Jump to content

Blockchain

Page semi-protected
From Wikipedia, the free encyclopedia

This is an old revision of this page, as edited by FrendlyBaratheon (talk | contribs) at 12:22, 6 August 2019 (→Video games: added point about specific token standards being developed optimized for a gaming use case, with reference to relevance of fungibility and non-fungibility for gaming assets). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

For other uses, see Block chain (disambiguation).

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.
Bitcoin network data

A blockchain,[1][2][3] originally block chain,[4][5] is a growing list of records, called blocks, that are linked using cryptography.[1][6] Each block contains a cryptographic hash of the previous block,[6] a timestamp, and transaction data (generally represented as a Merkle tree).

By design, a blockchain is resistant to modification of the data. It is "an open, distributed ledger that can record transactions between two parties efficiently and in a verifiable and permanent way".[7] For use as a distributed ledger, a blockchain is typically managed by a peer-to-peer network collectively adhering to a protocol for inter-node communication and validating new blocks. Once recorded, the data in any given block cannot be altered retroactively without alteration of all subsequent blocks, which requires consensus of the network majority. Although blockchain records are not unalterable, blockchains may be considered secure by design and exemplify a distributed computing system with high Byzantine fault tolerance. Decentralized consensus has therefore been claimed with a blockchain.[8]

Blockchain was invented by a person (or group of people) using the name Satoshi Nakamoto in 2008 to serve as the public transaction ledger of the cryptocurrency bitcoin.[1] The identity of Satoshi Nakamoto is unknown. The invention of the blockchain for 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,[1][3] and blockchains that are readable by the public are widely used by cryptocurrencies. Blockchain is considered a type of payment rail.[9] Private blockchains have been proposed for business use. Sources such as Computerworld called the marketing of such blockchains without a proper security model "snake oil".[10]

History

Bitcoin transactions (January 2009 – September 2017)

The first work on a cryptographically secured chain of blocks was described in 1991 by Stuart Haber and W. Scott Stornetta.[6][11] They wanted to implement a system where document timestamps could not be tampered with. In 1992, Bayer, Haber and Stornetta incorporated Merkle trees to the design, which improved its efficiency by allowing several document certificates to be collected into one block.[6][12]

The first 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 add blocks to the chain without requiring them to be signed by a trusted party.[6] 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.[1]

In August 2014, the bitcoin blockchain file size, containing records of all transactions that have occurred on the network, reached 20 GB (gigabytes).[13] 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 words block and chain were used separately in Satoshi Nakamoto's original paper, but were eventually popularized as a single word, blockchain, by 2016.

Smart contracts that run on a blockchain, for example ones that "creat[e] invoices that pay themselves when a shipment arrives or share certificates that automatically send their owners dividends if profits reach a certain level."[1] require an off-chain oracle to access any "external data or events based on time or market conditions [that need] to interact with the blockchain."[14]

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.[15] 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'.[16]

Structure

A blockchain is a decentralized, distributed and public digital ledger that is used to record transactions across many computers so that any involved record cannot be altered retroactively, without the alteration of all subsequent blocks.[1][17] This allows the participants to verify and audit transactions independently and relatively inexpensively.[18] 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.[19] 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.[20] 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.

Blocks

Blocks hold batches of valid transactions that are hashed and encoded into a Merkle tree.[1] Each block includes the cryptographic hash of the prior block in the blockchain, linking the two. The linked blocks form a chain.[1] This iterative process confirms the integrity of the previous block, all the way back to the original genesis block.[21]

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.[21] 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 the 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[22] as more blocks are built on top of it, eventually becoming very low.[1][23]: ch. 08 [24] 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.[25]

Block time

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. 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 10 minutes.[citation needed]

Hard forks

This section is transcluded from Fork (blockchain). (edit | history)

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.[26]

A more recent hard-fork example is of Bitcoin in 2017, which resulted in a split creating Bitcoin Cash.[27] The network split was mainly due to a disagreement in how to increase the transactions per second to accommodate for demand.[28]

Decentralization

By storing data across its peer-to-peer network, the blockchain eliminates a number of risks that come with data being held centrally.[1] The decentralized blockchain may use ad-hoc message passing and distributed networking.

