According to The New York Times, libertarians and anarchists were attracted to the idea. Early bitcoin supporter Roger Ver said: "At first, almost everyone who got involved did so for philosophical reasons. We saw bitcoin as a great idea, as a way to separate money from the state."[126] The Economist describes bitcoin as "a techno-anarchist project to create an online version of cash, a way for people to transact without the possibility of interference from malicious governments or banks".[129]
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]

Researchers have pointed out at a "trend towards centralization". Although bitcoin can be sent directly from user to user, in practice intermediaries are widely used.[32]:220–222 Bitcoin miners join large mining pools to minimize the variance of their income.[32]:215, 219–222[115]:3[116] Because transactions on the network are confirmed by miners, decentralization of the network requires that no single miner or mining pool obtains 51% of the hashing power, which would allow them to double-spend coins, prevent certain transactions from being verified and prevent other miners from earning income.[117] As of 2013 just six mining pools controlled 75% of overall bitcoin hashing power.[117] In 2014 mining pool Ghash.io obtained 51% hashing power which raised significant controversies about the safety of the network. The pool has voluntarily capped their hashing power at 39.99% and requested other pools to act responsibly for the benefit of the whole network.[118] Between 2017 and 2019 over 70% of the hashing power and 90% of transactions were operating from China.[119]
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.
تُعتبر بيتكوين عُملة معمّاة (بالإنجليزية: cryptocurrency) ويُقصد بذلك أنها تعتمد بشكل أساسي على مبادئ التشفير في جميع جوانبها، كما أنها تُعتبر أيضا العُملة الأولى من نوعها والأكثر شهرة وانتشارًا لكن رغم ذلك ليست العُملة التشفيرية الوحيدة الموجودة على شبكة الإنترنت حاليًا. حيث يتوفر ما يزيد عن 60 عُملة تشفيرية مُختلفة[6] منها 6 عُملات يُمكن وصفها بالرئيسية [7] وذلك اعتمادًا على عدد المُستخدمين وبنية كل شبكة، إضافة إلى الأماكن التي يُمكن استبدال وشراء هذه العُملات التشفيرية مُقابل عُملات أخرى. جميع العُملات التشفيرية الحالية مبنية على مبدأ عمل عُملة بيتكوين نفسها باستثناء عُملة Ripple [8]، وبما أن عُملة بيتكوين مفتوحة المصدر فإنه من المُمكن استنساخها وإدخال بعض التعديلات عليها ومن ثم إطلاق عُملة جديدة.
Ethereum's blockchain uses Merkle trees, for security reasons, to improve scalability, and to optimize transaction hashing.[61] As with any Merkle tree implementation, it allows for storage savings, set membership proofs (called "Merkle proofs"), and light client synchronization. The Ethereum network has at times faced congestion problems, for example, congestion occurred during late 2017 in relation to Cryptokitties.[62]
The receiver of the first bitcoin transaction was cypherpunk Hal Finney, who created the first reusable proof-of-work system (RPoW) in 2004.[24] Finney downloaded the bitcoin software on its release date, and on 12 January 2009 received ten bitcoins from Nakamoto.[25][26] Other early cypherpunk supporters were creators of bitcoin predecessors: Wei Dai, creator of b-money, and Nick Szabo, creator of bit gold.[21] In 2010, the first known commercial transaction using bitcoin occurred when programmer Laszlo Hanyecz bought two Papa John's pizzas for ₿10,000.[27]
Bitcoin is pseudonymous, meaning that funds are not tied to real-world entities but rather bitcoin addresses. Owners of bitcoin addresses are not explicitly identified, but all transactions on the blockchain are public. In addition, transactions can be linked to individuals and companies through "idioms of use" (e.g., transactions that spend coins from multiple inputs indicate that the inputs may have a common owner) and corroborating public transaction data with known information on owners of certain addresses.[120] Additionally, bitcoin exchanges, where bitcoins are traded for traditional currencies, may be required by law to collect personal information.[121] To heighten financial privacy, a new bitcoin address can be generated for each transaction.[122]

