The validity of each cryptocurrency's coins is provided by a blockchain. A blockchain is a continuously growing list of records, called blocks, which are linked and secured using cryptography. Each block typically contains a hash pointer as a link to a previous block, a timestamp and transaction data. By design, blockchains are inherently 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". For use as a distributed ledger, a blockchain is typically managed by a peer-to-peer network collectively adhering to a protocol for validating new blocks.


BitcoinsBitcoin walletmining
It is a decentralized digital currency without a central bank or single administrator that can be sent from user to user on the peer-to-peer bitcoin network without the need for intermediaries. Transactions are verified by network nodes through cryptography and recorded in a public distributed ledger called a blockchain. Bitcoin was invented in 2008 by an unknown person or group of people using the name Satoshi Nakamoto and started in 2009 when its source code was released as open-source software. Bitcoins are created as a reward for a process known as mining. They can be exchanged for other currencies, products, and services.

Decentralized computing

decentralizeddecentralisedAutonomy and decentralization
Later in 1982, for his PhD dissertation, he wrote about the need for decentralized computing services in the paper Computer Systems Established, Maintained and Trusted by Mutually Suspicious Groups. He would go on to launch the world's first digital payment system in 1990 called eCash. (Digicash) Based on a "grid model" a peer-to-peer system, or P2P system, is a collection of applications run on several local computers, which connect remotely to each other to complete a function or a task. There is no main operating system to which satellite systems are subordinate.

Consensus (computer science)

consensusconsensus problemsdistributed consensus
A fundamental problem in distributed computing and multi-agent systems is to achieve overall system reliability in the presence of a number of faulty processes. This often requires processes to agree on some data value that is needed during computation. Examples of applications of consensus include whether to commit a transaction to a database, agreeing on the identity of a leader, state machine replication, and atomic broadcasts. The real world applications include clock synchronization, PageRank, opinion formation, smart power grids, state estimation, control of UAVs (and multiple robots/agents in general), load balancing, blockchain and others.


onlinethe Internetweb
Free and fee-based services exist for all of these activities, using centralized servers and distributed peer-to-peer technologies. Some of these sources exercise more care with respect to the original artists' copyrights than others. Internet usage has been correlated to users' loneliness. Lonely people tend to use the Internet as an outlet for their feelings and to share their stories with others, such as in the "I am lonely will anyone speak to me" thread.


EtherERC-20Ethereum Virtual Machine
Ethereum is an open source, public, blockchain-based distributed computing platform and operating system featuring smart contract (scripting) functionality. It supports a modified version of Nakamoto consensus via transaction-based state transitions. Ether is a cryptocurrency generated by the Ethereum platform and used to compensate mining nodes for computations performed. Each Ethereum account has an ether balance and ether may be transferred from one account to another. Ethereum provides a decentralized virtual machine, the Ethereum Virtual Machine (EVM), which can execute scripts using an international network of public nodes.

Distributed networking

Distributed Network
A distributed network can also be agent-based, where what controls the agent or component is loosely defined, and the components can have either pre-configured or dynamic settings. Decentralization is where each computer on the network can be used for the computing task at hand, which is the opposite of the client/server model. Typically, only idle computers are used, and in this way, it is thought that networks are more efficient. Peer-to-peer (P2P) computation is based on a decentralized, distributed network, including the distributed ledger technology blockchain.

History of money

monetary historyabandonmentan international currency of the early ages
Its use of cryptography allowed the currency to have a trustless, fungible and tamper resistant distributed ledger called a blockchain. It became the first widely used decentralized, peer-to-peer, cryptocurrency. Other comparable systems had been proposed since the 1980s. The protocol proposed by Nakamoto solved what is known as the double-spending problem without the need of a trusted third-party. Since Bitcoin's inception, thousands of other cryptocurrencies have been introduced. In modern times economists have sought to classify the different types of money supply. The different measures of the money supply have been classified by various central banks, using the prefix "M".

Parallel computing

parallelparallel processingparallelism
A distributed computer (also known as a distributed memory multiprocessor) is a distributed memory computer system in which the processing elements are connected by a network. Distributed computers are highly scalable. The terms "concurrent computing", "parallel computing", and "distributed computing" have a lot of overlap, and no clear distinction exists between them. The same system may be characterized both as "parallel" and "distributed"; the processors in a typical distributed system run concurrently in parallel. A cluster is a group of loosely coupled computers that work together closely, so that in some respects they can be regarded as a single computer.