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.[4]: 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.[1]

Every node in a decentralized system has a copy of the blockchain. Data quality is maintained by massive database replication[8] and computational trust. No centralized "official" copy exists and no user is "trusted" more than any other.[4] Transactions are broadcast to the network using software. Messages are delivered on a best-effort basis. Mining nodes validate transactions,[21] add them to the block they are building, and then broadcast the completed block to other nodes.[23]: ch. 08  Blockchains use various time-stamping schemes, such as proof-of-work, to serialize changes.[29] Alternative consensus methods include proof-of-stake.[21] 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.[30]

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.[31][32][33][34][35] 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.[36] 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.[37]: 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.[31][33] 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."[10][38]

Permissionless

The great advantage to an open, permissionless, or public, blockchain network is that guarding against bad actors is not required and no access control is needed.[22] This means that applications can be added to the network without the approval or trust of others, using the blockchain as a transport layer.[22]

Bitcoin and other cryptocurrencies currently secure their blockchain by requiring new entries to include a 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".

Financial companies have not prioritised decentralized blockchains.[citation needed]

In 2016, venture capital investment for blockchain-related projects was weakening in the USA but increasing in China.[39] 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.[40] In contrast to public blockchain networks, validators on private blockchain networks are vetted by the network owner. They do not rely on anonymous nodes to validate transactions nor do they benefit from the network effect.[citation needed] Permissioned blockchains can also go by the name of 'consortium' blockchains.[41][better source needed]

Disadvantages of private blockchain

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 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."[10] 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,[42][43] 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."[10] 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."[10]

Blockchain analysis

The analysis of public blockchains has become increasingly important with the popularity of bitcoin, Ethereum, litecoin and other cryptocurrencies.[44] 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.[45][46] The reason for this is accusations of blockchain enabled cryptocurrencies enabling illicit dark market trade of drugs, weapons, money laundering etc.[47] 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 use of new cryptos such as Monero.[48][49][50] The question is about public accessibility of blockchain data and the personal privacy of the very same data. It is a key debate in cryptocurrency and ultimately in blockchain.[51]

Uses

Blockchain technology can be integrated into multiple areas. The primary use of blockchains today is as a distributed ledger for cryptocurrencies, most notably bitcoin. There are a few operational products maturing from proof of concept by late 2016.[39] Businesses have been thus far reluctant to place blockchain at the core of the business structure.[52]

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. On 8 May 2018 Facebook confirmed that it is opening a new blockchain group[53] which will be headed by David Marcus who previously was in charge of Messenger. According to The Verge Facebook is planning to launch its own cryptocurrency for facilitating payments on the platform.[54]

Smart contracts

Main article: Smart contract

Blockchain-based smart contracts are proposed contracts that could be partially or fully executed or enforced without human interaction.[55] One of the main objectives of a smart contract is automated escrow. An IMF staff discussion 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 is unclear.[56][57]

Financial services

Major portions of the financial industry are implementing distributed ledgers for use in banking,[58][59][60] and according to a September 2016 IBM study, this is occurring faster than expected.[61]

Banks are interested in this technology because it has potential to speed up back office settlement systems.[62]

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.[63][64]

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.[65]

Video games

A blockchain game CryptoKitties, launched in November 2017.[66] The game made headlines in December 2017 when a cryptokitty character - an in-game virtual pet - was sold for more than US$100,000.[67] CryptoKitties illustrated scalability problems for games on Ethereum when it created significant congestion on the Ethereum network with about 30% of all Ethereum transactions being for the game.[68]

Cryptokitties also demonstrated how blockchains can be used to catalog game assets (digital assets).[69]

Specific token standards have been created to support the use of blockchain in gaming. These include the ERC-721 standard of CryptoKitties for non-fungible tokens, and the more recent ERC-1155 standard, for the creation of both fungible (e.g. an in-game currency) and non-fungible tokens (e.g. a set of rare armour) on the blockchain.

Use of blockchain in the creation of game assets can provide advantages to gamers. These include true ownership (assets are tied an individual's blockchain address rather than accessed from a centralized game server), transparency (blockchain explorers can be used to confirm total supply of various game assets), and interoperability (by being read from a decentralized public ledger, blockchain assets are open for any developers to integrate into their own game via blockchain if they choose to)[70].

Supply chain

There are a number of efforts and industry organizations working to employ blockchains in supply chain logistics and supply chain management.

