as Diem , was formally announced on June 18, 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.
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 Blockchain-based smart contracts are proposed contracts that can be partially or fully executed or enforced without human interaction.
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.
But "no viable smart contract systems have yet emerged. According to Reason , many banks have expressed interest in implementing distributed ledgers for use in banking and are cooperating with companies creating private blockchains,    and according to a September IBM study, this is occurring faster than expected. Banks are interested in this technology not least because it has the potential to speed up back office settlement systems.
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. 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.
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. A number of companies are active in this space providing services for compliant tokenization, private STOs, and public STOs.
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.
The first known game to use blockchain technologies was CryptoKitties , launched in November , 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. By the early s, 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. In October , 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. There have been several different efforts to employ blockchains in supply chain management.
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.
Namecoin is a cryptocurrency that supports the ". Namecoin was forked from bitcoin in Specific TLDs include ". 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  or musicians. New distribution methods are available for the insurance industry such as peer-to-peer insurance , parametric insurance and microinsurance following the adoption of blockchain.
Institute of Museum and Library Services. 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. Blockchain is also being used in peer-to-peer energy trading. 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.
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  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. Several individual IETF participants produced the draft of a blockchain interoperability architecture.
Blockchain mining — the peer-to-peer computer computations by which transactions are validated and verified — requires a significant amount of energy. In June the Bank for International Settlements criticized the use of public proof-of-work blockchains for their high energy consumption. In February , U. 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.
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. Inside the cryptocurrency industry, concern about high energy consumption has led some companies to consider moving from the proof of work blockchain model to the less energy-intensive proof of stake model.
The adoption rates, as studied by Catalini and Tucker , revealed that when people who typically adopt technologies early are given delayed access, they tend to reject the technology. In the same year, Edinburgh became "one of the first big European universities to launch a blockchain course", according to the Financial Times.
Motivations for adopting blockchain technology an aspect of innovation adoptation have been investigated by researchers. For example, Janssen, et al. Scholars in business and management have started studying the role of blockchains to support collaboration. 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.
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. 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. In September , the first peer-reviewed academic journal dedicated to cryptocurrency and blockchain technology research, Ledger , was announced.
The inaugural issue was published in December 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. From Wikipedia, the free encyclopedia. Distributed data store for digital transactions.
For other uses, see Block chain disambiguation. See also: Distributed ledger. Main article: Cryptocurrency. Main article: Smart contract. Main article: Blockchain game. Main article: Ledger journal. Economics portal. Archived from the original on 21 May Retrieved 23 May The New York Times. Archived from the original on 22 May The Economist. Archived from the original on 3 July Retrieved 18 June The technology behind bitcoin lets people who do not know or trust each other build a dependable ledger.
This has implications far beyond the crypto currency. Bitcoin and cryptocurrency technologies: a comprehensive introduction. Princeton: Princeton University Press. ISBN January Harvard Business Review. Harvard University. Archived from the original on 18 January Retrieved 17 January The technology at the heart of bitcoin and other virtual currencies, blockchain is an open, distributed ledger that can record transactions between two parties efficiently and in a verifiable and permanent way.
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Purpose: This study attempts to determine whether or not Bitcoin prices are affected by real economic activity, financial markets, and foreign exchange markets; and whether Bitcoin has the potential … Expand. View 1 excerpt. View 1 excerpt, cites background. Global drivers of cryptocurrency infrastructure adoption. Anchoring the Value of Cryptocurrency. Nonprofit Reputation and Bitcoin Use. In recent years, cryptocurrencies, digital assets used as mediums of exchange that use cryptography to secure the creation and exchange of the currency, have gained in popularity.
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