The successful miner finding the new block is allowed by the rest of the network to reward themselves with newly created bitcoins and transaction fees.[88] As of 9 July 2016,[89] the reward amounted to 12.5 newly created bitcoins per block added to the blockchain, plus any transaction fees from payments processed by the block. To claim the reward, a special transaction called a coinbase is included with the processed payments.[7]:ch. 8 All bitcoins in existence have been created in such coinbase transactions. The bitcoin protocol specifies that the reward for adding a block will be halved every 210,000 blocks (approximately every four years). Eventually, the reward will decrease to zero, and the limit of 21 million bitcoins[f] will be reached c. 2140; the record keeping will then be rewarded solely by transaction fees.[90]
Because of bitcoin's decentralized nature and its trading on online exchanges located in many countries, regulation of bitcoin has been difficult. However, the use of bitcoin can be criminalized, and shutting down exchanges and the peer-to-peer economy in a given country would constitute a de facto ban.[167] The legal status of bitcoin varies substantially from country to country and is still undefined or changing in many of them. Regulations and bans that apply to bitcoin probably extend to similar cryptocurrency systems.[168]
Transactions are defined using a Forth-like scripting language.[7]:ch. 5 Transactions consist of one or more inputs and one or more outputs. When a user sends bitcoins, the user designates each address and the amount of bitcoin being sent to that address in an output. To prevent double spending, each input must refer to a previous unspent output in the blockchain.[77] The use of multiple inputs corresponds to the use of multiple coins in a cash transaction. Since transactions can have multiple outputs, users can send bitcoins to multiple recipients in one transaction. As in a cash transaction, the sum of inputs (coins used to pay) can exceed the intended sum of payments. In such a case, an additional output is used, returning the change back to the payer.[77] Any input satoshis not accounted for in the transaction outputs become the transaction fee.[77]
The domain name "bitcoin.org" was registered on 18 August 2008.[17] On 31 October 2008, a link to a paper authored by Satoshi Nakamoto titled Bitcoin: A Peer-to-Peer Electronic Cash System[4] was posted to a cryptography mailing list.[18] Nakamoto implemented the bitcoin software as open-source code and released it in January 2009.[19][20][11] Nakamoto's identity remains unknown.[10]
An official investigation into bitcoin traders was reported in May 2018.[177] The U.S. Justice Department launched an investigation into possible price manipulation, including the techniques of spoofing and wash trades.[178][179][180] Traders in the U.S., the U.K, South Korea, and possibly other countries are being investigated.[177] Brett Redfearn, head of the U.S. Securities and Exchange Commission's Division of Trading and Markets, had identified several manipulation techniques of concern in March 2018.
Third-party internet services called online wallets offer similar functionality but may be easier to use. In this case, credentials to access funds are stored with the online wallet provider rather than on the user's hardware.[97] As a result, the user must have complete trust in the online wallet provider. A malicious provider or a breach in server security may cause entrusted bitcoins to be stolen. An example of such a security breach occurred with Mt. Gox in 2011.[98]
As with other cryptocurrencies, the validity of each ether is provided by a blockchain, which is a continuously growing list of records, called blocks, which are linked and secured using cryptography.[30][31] By design, the blockchain is inherently resistant to modification of the data. It is an open, distributed ledger that records transactions between two parties efficiently and in a verifiable and permanent way.[32] Unlike Bitcoin, Ethereum operates using accounts and balances in a manner called state transitions. This does not rely upon unspent transaction outputs (UTXOs). State denotes the current balances of all accounts and extra data. State is not stored on the blockchain, it is stored in a separate Merkle Patricia tree. A cryptocurrency wallet stores the public and private "keys" or "addresses" which can be used to receive or spend ether. These can be generated through BIP 39 style mnemonics for a BIP 32 "HD Wallet". In Ethereum, this is unnecessary as it does not operate in a UTXO scheme. With the private key, it is possible to write in the blockchain, effectively making an ether transaction.