The Blockchain in Transport Alliance (BiTA) works to develop open standards for supply chains.[citation needed]

Everledger is one of the inaugural clients of IBM's blockchain-based tracking service.[71]

Walmart and IBM are running a trial to use a blockchain-backed system for supply chain monitoring — all nodes of the blockchain are administered by Walmart and are located on the IBM cloud.[72]

Hyperledger Grid develops open components for blockchain supply chain solutions.[73][74]

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[75] or musicians.[76] In 2017, IBM partnered with ASCAP and PRS for Music to adopt blockchain technology in music distribution.[77] Imogen Heap's Mycelia service has also been proposed as blockchain-based alternative "that gives artists more control over how their songs and associated data circulate among fans and other musicians."[78][79]

New distribution methods are available for the insurance industry such as peer-to-peer insurance, parametric insurance and microinsurance following the adoption of blockchain.[80][81] The sharing economy and IoT are also set to benefit from blockchains because they involve many collaborating peers.[82] Online voting is another application of the blockchain.[83][84]

Other designs include:

  • Hyperledger is a cross-industry 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)[85]
  • Quorum – a permissionable private blockchain by JPMorgan Chase with private storage, used for contract applications[86]
  • Tezos, decentralized voting.[37]: 94 
  • Proof of Existence is an online service that verifies the existence of computer files as of a specific time[87]

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).[88][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.[40] One cannot join it unless invited by the network administrators. Participant and validator access is restricted.

This type of blockchains can be considered a middle-ground for companies that are interested in the blockchain technology in general but are not comfortable with a level of control offered by public networks. Typically, they seek to incorporate blockchain into their accounting and record-keeping procedures without sacrificing autonomy and running the risk of exposing sensitive data to the public internet.[citation needed]

Hybrid blockchains

A hybrid blockchain[89] simply explained is a combination between different characteristics both public and private blockchains have by design. It allows to determine what information stays private and what information is made public. Further decentralization in relation to primarily centralized private blockchains can be achieved in various ways. Instead of keeping transactions inside their own network of community run or private nodes, the hash (with or without payload) can be posted on completely decentralized blockchains such as bitcoin. Dragonchain uses Interchain[90] to host transactions on other blockchains. This allows users to operate on different blockchains, where they can selectively share data or business logic. Other blockchains like Wanchain use interoperability mechanisms such as bridges.[91][92] By submitting the hash of a transaction (with or without the sensitive business logic) on public blockchains like bitcoin or Ethereum, some of the privacy and blockchain concerns are resolved, as no personal identifiable information is stored on a public blockchain. Depending on the hybrid blockchain its architecture, multicloud solutions allow to store data in compliance with General Data Protection Regulation and other geographical limitations while also leveraging bitcoin's global hashpower to decentralize transactions.

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.[93]

Energy use of proof-of-work blockchains

External videos
video icon Cryptocurrencies: looking beyond the hype, Hyun Song Shin, Bank for International Settlements, 2:48[94]
video icon Blockchains and Cryptocurrencies: Burn It With Fire, Nicholas Weaver, Berkeley School of Information, 49:47, lecture begins at 3:05[95]

The Bank for International Settlements has criticized the public proof-of-work blockchains for high energy consumption.[96][94][97]

Nicholas Weaver, of the International Computer Science Institute at the University of California, Berkeley examines blockchain's online security, and the energy efficiency of proof-of-work public blockchains, and in both cases finds it grossly inadequate.[95][98]

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.[99] The journal covers aspects of mathematics, computer science, engineering, law, economics and philosophy that relate to cryptocurrencies such as bitcoin.[100][101]

The journal encourages authors to digitally sign a file hash of submitted papers, which will then be timestamped into the bitcoin blockchain. Authors are also asked to include a personal bitcoin address in the first page of their papers.[102]