In March 2017, various blockchain start-ups, research groups, and Fortune 500 companies announced the creation of the Enterprise Ethereum Alliance (EEA) with 30 founding members.[16] By May, the nonprofit organization had 116 enterprise members—including ConsenSys, CME Group, Cornell University's research group, Toyota Research Institute, Samsung SDS, Microsoft, Intel, J. P. Morgan, Cooley LLP, Merck KGaA, DTCC, Deloitte, Accenture, Banco Santander, BNY Mellon, ING, and National Bank of Canada.[17][18][19] By July 2017, there were over 150 members in the alliance, including recent additions MasterCard, Cisco Systems, Sberbank and Scotiabank.[20][21]

EthereumPrice.org was developed by Ether0x in March 2016 to allow users to easily track the price of Ethereum both historically and in real-time. The platform has since evolved to include several fiat currencies (EUR, GBP, JPY and others) as well as price data for a number of Ethereum ERC20 tokens and other blockchain currencies. More recently, prediction data from Augur was also added to provide insight into the future price expectations of the Ether market. Price data is currently sourced from multiple exchanges with the weighted average price of these assets being calculated by CryptoCompare.com. For more details on the weighted average calculation, see our FAQ.


• لا حرج من دفع عمولات تحويل العملات: كما هو شائع بالنسبة للبعض أن دفع العُمولات عبر شبكات الإنترنت مقابل خدمات تحويل أو شراء عُملات البيتكوين يُعد شكل من أشكال الربا غير المسموح بها. لكن إستناداُ إلى ما تم ذكره بحسب الفتوى رقم 259576 أن لا هناك أى حرج على دفع مثل هذه العمولات. حيث إنك تدفع مُقابل حصولك على خدمة معينة بما فيها خدمات تحويل وشراء عُملات البيتكوين الإفتراضية.