Every 2,016 blocks (approximately 14 days at roughly 10 min per block), the difficulty target is adjusted based on the network's recent performance, with the aim of keeping the average time between new blocks at ten minutes. In this way the system automatically adapts to the total amount of mining power on the network.[7]:ch. 8 Between 1 March 2014 and 1 March 2015, the average number of nonces miners had to try before creating a new block increased from 16.4 quintillion to 200.5 quintillion.[86]
• الطبيعة الإنكماشية لعُملات البيتكوين: كما ذُكر أيضاُ عبر موقع الفتاوى  أن عُملات البيتكوين مثلها مثل أى عُملة آخرى لها طبيعة إنكماشية. نقصد بالطبيعة الإنكماشية هو التذبذب في الأسعار ما بين إرتفاع للقيمة السعرية وإنخفاض للقيمة السعرية بُناء على الحالة الإقتصادية العالمية ومدى إقبال الجمهور المُتعامل معها على شراء أو بيع العُملة. وهذا يدل على مصداقية العُملة وخضوعها لتغيرات السوق والعُملاء مثلها مثل سوق الذهب بالضبط.
The price of bitcoins has gone through cycles of appreciation and depreciation referred to by some as bubbles and busts.[159] In 2011, the value of one bitcoin rapidly rose from about US$0.30 to US$32 before returning to US$2.[160] In the latter half of 2012 and during the 2012–13 Cypriot financial crisis, the bitcoin price began to rise,[161] reaching a high of US$266 on 10 April 2013, before crashing to around US$50. On 29 November 2013, the cost of one bitcoin rose to a peak of US$1,242.[162] In 2014, the price fell sharply, and as of April remained depressed at little more than half 2013 prices. As of August 2014 it was under US$600.[163] During their time as bitcoin developers, Gavin Andresen[164] and Mike Hearn[165] warned that bubbles may occur.
Mining is a record-keeping service done through the use of computer processing power.[e] Miners keep the blockchain consistent, complete, and unalterable by repeatedly grouping newly broadcast transactions into a block, which is then broadcast to the network and verified by recipient nodes.[75] Each block contains a SHA-256 cryptographic hash of the previous block,[75] thus linking it to the previous block and giving the blockchain its name.[7]:ch. 7[75]
بروتوكول التوجيه بين البوابات (BGP)   بروتوكول التهيئة الآليّة للمضيفين (DHCP) بروتوكول التطبيقات المقيدة (CoAP) نظام أسماء النطاقات (DNS) بروتوكول نقل النصّ الفائق (HTTP) بروتوكول الوصول إلى رسائل الإنترنت (IMAP) بروتوكول النفاذ إلى الدليل البسيط (LDAP) برتوكول نقل أخبار الشبكة (NNTP) بروتوكول التوقيت في الشبكة (NTP) بروتوكول مكتب البريد (POP) بروتوكول معلومات التوجيه (RIP) بروتوكول التدفق في الزمن حقيقي (RTSP) بروتوكول وصف الجلسة (SDP) بروتوكول بدء جلسة (SIP) بروتوكول نقل الملفات (FTP) بروتوكول نقل الملفات البسيط (TFTP) بروتوكول إرسال البريد البسيط (SMTP) بروتوكول إدارة الشبكات البسيط (SNMP) بروتوكول الاتصال الآمن (SSH) بروتوكول تل نت (Telnet) سبيدي (SPDY) مزيد ..
As with other cryptocurrencies, the validity of each ether is provided by a blockchain, which is a continuously growing list of records, called blocks, which are linked and secured using cryptography.[30][31] By design, the blockchain is inherently resistant to modification of the data. It is an open, distributed ledger that records transactions between two parties efficiently and in a verifiable and permanent way.[32] Unlike Bitcoin, Ethereum operates using accounts and balances in a manner called state transitions. This does not rely upon unspent transaction outputs (UTXOs). State denotes the current balances of all accounts and extra data. State is not stored on the blockchain, it is stored in a separate Merkle Patricia tree. A cryptocurrency wallet stores the public and private "keys" or "addresses" which can be used to receive or spend ether. These can be generated through BIP 39 style mnemonics for a BIP 32 "HD Wallet". In Ethereum, this is unnecessary as it does not operate in a UTXO scheme. With the private key, it is possible to write in the blockchain, effectively making an ether transaction.