See also

References

  1. ^ a b c d e f g h i j k l "Blockchains: The great chain of being sure about things". The Economist. 31 October 2015. Archived from the original on 3 July 2016. Retrieved 18 June 2016. The technology behind bitcoin lets people who do not know or trust each other build a dependable ledger. This has implications far beyond the crypto currency. {{cite journal}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  2. ^ Morris, David Z. (15 May 2016). "Leaderless, Blockchain-Based Venture Capital Fund Raises $100 Million, And Counting". Fortune. Archived from the original on 21 May 2016. Retrieved 23 May 2016. {{cite news}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  3. ^ a b Popper, Nathan (21 May 2016). "A Venture Fund With Plenty of Virtual Capital, but No Capitalist". The New York Times. Archived from the original on 22 May 2016. Retrieved 23 May 2016. {{cite news}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  4. ^ a b c Brito, Jerry; Castillo, Andrea (2013). Bitcoin: A Primer for Policymakers (PDF) (Report). Fairfax, VA: Mercatus Center, George Mason University. Archived from the original (PDF) on 21 September 2013. Retrieved 22 October 2013. {{cite report}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  5. ^ Trottier, Leo (18 June 2016). "original-bitcoin". github. Archived from the original (self-published code collection) on 17 April 2016. Retrieved 18 June 2016. This is a historical repository of Satoshi Nakamoto's original bit coin sourcecode {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  6. ^ a b c d e Narayanan, Arvind; Bonneau, Joseph; Felten, Edward; Miller, Andrew; Goldfeder, Steven (2016). Bitcoin and cryptocurrency technologies: a comprehensive introduction. Princeton: Princeton University Press. ISBN 978-0-691-17169-2.
  7. ^ Iansiti, Marco; Lakhani, Karim R. (January 2017). "The Truth About Blockchain". Harvard Business Review. Harvard University. Archived from the original on 18 January 2017. Retrieved 17 January 2017. The technology at the heart of bitcoin and other virtual currencies, blockchain is an open, distributed ledger that can record transactions between two parties efficiently and in a verifiable and permanent way. {{cite news}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  8. ^ a b Raval, Siraj (2016). "What Is a Decentralized Application?". Decentralized Applications: Harnessing Bitcoin's Blockchain Technology. O'Reilly Media, Inc. pp. 1–2. ISBN 978-1-4919-2452-5. OCLC 968277125. Retrieved 6 November 2016 – via Google Books.
  9. ^ "Blockchain may finally disrupt payments from Micropayments to credit cards to SWIFT". dailyfintech.com. 10 February 2018. Retrieved 18 November 2018.
  10. ^ a b c d e Hampton, Nikolai (5 September 2016). "Understanding the blockchain hype: Why much of it is nothing more than snake oil and spin". Computerworld. Archived from the original on 6 September 2016. Retrieved 5 September 2016. {{cite magazine}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  11. ^ Haber, Stuart; Stornetta, W. Scott (January 1991). "How to time-stamp a digital document". Journal of Cryptology. 3 (2): 99–111. CiteSeerX 10.1.1.46.8740. doi:10.1007/bf00196791.
  12. ^ Bayer, Dave; Haber, Stuart; Stornetta, W. Scott (March 1992). Improving the Efficiency and Reliability of Digital Time-Stamping. Vol. 2. pp. 329–334. CiteSeerX 10.1.1.71.4891. doi:10.1007/978-1-4613-9323-8_24. ISBN 978-1-4613-9325-2. {{cite book}}: |journal= ignored (help)
  13. ^ Nian, Lam Pak; Chuen, David LEE Kuo (2015). "A Light Touch of Regulation for Virtual Currencies". In Chuen, David LEE Kuo (ed.). Handbook of Digital Currency: Bitcoin, Innovation, Financial Instruments, and Big Data. Academic Press. p. 319. ISBN 978-0-12-802351-8.
  14. ^ Project Bletchley Whitepaper Archived 11 January 2017 at the Wayback Machine, Microsoft, 2016-09-19. Retrieved 2016-12-24.
  15. ^ "The future of blockchain in 8 charts". Raconteur. 27 June 2016. Archived from the original on 2 December 2016. Retrieved 3 December 2016. {{cite news}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  16. ^ "Hype Killer - Only 1% of Companies Are Using Blockchain, Gartner Reports | Artificial Lawyer". Artificial Lawyer. 4 May 2018. Retrieved 22 May 2018.
  17. ^ Armstrong, Stephen (7 November 2016). "Move over Bitcoin, the blockchain is only just getting started". Wired. Archived from the original on 8 November 2016. Retrieved 9 November 2016. {{cite news}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  18. ^ Catalini, Christian; Gans, Joshua S. (23 November 2016). "Some Simple Economics of the Blockchain". doi:10.2139/ssrn.2874598. SSRN 2874598. {{cite journal}}: Cite journal requires |journal= (help)