BitTorrent protocoltorrenttorrents
BitTorrent (abbreviated to BT) is a communication protocol for peer-to-peer file sharing (P2P) which is used to distribute data and electronic files over the Internet. BitTorrent is one of the most common protocols for transferring large files, such as digital video files containing TV shows or video clips or digital audio files containing songs. Peer-to-peer networks have been estimated to collectively account for approximately 43% to 70% of all Internet traffic (depending on location). In February 2013, BitTorrent was responsible for 3.35% of all worldwide bandwidth, more than half of the 6% of total bandwidth dedicated to file sharing.

Proof of work

proof-of-workproof-of-work systemreusable proof of work
But in Bitcoin double-spend protection is provided by a decentralized P2P protocol for tracking transfers of coins, rather than the hardware trusted computing function used by RPoW. Bitcoin has better trustworthiness because it is protected by computation. Bitcoins are "mined" using the Hashcash proof-of-work function by individual miners and verified by the decentralized nodes in the P2P bitcoin network. The difficulty is periodically adjusted to keep the block time around a target time. Within the Bitcoin community there are groups working together in mining pools. Some miners use ASICs (Application-Specific Integrated Circuit) for PoW.

Bitcoin network

bitcoin miningminingBitcoin protocol
The bitcoin network is a peer-to-peer payment network that operates on a cryptographic protocol. Users send and receive bitcoins, the units of currency, by broadcasting digitally signed messages to the network using bitcoin cryptocurrency wallet software. Transactions are recorded into a distributed, replicated public database known as the blockchain, with consensus achieved by a proof-of-work system called mining. Satoshi Nakamoto, the designer of bitcoin claimed that design and coding of bitcoin began in 2007. The project was released in 2009 as open source software. The network requires minimal structure to share transactions. An ad hoc decentralized network of volunteers is sufficient.

Node (networking)

nodenodesnetwork node
If the network in question is a distributed system, the nodes are clients, servers or peers. A peer may sometimes serve as client, sometimes server. In a peer-to-peer or overlay network, nodes that actively route data for the other networked devices as well as themselves are called supernodes. Distributed systems may sometimes use virtual nodes so that the system is not oblivious to the heterogeneity of the nodes. This issue is addressed with special algorithms, like consistent hashing, as it is the case in Amazon's Dynamo.

Cloud computing

cloudcloud-basedcloud services
Peer-to-peer—A distributed architecture without the need for central coordination. Participants are both suppliers and consumers of resources (in contrast to the traditional client–server model). Green computing. Cloud sandbox—A live, isolated computer environment in which a program, code or file can run without affecting the application in which it runs. Agility for organizations may be improved, as cloud computing may increase users' flexibility with re-provisioning, adding, or expanding technological infrastructure resources. Cost reductions are claimed by cloud providers. A public-cloud delivery model converts capital expenditures (e.g., buying servers) to operational expenditure.


C++ programming languageC++98C with Classes
When Stroustrup started working in AT&T Bell Labs, he had the problem of analyzing the UNIX kernel with respect to distributed computing. Remembering his Ph.D. experience, Stroustrup set out to enhance the C language with Simula-like features. C was chosen because it was general-purpose, fast, portable and widely used. As well as C and Simula's influences, other languages also influenced this new language, including ALGOL 68, Ada, CLU and ML. Initially, Stroustrup's "C with Classes" added features to the C compiler, Cpre, including classes, derived classes, strong typing, inlining and default arguments.

Satoshi Nakamoto

Dorian NakamotoNakamotoNakamoto, Satoshi
As part of the implementation, Nakamoto also devised the first blockchain database. In the process, Nakamoto was the first to solve the double-spending problem for digital currency using a peer-to-peer network. Nakamoto was active in the development of bitcoin up until December 2010. Many people have claimed, or have been claimed, to be "Satoshi." In October 2008, Nakamoto published a paper on the cryptography mailing list at describing the bitcoin digital currency. It was titled "Bitcoin: A Peer-to-Peer Electronic Cash System".