The Bank for International Settlements summarized several criticisms of bitcoin in Chapter V of their 2018 annual report. The criticisms include the lack of stability in bitcoin's price, the high energy consumption, high and variable transactions costs, the poor security and fraud at cryptocurrency exchanges, vulnerability to debasement (from forking), and the influence of miners.[189][190][191]
Ethereum was proposed in late 2013 by Vitalik Buterin, a cryptocurrency researcher and programmer. Development was funded by an online crowdsale that took place between July and August 2014.[4] The system then went live on 30 July 2015, with 72 million coins "premined". This accounts for about 68 percent of the total circulating supply in 2019. [5]

حاليا لا يُملك مالكو عملات بيتكوين خيارات كثيرة لإنفاق أموالهم من خلالها، وهو ما يدفع ببعضهم إلى استبدالها مقابل العملات التقليدية. يتم ذلك عادة عبر منصات خاصة بذلك حيث يتم استبدال البيتكوينات مع مُستخدمين آخرين لها. يبدو أنه وفي حال ما إذا رغبت الحكومات في معرفة هويات أصحاب بعض الحسابات فما عليها سوى أن تقوم بتقنين عمليات التحويل بدل منعها، حيث سيصبح بالإمكان معرفة اسم صاحب كل حساب بُمجرد أن يرغب في استبدال ما بحوزته مقابل عملات تقليدية، وهو ما يُمثل نقطة انطلاق لتتبع الأموال المسروقة.


^ Iansiti, Marco; Lakhani, Karim R. (January 2017). "The Truth About Blockchain". Harvard Business Review. Harvard University. 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.

• غطاء تمويلى للمنظمات الإرهابية: قامت دار الإفتاء المصرية بتصريح أن عمليات الإستثمار والتداول في البيتكوين تُعتبر عمليات مُحرمة من قبل الدين والشرع حيث إنها تعمل كغطاء لتمويل المنظمات الإرهابية وعصابات المُخدرات. كما لعدم وجود هيئات حكومية وبنوك مركزية كان لذلك آثر رهيب على استخدام إستثمارات البيتكوين في عمليات غسيل الأموال والتى بالطبع نهانا الرسول عنها، بل ويُحاسب عليها القانون أيضاً.

الجدير بالذكر بأن بعض المواقع كانت تنشر سابقا تقديرا لمقدار الخسارة/ الربح الذي يُسجله المنقبون لكن يبدو بأنهم توقفوا عن القيام بذلك لأسباب نجهلها. قد يعتقد البعض بأنه لم يكن بالإمكان إعطاء تقدير دقيق لمقدار الخسارة أو الربح الذي يُسجله المنقبون، ولذلك تم التخلص من ذلك. إلا أنه من المُمكن جدا أنه تم التخلص من ذلك لكيلا يتم تنفير المُنقبين من عمليات التنقيب.
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 crowdsale to fund the project.[25] The DAO was exploited in June when US$50 million in ether were taken by an unknown hacker.[26][27] The event sparked a debate in the crypto-community about whether Ethereum should perform a contentious "hard fork" to reappropriate the affected funds.[28] As a result of the dispute, the network split in two. Ethereum (the subject of this article) continued on the forked blockchain, while Ethereum Classic continued on the original blockchain.[29] The hard fork created a rivalry between the two networks.
Ether is a token whose blockchain is generated by the Ethereum platform. Ether can be transferred between accounts and used to compensate participant mining nodes for computations performed.[3] Ethereum provides a decentralized virtual machine, the Ethereum Virtual Machine (EVM), which can execute scripts using an international network of public nodes.[4] The virtual machine's instruction set, in contrast to others like Bitcoin Script, is thought to be Turing-complete. "Gas", an internal transaction pricing mechanism, is used to mitigate spam and allocate resources on the network.[4]
To be accepted by the rest of the network, a new block must contain a proof-of-work (PoW).[75] The system used is based on Adam Back's 1997 anti-spam scheme, Hashcash.[85][4] The PoW requires miners to find a number called a nonce, such that when the block content is hashed along with the nonce, the result is numerically smaller than the network's difficulty target.[7]:ch. 8 This proof is easy for any node in the network to verify, but extremely time-consuming to generate, as for a secure cryptographic hash, miners must try many different nonce values (usually the sequence of tested values is the ascending natural numbers: 0, 1, 2, 3, ...[7]:ch. 8) before meeting the difficulty target.