من منظور المنقبين فإن سعر البيتكوين الحالي أقل بكثير مما يجب عليه أن يكون، ولهذا ستجد أنه لا رغبة لديهم في بيع العُملات التي بحوزتهم بأسعار مُنخفضة لأنهم قد استخدموا كميات هائلة من الكهرباء لإنتاجها، إضافة إلى الاستثمار في عتاد خاص للقيام بذلك. الوضع سيزداد سوءا بالنسبة إليهم ما لم ينخفض عدد المُنقبين بشكل مُعتبر، حيث أن عدد العُملات التي سيتم إنتاجها ستنخفض إلى النصف كل 4 سنوات. في المقابل، تم إنتاج كميات كبيرة من البيتكوينات بشكل رخيص جدا في بدايات العُملة لما كان عدد المُنقبين قليلا ولما كان عامل “الصعوبة” hardness منخفضا جدا، وبالتالي حاجة إلى كهرباء أقل، هذا الأمر خلق حالة من اللاتوازن داخل شبكة العُملة، حيث بإمكان أصحاب البيتكوينات القديمة بيع عُملاتهم دون تسجيل خسائر مُقارنة بمن انضموا إلى جبهة المُنقبين مؤخرا.
To lower the costs, bitcoin miners have set up in places like Iceland where geothermal energy is cheap and cooling Arctic air is free.[205] Bitcoin miners are known to use hydroelectric power in Tibet, Quebec, Washington (state), and Austria to reduce electricity costs.[204][206] Miners are attracted to suppliers such as Hydro Quebec that have energy surpluses.[207] According to a University of Cambridge study, much of bitcoin mining is done in China, where electricity is subsidized by the government.[208][209]
In March 2013 the blockchain temporarily split into two independent chains with different rules due to a bug in version 0.8 of the bitcoin software. The two blockchains operated simultaneously for six hours, each with its own version of the transaction history from the moment of the split. Normal operation was restored when the majority of the network downgraded to version 0.7 of the bitcoin software, selecting the backward compatible version of the blockchain. As a result, this blockchain became the longest chain and could be accepted by all participants, regardless of their bitcoin software version.[38] During the split, the Mt. Gox exchange briefly halted bitcoin deposits and the price dropped by 23% to $37[38][39] before recovering to previous level of approximately $48 in the following hours.[40] The US Financial Crimes Enforcement Network (FinCEN) established regulatory guidelines for "decentralized virtual currencies" such as bitcoin, classifying American bitcoin miners who sell their generated bitcoins as Money Service Businesses (MSBs), that are subject to registration or other legal obligations.[41][42][43] In April, exchanges BitInstant and Mt. Gox experienced processing delays due to insufficient capacity[44] resulting in the bitcoin price dropping from $266 to $76 before returning to $160 within six hours.[45] The bitcoin price rose to $259 on 10 April, but then crashed by 83% to $45 over the next three days.[36] On 15 May 2013, US authorities seized accounts associated with Mt. Gox after discovering it had not registered as a money transmitter with FinCEN in the US.[46][47] On 23 June 2013, the US Drug Enforcement Administration listed ₿11.02 as a seized asset in a United States Department of Justice seizure notice pursuant to 21 U.S.C. § 881.[48][better source needed] This marked the first time a government agency had seized bitcoin.[49] The FBI seized about ₿30,000[50] in October 2013 from the dark web website Silk Road during the arrest of Ross William Ulbricht.[51][52][53] These bitcoins were sold at blind auction by the United States Marshals Service to venture capital investor Tim Draper.[50] Bitcoin's price rose to $755 on 19 November and crashed by 50% to $378 the same day. On 30 November 2013 the price reached $1,163 before starting a long-term crash, declining by 87% to $152 in January 2015.[36] On 5 December 2013, the People's Bank of China prohibited Chinese financial institutions from using bitcoins.[54] After the announcement, the value of bitcoins dropped,[55] and Baidu no longer accepted bitcoins for certain services.[56] Buying real-world goods with any virtual currency had been illegal in China since at least 2009.[57]
Ethereum blockchain applications are usually referred to as DApps (decentralized application), since they are based on the decentralized Ethereum Virtual Machine, and its smart contracts.[46] Many uses have been proposed for Ethereum platform, including ones that are impossible or unfeasible.[47][33] Use case proposals have included finance, the internet-of-things, farm-to-table produce, electricity sourcing and pricing, and sports betting. Ethereum is (as of 2017) the leading blockchain platform for initial coin offering projects, with over 50% market share.
Researchers have pointed out at a "trend towards centralization". Although bitcoin can be sent directly from user to user, in practice intermediaries are widely used.[32]:220–222 Bitcoin miners join large mining pools to minimize the variance of their income.[32]:215, 219–222[115]:3[116] Because transactions on the network are confirmed by miners, decentralization of the network requires that no single miner or mining pool obtains 51% of the hashing power, which would allow them to double-spend coins, prevent certain transactions from being verified and prevent other miners from earning income.[117] As of 2013 just six mining pools controlled 75% of overall bitcoin hashing power.[117] In 2014 mining pool Ghash.io obtained 51% hashing power which raised significant controversies about the safety of the network. The pool has voluntarily capped their hashing power at 39.99% and requested other pools to act responsibly for the benefit of the whole network.[118] Between 2017 and 2019 over 70% of the hashing power and 90% of transactions were operating from China.[119]

Ethereum is also being used as a platform to launch other cryptocurrencies. Because of the ERC20 token standard defined by the Ethereum Foundation, other developers can issue their own versions of this token and raise funds with an initial coin offering (ICO). In this fundraising strategy, the issuers of the token set an amount they want to raise, offer it in a crowdsale, and receive Ether in exchange. Billions of dollars have been raised by ICOs on the Ethereum platform in the last two years, and one of the most valuable cryptocurrencies in the world, EOS, is an ERC20 token.
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]
According to The New York Times, libertarians and anarchists were attracted to the idea. Early bitcoin supporter Roger Ver said: "At first, almost everyone who got involved did so for philosophical reasons. We saw bitcoin as a great idea, as a way to separate money from the state."[126] The Economist describes bitcoin as "a techno-anarchist project to create an online version of cash, a way for people to transact without the possibility of interference from malicious governments or banks".[129]

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]
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]
Bitcoin is a digital asset designed to work in peer-to-peer transactions as a currency.[4][135] Bitcoins have three qualities useful in a currency, according to The Economist in January 2015: they are "hard to earn, limited in supply and easy to verify."[136] Per some researchers, as of 2015, bitcoin functions more as a payment system than as a currency.[32]
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.
• 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.