  19. ^ Tapscott, Don; Tapscott, Alex (8 May 2016). "Here's Why Blockchains Will Change the World". Fortune. Archived from the original on 13 November 2016. Retrieved 16 November 2016. {{cite magazine}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  20. ^ Bheemaiah, Kariappa (January 2015). "Block Chain 2.0: The Renaissance of Money". Wired. Archived from the original on 14 November 2016. Retrieved 13 November 2016. {{cite magazine}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  21. ^ a b c d Bhaskar, Nirupama Devi; Chuen, David LEE Kuo (2015). "Bitcoin Mining Technology". Handbook of Digital Currency. pp. 45–65. doi:10.1016/B978-0-12-802117-0.00003-5. ISBN 978-0-12-802117-0.
  22. ^ a b c Antonopoulos, Andreas (20 February 2014). "Bitcoin security model: trust by computation". Radar. O'Reilly. Archived from the original on 31 October 2016. Retrieved 19 November 2016. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  23. ^ a b Antonopoulos, Andreas M. (2014). Mastering Bitcoin. Unlocking Digital Cryptocurrencies. Sebastopol, CA: O'Reilly Media. ISBN 978-1449374037. Archived from the original on 1 December 2016. Retrieved 3 November 2015. {{cite book}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  24. ^ Nakamoto, Satoshi (October 2008). "Bitcoin: A Peer-to-Peer Electronic Cash System" (PDF). bitcoin.org. Archived from the original (PDF) on 20 March 2014. Retrieved 28 April 2014. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  25. ^ "Permissioned Blockchains". Explainer. Monax. Archived from the original on 20 November 2016. Retrieved 20 November 2016. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  26. ^ Lee, Timothy (12 March 2013). "Major glitch in Bitcoin network sparks sell-off; price temporarily falls 23%". Arstechnica. Archived from the original on 20 April 2013. Retrieved 25 February 2018.
  27. ^ Smith, Oli (21 January 2018). "Bitcoin price RIVAL: Cryptocurrency 'faster than bitcoin' will CHALLENGE market leaders". Express. Archived from the original on 28 March 2019. Retrieved 6 April 2021.
  28. ^ "Bitcoin split in two, here's what that means". CNN. 1 August 2017. Archived from the original on 27 February 2018. Retrieved 7 April 2021.
  29. ^ Kopfstein, Janus (12 December 2013). "The Mission to Decentralize the Internet". The New Yorker. Archived from the original on 31 December 2014. Retrieved 30 December 2014. The network's 'nodes' — users running the bitcoin software on their computers — collectively check the integrity of other nodes to ensure that no one spends the same coins twice. All transactions are published on a shared public ledger, called the 'block chain.' {{cite journal}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  30. ^ Gervais, Arthur; Karame, Ghassan O.; Capkun, Vedran; Capkun, Srdjan. "Is Bitcoin a Decentralized Currency?". InfoQ. InfoQ & IEEE computer society. Archived from the original on 10 October 2016. Retrieved 11 October 2016. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  31. ^ a b Voorhees, Erik (30 October 2015). "It's All About the Blockchain". Money and State. Archived from the original on 1 November 2015. Retrieved 2 November 2015. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  32. ^ Reutzel, Bailey (13 July 2015). "A Very Public Conflict Over Private Blockchains". PaymentsSource. New York, NY: SourceMedia, Inc. Archived from the original on 21 April 2016. Retrieved 18 June 2016. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  33. ^ a b Casey, Michael J. (15 April 2015). "Moneybeat/BitBeat: Blockchains Without Coins Stir Tensions in Bitcoin Community". The Wall Street Journal. Archived from the original on 10 June 2016. Retrieved 18 June 2016. {{cite journal}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  34. ^ "The 'Blockchain Technology' Bandwagon Has A Lesson Left To Learn". dinbits.com. 3 November 2015. Archived from the original on 29 June 2016. Retrieved 18 June 2016. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  35. ^ DeRose, Chris (26 June 2015). "Why the Bitcoin Blockchain Beats Out Competitors". American Banker. Archived from the original on 30 March 2016. Retrieved 18 June 2016. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  36. ^ Greenspan, Gideon (19 July 2015). "Ending the bitcoin vs blockchain debate". multichain.com. Archived from the original on 8 June 2016. Retrieved 18 June 2016. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  37. ^ a b Tapscott, Don; Tapscott, Alex (May 2016). The Blockchain Revolution: How the Technology Behind Bitcoin is Changing Money, Business, and the World. ISBN 978-0-670-06997-2.