Libra (cryptocurrency)

LibraCalibraCalibra (company)
Initial reconciliation of transactions will be performed at each service partner, and the blockchain's distributed ledger will be used for reconciliation between service partners. The intent is to help prevent everyone but members of the Libra Association from trying to extract and analyse data from the distributed ledger. In contrast to cryptocurrencies such as bitcoin which use permissionless blockchains, Libra is not decentralized, relying on trust in the Libra Association as "a de facto central bank". . In September, Facebook announced that the reserve basket would be made up of: 50% United States dollar, 18% Euro, 14% Japanese yen, 11% Pound sterling and 7% Singapore dollar.

Privacy and blockchain

Private keys are used to access funds and personal wallets on the blockchain; they add a layer of identity authentication. When individuals wish to send money to other users, they must provide a digital signature that is produced when provided with the private key. This process protects against theft of funds. Blockchain technology arose from the creation of Bitcoin. In 2008, Satoshi Nakamoto released a paper describing the technology behind blockchains. In his paper, he explained a decentralized network that was characterized by peer-to-peer transactions involving cryptocurrencies or electronic money.

Decentralised system

decentralizeddecentralized systemdecentralised
Examples of decentralized systems: Examples of "decentralized system culture": Small Is Beautiful * Centralized system. Decentralization. Distributed system. Swarm intelligence. Network: peer-to-peer technology (e.g. Decentralized network 42). Monetary: Bitcoin. Animal communities: Red harvester ant.

Sharing economy

Access economysharingsharing economies
Sharing economy is a term for a way of distributing goods and services, a way that differs from the traditional model of corporations hiring employees and selling products to consumers. In the sharing economy, individuals are said to rent or "share" things like their cars, homes and personal time to other individuals in a peer-to-peer fashion.


Litecoin (LTC or Ł) is a peer-to-peer cryptocurrency and open-source software project released under the MIT/X11 license. Creation and transfer of coins is based on an open source cryptographic protocol and is not managed by any central authority. Litecoin was an early bitcoin spinoff or altcoin, starting in October 2011. In technical details, litecoin is nearly identical to Bitcoin. Litecoin was released via an open-source client on GitHub on October 7, 2011 by Charlie Lee, a Google employee and former Engineering Director at Coinbase. The Litecoin network went live on October 13, 2011.

Counterparty (platform)

CounterpartyCounterparty (technology)
Counterparty is a peer-to-peer financial platform and distributed, open source Internet protocol built on top of the Bitcoin blockchain and network. It was one of the most well-known "Bitcoin 2.0" platforms in 2014, along with Mastercoin, Ethereum, Colored Coins, Ripple and BitShares. It is a "metacoin"-type protocol, like Mastercoin and Colored Coins. It provides such features as tradable user-created currencies, additional financial instruments and a decentralized asset exchange.

Decentralized application

decentralizedDistributed Apps (DApps)
A decentralized application (DApp, dApp, Dapp, or dapp) is a computer application that runs on a distributed computing system. DApps have been popularized by distributed ledger technologies (DLT) such as the Ethereum Blockchain, where DApps are often referred to as smart contracts. DApps may run on top of distributed computing systems such as Ethereum or Bitcoin. Decentralized applications are stored on and executed by a blockchain system. *Cryptokitties - Game based on the Ethereum.

Ethereum Classic

Ethereum Classic is an open-source, public, blockchain-based distributed computing platform featuring smart contract (scripting) functionality. It provides a decentralized Turing-complete virtual machine, the Ethereum Virtual Machine (EVM), which can execute scripts using an international network of public nodes. Ethereum Classic and Ethereum have a value token called "ether", which can be transferred between participants, stored in a cryptocurrency wallet and is used to compensate participant nodes for computations performed in the Ethereum Platform. The classic ether token is traded on cryptocurrency exchanges under the ticker symbol ETC.

List of cryptocurrencies

List of scrypt crypto currenciesSHA-256 crypto currencies
By market capitalization, Bitcoin is currently (December 15, 2018) the largest blockchain network, followed by Ripple, Ethereum and Tether. As of 15 December 2018, total cryptocurrencies market capitalization is $100bn and larger than GDP of 127 countries. Below are some notable cryptocurrencies: *List of digital currencies