^ Jump up to: a b c d e Joshua A. Kroll; Ian C. Davey; Edward W. Felten (11–12 June 2013). "The Economics of Bitcoin Mining, or Bitcoin in the Presence of Adversaries" (PDF). The Twelfth Workshop on the Economics of Information Security (WEIS 2013). Archived (PDF) from the original on 9 May 2016. Retrieved 26 April 2016. A transaction fee is like a tip or gratuity left for the miner.


In Ethereum all smart contracts are stored publicly on every node of the blockchain, which has costs.[57] Being a blockchain means it is secure by design and is an example of a distributed computing system with high Byzantine fault tolerance. The downside is that performance issues arise in that every node is calculating all the smart contracts in real time, resulting in lower speeds.[57] As of January 2016, the Ethereum protocol could process about 25 transactions per second.[57] In comparison, the Visa payment platform processes 45,000 payments per second leading some to question the scalability of Ethereum.[58] On 19 December 2016, Ethereum exceeded one million transactions in a single day for the first time.[59]

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.


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.
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.
Bitcoin is a digital asset designed to work in peer-to-peer transactions as a currency.[4][135] Bitcoins have three qualities useful in a currency, according to The Economist in January 2015: they are "hard to earn, limited in supply and easy to verify."[136] Per some researchers, as of 2015, bitcoin functions more as a payment system than as a currency.[32]
Various journalists,[205][210] economists,[211][212] and the central bank of Estonia[213] have voiced concerns that bitcoin is a Ponzi scheme. In April 2013, Eric Posner, a law professor at the University of Chicago, stated that "a real Ponzi scheme takes fraud; bitcoin, by contrast, seems more like a collective delusion."[214] A July 2014 report by the World Bank concluded that bitcoin was not a deliberate Ponzi scheme.[215]:7 In June 2014, the Swiss Federal Council[216]:21 examined the concerns that bitcoin might be a pyramid scheme; it concluded that, "Since in the case of bitcoin the typical promises of profits are lacking, it cannot be assumed that bitcoin is a pyramid scheme." In July 2017, billionaire Howard Marks referred to bitcoin as a pyramid scheme.[217]
^ 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.
According to the European Central Bank, the decentralization of money offered by bitcoin has its theoretical roots in the Austrian school of economics, especially with Friedrich von Hayek in his book Denationalisation of Money: The Argument Refined,[127] in which Hayek advocates a complete free market in the production, distribution and management of money to end the monopoly of central banks.[128]:22 

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.
^ Jump up to: a b c d "Statement of Jennifer Shasky Calvery, Director Financial Crimes Enforcement Network United States Department of the Treasury Before the United States Senate Committee on Banking, Housing, and Urban Affairs Subcommittee on National Security and International Trade and Finance Subcommittee on Economic Policy" (PDF). fincen.gov. Financial Crimes Enforcement Network. 19 November 2013. Archived (PDF) from the original on 9 October 2016. Retrieved 1 June 2014.
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.

Bloomberg reported that the largest 17 crypto merchant-processing services handled $69 million in June 2018, down from $411 million in September 2017. Bitcoin is "not actually usable" for retail transactions because of high costs and the inability to process chargebacks, according to Nicholas Weaver, a researcher quoted by Bloomberg. High price volatility and transaction fees make paying for small retail purchases with bitcoin impractical, according to economist Kim Grauer. However, bitcoin continues to be used for large-item purchases on sites such as Overstock.com, and for cross-border payments to freelancers and other vendors.[141]


EthereumPrice.org was developed by Ether0x in March 2016 to allow users to easily track the price of Ethereum both historically and in real-time. The platform has since evolved to include several fiat currencies (EUR, GBP, JPY and others) as well as price data for a number of Ethereum ERC20 tokens and other blockchain currencies. More recently, prediction data from Augur was also added to provide insight into the future price expectations of the Ether market. Price data is currently sourced from multiple exchanges with the weighted average price of these assets being calculated by CryptoCompare.com. For more details on the weighted average calculation, see our FAQ.
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