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] 

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.
مقارنة بأجزاء أخرى من العالم بدأت الدول العربية في وقت متأخر نسبيا باستخدام بيتكوين حيث أعلن عن قبول هذه العملة لأول مرة في الأردن في بار شاي في العاصمة عمان. وتلى ذلك مطعم بيتزا وصراف آلي في دبي[15] ومن ثم شركة انظمه معلومات في فلسطين[16] كما أصبح سوق السفير من أوئل الاسواق في الكويت و الشرق الأوسط التي تقبل البتكوين في تعاملته [17]. اما بالنسبة للعملة الالكترونية في المشهد الاعلامي العربي فقد بدأت مؤخرا فقرات اخبارية تتحدث عنها ولو بشكل طفيف كما بدأت مواقع متخصصة في اخبار بيتكوين مثل موقع بيتكوين نيوز عربية [18] التابع لمجموعة اعلامية كبيرة،وعلى مستوى الشبكات الاجتماعية يمكن للمستخدمين في الشرق الأوسط وشمال افريقيا التفاعل على موقع askbitcoiner [19] الذي يعتبر أول شبكة اجتماعية للعملة الرقمية في العالم العربي حيث يمكن العثور على الاجوبة للاستفسارات حول العملة الرقمية وتقنية البلوك شاين. وعلى صعيد الشركات اللي توفر خدمات للبيتكون بالوطن العربي فمنهما يلو (بالإنجليزية: Yellow) و بت اويسس (بالإنجليزية: BitOasis) المؤسستان في دبي. بالإضافة إلى بت فلس (بالإنجليزية: BitFils) المؤسسة في الكويت. ويمكن شراء وتداول البيتكوين محليا عن طريق localbitcoins.com .
Several news outlets have asserted that the popularity of bitcoins hinges on the ability to use them to purchase illegal goods.[135][222] Nobel-prize winning economist Joseph Stiglitz says that bitcoin's anonymity encourages money laundering and other crimes, "If you open up a hole like bitcoin, then all the nefarious activity will go through that hole, and no government can allow that." He's also said that if "you regulate it so you couldn't engage in money laundering and all these other [crimes], there will be no demand for Bitcoin. By regulating the abuses, you are going to regulate it out of existence. It exists because of the abuses."[223][224]
Like Bitcoin, Ethereum is a distributed public blockchain network. Although there are some significant technical differences between the two, the most important distinction to note is that Bitcoin and Ethereum differ substantially in purpose and capability. Bitcoin offers one particular application of blockchain technology, a peer to peer electronic cash system that enables online Bitcoin payments. While the Bitcoin blockchain is used to track ownership of digital currency (bitcoins), the Ethereum blockchain focuses on running the programming code of any decentralized application.
A wallet stores the information necessary to transact bitcoins. While wallets are often described as a place to hold[93] or store bitcoins, due to the nature of the system, bitcoins are inseparable from the blockchain transaction ledger. A wallet is more correctly defined as something that "stores the digital credentials for your bitcoin holdings" and allows one to access (and spend) them.[7]:ch. 1, glossary Bitcoin uses public-key cryptography, in which two cryptographic keys, one public and one private, are generated.[94] At its most basic, a wallet is a collection of these keys.
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]
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.
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]
Network nodes can validate transactions, add them to their copy of the ledger, and then broadcast these ledger additions to other nodes. To achieve independent verification of the chain of ownership each network node stores its own copy of the blockchain.[76] About every 10 minutes, a new group of accepted transactions, called a block, is created, added to the blockchain, and quickly published to all nodes, without requiring central oversight. This allows bitcoin software to determine when a particular bitcoin was spent, which is needed to prevent double-spending. A conventional ledger records the transfers of actual bills or promissory notes that exist apart from it, but the blockchain is the only place that bitcoins can be said to exist in the form of unspent outputs of transactions.[7]:ch. 5
In 2014, researchers at the University of Kentucky found "robust evidence that computer programming enthusiasts and illegal activity drive interest in bitcoin, and find limited or no support for political and investment motives".[134] Australian researchers have estimated that 25% of all bitcoin users and 44% of all bitcoin transactions are associated with illegal activity as of April 2017. There were an estimated 24 million bitcoin users primarily using bitcoin for illegal activity. They held $8 billion worth of bitcoin, and made 36 million transactions valued at $72 billion.[225][226]
Ethereum’s core innovation, the Ethereum Virtual Machine (EVM) is a Turing complete software that runs on the Ethereum network. It enables anyone to run any program, regardless of the programming language given enough time and memory. The Ethereum Virtual Machine makes the process of creating blockchain applications much easier and efficient than ever before. Instead of having to build an entirely original blockchain for each new application, Ethereum enables the development of potentially thousands of different applications all on one platform. 

Leveraged trading in foreign currency or off-exchange products on margin carries significant risk and may not be suitable for all investors. We advise you to carefully consider whether trading is appropriate for you based on your personal circumstances. Forex trading involves risk. Losses can exceed deposits. We recommend that you seek independent advice and ensure you fully understand the risks involved before trading.
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]
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 ..
Physical wallets store the credentials necessary to spend bitcoins offline and can be as simple as a paper printout of the private key;[7]:ch. 10 a paper wallet. A paper wallet is created with a keypair generated on a computer with no internet connection; the private key is written or printed onto the paper[g] and then erased from the computer. The paper wallet can then be stored in a safe physical location for later retrieval. Bitcoins stored using a paper wallet are said to be in cold storage.[99]:39 In a 2014 interview, QuadrigaCX founder Gerald Cotten explained that the company stored customer funds on paper wallets in safe deposit boxes: "So we just send money to them, we don’t need to go back to the bank every time we want to put money into it. We just send money from our Bitcoin app directly to those paper wallets, and keep it safe that way."[100]
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.
In Charles Stross' 2013 science fiction novel, Neptune's Brood, the universal interstellar payment system is known as "bitcoin" and operates using cryptography.[227] Stross later blogged that the reference was intentional, saying "I wrote Neptune's Brood in 2011. Bitcoin was obscure back then, and I figured had just enough name recognition to be a useful term for an interstellar currency: it'd clue people in that it was a networked digital currency."[228]
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]
^ "Crib Sheet: Neptune's Brood – Charlie's Diary". www.antipope.org. Archived from the original on 14 June 2017. Retrieved 5 December 2017. I wrote Neptune's Brood in 2011. Bitcoin was obscure back then, and I figured had just enough name recognition to be a useful term for an interstellar currency: it'd clue people in that it was a networked digital currency.
Cameron and Tyler Winklevoss, the founders of the Gemini Trust Co. exchange, reported that they had cut their paper wallets into pieces and stored them in envelopes distributed to safe deposit boxes across the United States.[101] Through this system, the theft of one envelope would neither allow the thief to steal any bitcoins nor deprive the rightful owners of their access to them.[100]
A demo account is intended to familiarize you with the tools and features of our trading platforms and to facilitate the testing of trading strategies in a risk-free environment. Results achieved on the demo account are hypothetical and no representation is made that any account will or is likely to achieve actual profits or losses similar to those achieved in the demo account. Conditions in the demo account cannot always reasonably reflect all of the market conditions that may affect pricing and execution in a live trading environment.
• 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.
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