  38. ^ Barry, Levine (11 June 2018). "A new report bursts the blockchain bubble". MarTech. Retrieved 13 July 2018.
  39. ^ a b Ovenden, James. "Blockchain Top Trends In 2017". The Innovation Enterprise. Archived from the original on 30 November 2016. Retrieved 4 December 2016. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  40. ^ a b Bob Marvin (30 August 2017). "Blockchain: The Invisible Technology That's Changing the World". PC MAG Australia. ZiffDavis, LLC. Archived from the original on 25 September 2017. Retrieved 25 September 2017. {{cite news}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  41. ^ "Blockchains & Distributed Ledger Technologies". BlockchainHub. Archived from the original on 19 January 2018. Retrieved 18 January 2018. {{cite news}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  42. ^ Salsman, R.M. (19 September 2013). "The Financial Crisis Was A Failure Of Government, Not Free Markets". Forbes. Retrieved 8 May 2018.
  43. ^ O'Keeffe, M.; Terzi, A. (7 July 2015). "The political economy of financial crisis policy". Bruegel. Retrieved 8 May 2018.
  44. ^ Dr Garrick Hileman & Michel Rauchs (2017). "GLOBAL CRYPTOCURRENCY BENCHMARKING STUDY" (PDF). Cambridge Centre for Alternative Finance. University of Cambridge Judge Business School – via crowdfundinsider.
  45. ^ Raymaekers, Wim (March 2015). "Cryptocurrency Bitcoin: Disruption, challenges and opportunities". www.ingentaconnect.com. Retrieved 15 May 2019.
  46. ^ "Why Crypto Companies Still Can't Open Checking Accounts". 3 March 2019. Retrieved 4 June 2019.
  47. ^ Christian Brenig, Rafael Accorsi & Günter Müller (Spring 2015). "Economic Analysis of Cryptocurrency Backed Money Laundering". Association for Information Systems AIS Electronic Library (AISeL).
  48. ^ Greenberg, Andy (25 January 2017). "Monero, the Drug Dealer's Cryptocurrency of Choice, Is on Fire". Wired. ISSN 1059-1028. Retrieved 15 May 2019.
  49. ^ Orcutt, Mike. "It's getting harder to hide money in Bitcoin". MIT Technology Review. Retrieved 15 May 2019.
  50. ^ "Explainer: 'Privacy coin' Monero offers near total anonymity". Reuters. 15 May 2019. Retrieved 15 May 2019.
  51. ^ "An Untraceable Currency? Bitcoin Privacy Concerns - FinTech Weekly". FinTech Magazine Article. 7 April 2018. Retrieved 15 May 2019.
  52. ^ Katie Martin (27 September 2016). "CLS dips into blockchain to net new currencies". Financial Times. Archived from the original on 9 November 2016. Retrieved 7 November 2016. {{cite news}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  53. ^ Wagner, Kurt (8 May 2018). "Facebook is making its biggest executive shuffle in company history". Recode. Retrieved 25 September 2018.
  54. ^ Gartenberg, Chaim (11 May 2018). "Facebook reportedly plans to launch its own cryptocurrency". The Verge. Retrieved 25 September 2018.
  55. ^ Franco, Pedro (2014). Understanding Bitcoin: Cryptography, Engineering and Economics. John Wiley & Sons. p. 9. ISBN 978-1-119-01916-9. Archived from the original on 14 February 2017. Retrieved 4 January 2017 – via Google Books. {{cite book}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  56. ^ Governatori, Guido; Idelberger, Florian; Milosevic, Zoran; Riveret, Regis; Sartor, Giovanni; Xu, Xiwei (2018). "On legal contracts, imperative and declarative smart contracts, and blockchain systems". Artificial Intelligence and Law. 26 (4): 33. doi:10.1007/s10506-018-9223-3.
  57. ^ Virtual Currencies and Beyond: Initial Considerations (PDF). IMF Discussion Note. International Monetary Fund. 2016. p. 23. ISBN 978-1-5135-5297-2. Archived from the original (PDF) on 14 April 2018. Retrieved 19 April 2018. {{cite book}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  58. ^ Epstein, Jim (6 May 2016). "Is Blockchain Technology a Trojan Horse Behind Wall Street's Walled Garden?". Reason. Archived from the original on 8 July 2016. Retrieved 29 June 2016. mainstream misgivings about working with a system that's open for anyone to use. Many banks are partnering with companies building so-called private blockchains that mimic some aspects of Bitcoin's architecture except they're designed to be closed off and accessible only to chosen parties. ... [but some believe] that open and permission-less blockchains will ultimately prevail even in the banking sector simply because they're more efficient. {{cite news}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  59. ^ Redrup, Yolanda (29 June 2016). "ANZ backs private blockchain, but won't go public". Australia Financial Review. Archived from the original on 3 July 2016. Retrieved 7 July 2016. Blockchain networks can be either public or private. Public blockchains have many users and there are no controls over who can read, upload or delete the data and there are an unknown number of pseudonymous participants. In comparison, private blockchains also have multiple data sets, but there are controls in place over who can edit data and there are a known number of participants. {{cite news}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  60. ^ Shah, Rakesh (1 March 2018). "How Can The Banking Sector Leverage Blockchain Technology?". PostBox Communications. PostBox Communications Blog. Archived from the original on 17 March 2018. Banks preferably have a notable interest in utilizing Blockchain Technology because it is a great source to avoid fraudulent transactions. Blockchain is considered hassle free, because of the extra level of security it offers. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  61. ^ Kelly, Jemima (28 September 2016). "Banks adopting blockchain 'dramatically faster' than expected: IBM". Reuters. Reuters. Archived from the original on 28 September 2016. Retrieved 28 September 2016. {{cite news}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  62. ^ Arnold, Martin (23 September 2013). "IBM in blockchain project with China UnionPay". Financial Times. Archived from the original on 9 November 2016. Retrieved 7 November 2016. {{cite news}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  63. ^ "UBS leads team of banks working on blockchain settlement system". Reuters. 24 August 2016. Archived from the original on 19 May 2017. Retrieved 13 May 2017. {{cite news}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  64. ^ "Cryptocurrency Blockchain". capgemini.com. Archived from the original on 5 December 2016. Retrieved 13 May 2017. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  65. ^ Kelly, Jemima (31 October 2017). "Top banks and R3 build blockchain-based payments system". Reuters. Retrieved 9 July 2018.
  66. ^ "Internet firms try their luck at blockchain games". Asia Times. 22 February 2018. Retrieved 28 February 2018.
  67. ^ Evelyn Cheng (6 December 2017). "Meet CryptoKitties, the $100,000 digital beanie babies epitomizing the cryptocurrency mania". CNBC. Retrieved 28 February 2018.
  68. ^ Laignee Barron (13 February 2018). "CryptoKitties is Going Mobile. Can Ethereum Handle the Traffic?". Fortune. Retrieved 30 September 2018.
  69. ^ "CryptoKitties craze slows down transactions on Ethereum". 12 May 2017. Archived from the original on 12 January 2018. {{cite news}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  70. ^ "Enjin is Creating a Real-Life Ready Player One, and It's Powered by Blockchain". VentureBeat. 16 April 2019. Retrieved 5 August 2019.
  71. ^ Nash, Kim S. (14 July 2016). "IBM Pushes Blockchain into the Supply Chain". The Wall Street Journal. Archived from the original on 18 July 2016. Retrieved 24 July 2016. {{cite news}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  72. ^ Corkery, Michael; Popper, Nathaniel (24 September 2018). "From Farm to Blockchain: Walmart Tracks Its Lettuce". The New York Times. Retrieved 5 December 2018.
  73. ^ Mearian, Lucas (23 January 2019). "Grid, a new project from the Linux Foundation, will offer developers tools to create supply chain-specific applications running atop distributed ledger technology". ComputerWorld. Retrieved 8 March 2019.
  74. ^ Hyperledger (22 January 2019). "Announcing Hyperledger Grid, a new project to help build and deliver supply chain solutions!". Retrieved 8 March 2019.
  75. ^ K. Kotobi, and S. G. Bilen, "Secure Blockchains for Dynamic Spectrum Access : A Decentralized Database in Moving Cognitive Radio Networks Enhances Security and User Access", IEEE Vehicular Technology Magazine, 2018.
  76. ^ "Blockchain Could Be Music's Next Disruptor". 22 September 2016. Archived from the original on 23 September 2016. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  77. ^ "ASCAP, PRS and SACEM Join Forces for Blockchain Copyright System". Music Business Worldwide. 9 April 2017. Archived from the original on 10 April 2017. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  78. ^ Burchardi, K.; Harle, N. (20 January 2018). "The blockchain will disrupt the music business and beyond". Wired UK. Retrieved 8 May 2018.