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The rapid price increase of Ethereum has not only attracted investors but developers too. Ethereum has tens of thousands of developers in its open source community, each contributing to the many layers of the “Ethereum stack”. This includes code contributions to the core Ethereum clients, second layer scaling tech and the “decentralized applications” (dApps) that are built on top of the platform. The appeal of Ethereum to developers is unique in that it was the first platform to allow anyone in the world to write and deploy code that would run without the risk of censorship. The community of developers which have formed around these core principles have led to the creation of technologies that could not have existed without the inception of Ethereum, many of which were never predicted. Some of the major use-cases of Ethereum so far have been:
Ether is a token whose blockchain is generated by the Ethereum platform. Ether can be transferred between accounts and used to compensate participant mining nodes for computations performed.[3] Ethereum provides a decentralized virtual machine, the Ethereum Virtual Machine (EVM), which can execute scripts using an international network of public nodes.[4] The virtual machine's instruction set, in contrast to others like Bitcoin Script, is thought to be Turing-complete. "Gas", an internal transaction pricing mechanism, is used to mitigate spam and allocate resources on the network.[4]
Despite the fallout from The DAO hack, Ethereum is moving forward and looking to a bright future. By providing a user-friendly platform that enables people to harness the power of blockchain technology, Ethereum is speeding up the decentralization of the world economy. Decentralized applications have the potential to profoundly disrupt hundreds of industries including finance, real estate, academia, insurance, healthcare and the public sector amongst many others.

The proof-of-work system, alongside the chaining of blocks, makes modifications of the blockchain extremely hard, as an attacker must modify all subsequent blocks in order for the modifications of one block to be accepted.[87] As new blocks are mined all the time, the difficulty of modifying a block increases as time passes and the number of subsequent blocks (also called confirmations of the given block) increases.[75]
Ethereum was announced at the North American Bitcoin Conference in Miami, in January, 2014.[9] During the same time as the conference, a group of people rented a house in Miami Gavin Wood, Charles Hoskinson, and Anthony Di Iorio, a Torontonian who financed the project.[9] Di Iorio invited friend Joseph Lubin, who invited reporter Morgen Peck, to bear witness.[9] Six months later the founders met again in a house in Zug Switzerland, where Buterin told the founders that the project would proceed as a non-profit. Hoskinson left the project at that time.[9]
^ Mooney, Chris; Mufson, Steven (19 December 2017). "Why the bitcoin craze is using up so much energy". The Washington Post. Archived from the original on 9 January 2018. Retrieved 11 January 2018. several experts told The Washington Post that bitcoin probably uses as much as 1 to 4 gigawatts, or billion watts, of electricity, roughly the output of one to three nuclear reactors.
Venture capitalists, such as Peter Thiel's Founders Fund, which invested US$3 million in BitPay, do not purchase bitcoins themselves, but instead fund bitcoin infrastructure that provides payment systems to merchants, exchanges, wallet services, etc.[154] In 2012, an incubator for bitcoin-focused start-ups was founded by Adam Draper, with financing help from his father, venture capitalist Tim Draper, one of the largest bitcoin holders after winning an auction of 30,000 bitcoins,[155] at the time called "mystery buyer".[156] The company's goal is to fund 100 bitcoin businesses within 2–3 years with $10,000 to $20,000 for a 6% stake.[155] Investors also invest in bitcoin mining.[157] According to a 2015 study by Paolo Tasca, bitcoin startups raised almost $1 billion in three years (Q1 2012 – Q1 2015).[158]
Ethereum has recently created a new standard called the ERC721 token for tracking unique digital assets. One of the biggest use cases currently for such tokens is digital collectibles, as the infrastructure allows for people to prove ownership of scarce digital goods. Many games are currently being built using this technology, such as the overnight hit CryptoKitties, a game where you can collect and breed digital cats.
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