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]
Bitcoin is a digital currency, sometimes referred to as a cryptocurrency, best known as the world's first truly decentralized digital currency. Bitcoin is traded on a peer-to-peer basis with a distributed ledger called the Blockchain, and the Bitcoin exchange rate to the US Dollar and other major currencies is determined by supply and demand as with other global exchange rates. The traded value of Bitcoin has proven volatile through various booms and busts in demand. Ultimately, however, many see Bitcoin as a store of value against government-backed fiat currencies.

طرح شخص أطلق على نفسه الاسم الرمزي ساتوشي ناكاموتو فكرة بيتكوين للمرة الأولى في ورقة بحثية في عام 2008،[2] ووصفها بأنها نظام نقدي إلكتروني يعتمد في التعاملات المالية على مبدأ الند للند (بالإنجليزية: Peer-to-Peer) ، وهو مصطلح تقني يعني التعامل المباشر بين مستخدم وآخر دون وجود وسيط (كالتورنت). يقول القائمون على بيتكوين إن الهدف من هذه العملة التي طرحت للتداول للمرة الأولى سنة 2009 [3] هو تغيير الاقتصاد العالمي بنفس الطريقة التي غيرت بها الويب أساليب النشر.[4] وفي عام 2016 أعلن رجل الأعمال الأسترالي كريغ رايت أنه هو ساتوشي ناكاموتو مقدما دليلا تقنيا على ذلك ولكن تم كشف زيف أدلّته بسهولة.[5]
Full clients verify transactions directly by downloading a full copy of the blockchain (over 150 GB As of January 2018).[95] They are the most secure and reliable way of using the network, as trust in external parties is not required. Full clients check the validity of mined blocks, preventing them from transacting on a chain that breaks or alters network rules.[7]:ch. 1 Because of its size and complexity, downloading and verifying the entire blockchain is not suitable for all computing devices.

On 3 January 2009, the bitcoin network was created when Nakamoto mined the first block of the chain, known as the genesis block.[21][22] Embedded in the coinbase of this block was the text "The Times 03/Jan/2009 Chancellor on brink of second bailout for banks".[11] This note references a headline published by The Times and has been interpreted as both a timestamp and a comment on the instability caused by fractional-reserve banking.[23]:18


Ethereum was officially with an unusually long list of founders. Anthony Di Iorio wrote "Ethereum was founded by Vitalik Buterin, Myself, Charles Hoskinson, Mihai Alisie, & Amir Chetrit (the initial 5) in December 2013. Joseph Lubin, Gavin Wood, & Jeffrey Wilke were added in early 2014 as founders." Formal development of the Ethereum software project began in early 2014 through a Swiss company, Ethereum Switzerland GmbH (EthSuisse).[13][14] The basic idea of putting executable smart contracts in the blockchain needed to be specified before the software could be implemented; this work was done by Gavin Wood, then chief technology officer, in the Ethereum Yellow Paper that specified the Ethereum Virtual Machine.[15] Subsequently, a Swiss non-profit foundation, the Ethereum Foundation (Stiftung Ethereum), was created as well. Development was funded by an online public crowdsale during July–August 2014, with the participants buying the Ethereum value token (ether) with another digital currency, bitcoin.

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.
The "Metropolis Part 1: Byzantium" soft[citation needed] fork took effect on 16 October 2017, and included changes to reduce the complexity of the EVM and provide more flexibility for smart contract developers. Byzantium also added supports for zk-SNARKs (from Zcash), with the first zk-SNARK transaction occurring on testnet on September 19, 2017.[citation needed]

J. P. Morgan Chase is developing JPM Coin on a permissioned-variant of Ethereum blockchain dubbed "Quorum".[53] It's designed to toe the line between private and public in the realm of shuffling derivatives and payments. The idea is to satisfy regulators who need seamless access to financial goings-on, while protecting the privacy of parties that don't wish to reveal their identities nor the details of their transactions to the general public.[54]
On 1 August 2017, a hard fork of bitcoin was created, known as Bitcoin Cash.[111] Bitcoin Cash has a larger block size limit and had an identical blockchain at the time of fork. On 24 October 2017 another hard fork, Bitcoin Gold, was created. Bitcoin Gold changes the proof-of-work algorithm used in mining, as the developers felt that mining had become too specialized.[112]

Until relatively recently, building blockchain applications has required a complex background in coding, cryptography, mathematics as well as significant resources. But times have changed. Previously unimagined applications, from electronic voting & digitally recorded property assets to regulatory compliance & trading are now actively being developed and deployed faster than ever before. By providing developers with the tools to build decentralized applications, Ethereum is making all of this possible.


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]
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 ..
On 1 August 2017, a hard fork of bitcoin was created, known as Bitcoin Cash.[111] Bitcoin Cash has a larger block size limit and had an identical blockchain at the time of fork. On 24 October 2017 another hard fork, Bitcoin Gold, was created. Bitcoin Gold changes the proof-of-work algorithm used in mining, as the developers felt that mining had become too specialized.[112]
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]
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