  79. ^ Bartlett, Jamie (6 September 2015). "Imogen Heap: saviour of the music industry?". The Guardian. Archived from the original on 22 April 2016. Retrieved 18 June 2016. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  80. ^ Wang, Kevin; Safavi, Ali (29 October 2016). "Blockchain is empowering the future of insurance". Tech Crunch. AOL Inc. Archived from the original on 7 November 2016. Retrieved 7 November 2016. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  81. ^ Gatteschi, Valentina; Lamberti, Fabrizio; Demartini, Claudio; Pranteda, Chiara; Santamaría, Víctor (20 February 2018). "Blockchain and Smart Contracts for Insurance: Is the Technology Mature Enough?". Future Internet. 10 (2): 20. doi:10.3390/fi10020020.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  82. ^ "Blockchain reaction: Tech companies plan for critical mass" (PDF). Ernst & Young. p. 5. Archived from the original (PDF) on 14 November 2016. Retrieved 13 November 2016. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  83. ^ "Online Voting Platform FAQ's". Follow My Vote. Archived from the original on 27 October 2016. Retrieved 7 December 2016. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  84. ^ Chandra, Prabhul. "Reimagining Democracy: What if votes were a crypto-currency?". democracywithoutborders.org. Archived from the original on 5 February 2018. Retrieved 5 February 2018. {{cite news}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  85. ^ "IBM Blockchain based on Hyperledger Fabric from the Linux Foundation". IBM.com. 9 January 2018. Archived from the original on 7 December 2017. Retrieved 18 January 2018. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  86. ^ "Why J.P. Morgan Chase Is Building a Blockchain on Ethereum". Fortune. Archived from the original on 2 February 2017. Retrieved 24 January 2017. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  87. ^ Melanie Swan (2015). Blockchain: Blueprint for a New Economy. O'Reilly Media. pp. 38–39. ISBN 9781491920473.
  88. ^ "How Companies Can Leverage Private Blockchains to Improve Efficiency and Streamline Business Processes". Perfectial.
  89. ^ Blockchains and Enterprise: The Hybrid Approach to Adoption
  90. ^ Dragonchain Awarded U.S. Interchain™ Patent
  91. ^ Blockchain For Dummies - Book authored by Tiana Laurence
  92. ^ This Privacy-Focused Interoperable Blockchain Bridges Ethereum and Bitcoin
  93. ^ Catalini, Christian; Tucker, Catherine E. (11 August 2016). "Seeding the S-Curve? The Role of Early Adopters in Diffusion". doi:10.2139/ssrn.2822729. SSRN 2822729. {{cite journal}}: Cite journal requires |journal= (help)
  94. ^ a b Janda, Michael (18 June 2018). "Cryptocurrencies like bitcoin cannot replace money, says Bank for International Settlements". ABC (Australia). Retrieved 18 June 2018.
  95. ^ a b Illing, Sean (11 April 2018). "Why Bitcoin is bullshit, explained by an expert". Vox. Retrieved 17 July 2018.
  96. ^ Hyun Song Shin (June 2018). "Chapter V. Cryptocurrencies: looking beyond the hype" (PDF). BIS 2018 Annual Economic Report. Bank for International Settlements. Retrieved 19 June 2018. Put in the simplest terms, the quest for decentralised trust has quickly become an environmental disaster.
  97. ^ Hiltzik, Michael (18 June 2018). "Is this scathing report the death knell for bitcoin?". Los Angeles Times. Retrieved 19 June 2018.
  98. ^ Weaver, Nicholas. "Blockchains and Cryptocurrencies: Burn It With Fire". YouTube video. Berkeley School of Information. Retrieved 17 July 2018.
  99. ^ Extance, Andy (30 September 2015). "The future of cryptocurrencies: Bitcoin and beyond". Nature. 526 (7571): 21–23. doi:10.1038/526021a. ISSN 0028-0836. OCLC 421716612. PMID 26432223.
  100. ^ Ledger (eJournal / eMagazine, 2015). OCLC. OCLC 910895894.
  101. ^ Hertig, Alyssa (15 September 2015). "Introducing Ledger, the First Bitcoin-Only Academic Journal". Motherboard. Archived from the original on 10 January 2017. Retrieved 10 January 2017. {{cite web}}: Unknown parameter |dead-url= ignored (|url-status= suggested) (help)
  102. ^ Rizun, Peter R.; Wilmer, Christopher E.; Burley, Richard Ford; Miller, Andrew (2015). "How to Write and Format an Article for Ledger" (PDF). Ledger. 1 (1): 1–12. doi:10.5195/LEDGER.2015.1 (inactive 24 July 2019). ISSN 2379-5980. OCLC 910895894. Archived from the original (PDF) on 22 September 2015. Retrieved 11 January 2017. {{cite journal}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)CS1 maint: DOI inactive as of July 2019 (link) Open access icon

Further reading

Wikiversity has learning resources about Blockchain
Retrieved from "https://en.wikipedia.org/w/index.php?title=Blockchain&oldid=909601974"