Bitcoin graphics card wikipedia
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. Paying a transaction fee is optional. Because the size of mined blocks is capped by the network, miners choose transactions based on the fee paid relative to their storage size, not the absolute amount of money paid as a fee.
The size of transactions is dependent on the number of inputs used to create the transaction, and the number of outputs. In the blockchain, bitcoins are registered to bitcoin addresses. Creating a bitcoin address is nothing more than picking a random valid private key and computing the corresponding bitcoin address. This computation can be done in a split second.
But the reverse computing the private key of a given bitcoin address is mathematically unfeasible and so users can tell others and make public a bitcoin address without compromising its corresponding private key. Moreover, the number of valid private keys is so vast that it is extremely unlikely someone will compute a key-pair that is already in use and has funds. The vast number of valid private keys makes it unfeasible that brute force could be used for that. To be able to spend the bitcoins, the owner must know the corresponding private key and digitally sign the transaction.
The network verifies the signature using the public key. If the private key is lost, the bitcoin network will not recognize any other evidence of ownership; [8] the coins are then unusable, and effectively lost. Mining is a record-keeping service done through the use of computer processing power.
To be accepted by the rest of the network, a new block must contain a so-called proof-of-work PoW. Every 2, 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. 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.
Computing power is often bundled together or "pooled" to reduce variance in miner income. Individual mining rigs often have to wait for long periods to confirm a block of transactions and receive payment. In a pool, all participating miners get paid every time a participating server solves a block.
This payment depends on the amount of work an individual miner contributed to help find that block. The successful miner finding the new block is rewarded with newly created bitcoins and transaction fees. To claim the reward, a special transaction called a coinbase is included with the processed payments.
The bitcoin protocol specifies that the reward for adding a block will be halved every , blocks approximately every four years. Eventually, the reward will decrease to zero, and the limit of 21 million bitcoins [f] will be reached c. Their numbers are being released roughly every ten minutes and the rate at which they are generated would drop by half every four years until all were in circulation. A wallet stores the information necessary to transact bitcoins.
While wallets are often described as a place to hold [59] or store bitcoins, [60] due to the nature of the system, bitcoins are inseparable from the blockchain transaction ledger. A better way to describe a wallet is something that "stores the digital credentials for your bitcoin holdings" [60] and allows one to access and spend them.
Bitcoin uses public-key cryptography , in which two cryptographic keys, one public and one private, are generated. There are three modes which wallets can operate in.
They have an inverse relationship with regards to trustlessness and computational requirements. 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. 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. Physical wallets store offline the credentials necessary to spend bitcoins. Another type of wallet called a hardware wallet keeps credentials offline while facilitating transactions. The first wallet program — simply named "Bitcoin" — was released in by Satoshi Nakamoto as open-source code. While a decentralized system cannot have an "official" implementation, Bitcoin Core is considered by some to be bitcoin's preferred implementation.
Bitcoin was designed not to need a central authority [5] and the bitcoin network is considered to be decentralized. In mining pool Ghash. The pool has voluntarily capped their hashing power at 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. To heighten financial privacy, a new bitcoin address can be generated for each transaction. Wallets and similar software technically handle all bitcoins as equivalent, establishing the basic level of fungibility.
Researchers have pointed out that the history of each bitcoin is registered and publicly available in the blockchain ledger, and that some users may refuse to accept bitcoins coming from controversial transactions, which would harm bitcoin's fungibility. The blocks in the blockchain were originally limited to 32 megabyte in size. The block size limit of one megabyte was introduced by Satoshi Nakamoto in , as an anti-spam measure. Transactions contain some data which is only used to verify the transaction, and does not otherwise effect the movement of coins.
SegWit introduces a new transaction format that moves this data into a new field in a backwards-compatible way. The segregated data, the so-called witness , is not sent to non-SegWit nodes and therefore does not form part of the blockchain as seen by legacy nodes. This lowers the size of the average transaction in such nodes' view, thereby increasing the block size without incurring the hard fork implied by other proposals for block size increases.
Bitcoin is a digital asset designed by its inventor, Satoshi Nakamoto, to work as a currency. The question whether bitcoin is a currency or not is still disputed. According to research produced by Cambridge University , there were between 2.
The number of users has grown significantly since , when there were , to 1. In , the number of merchants accepting bitcoin exceeded , Reasons for this fall include high transaction fees due to bitcoin's scalability issues, long transaction times and a rise in value making consumers unwilling to spend it.
Merchants accepting bitcoin ordinarily use the services of bitcoin payment service providers such as BitPay or Coinbase. When a customer pays in bitcoin, the payment service provider accepts the bitcoin on behalf of the merchant, converts it to the local currency, and sends the obtained amount to merchant's bank account, charging a fee for the service.
Bitcoins can be bought on digital currency exchanges. According to Tony Gallippi , a co-founder of BitPay , "banks are scared to deal with bitcoin companies, even if they really want to". In a report, Bank of America Merrill Lynch stated that "we believe bitcoin can become a major means of payment for e-commerce and may emerge as a serious competitor to traditional money-transfer providers. Plans were announced to include a bitcoin futures option on the Chicago Mercantile Exchange in Some Argentinians have bought bitcoins to protect their savings against high inflation or the possibility that governments could confiscate savings accounts.
The Winklevoss twins have invested into bitcoins. Other methods of investment are bitcoin funds. The first regulated bitcoin fund was established in Jersey in July and approved by the Jersey Financial Services Commission. Forbes named bitcoin the best investment of The price of bitcoins has gone through various cycles of appreciation and depreciation referred to by some as bubbles and busts. According to Mark T.
Various journalists, [78] [] economists, [] [] and the central bank of Estonia [] have voiced concerns that bitcoin is a Ponzi scheme. In , 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. Zero Hedge claimed that the same day Dimon made his statement, JP Morgan also purchased a large amount of bitcoins for its clients. You can have cryptodollars in yen and stuff like that.
Bitcoin has been labelled a speculative bubble by many including former Fed Chairman Alan Greenspan [] and economist John Quiggin. Lee, in a piece for The Washington Post pointed out that the observed cycles of appreciation and depreciation don't correspond to the definition of speculative bubble. It's a mirage, basically.
Because of bitcoin's decentralized nature, nation-states cannot shut down the network or alter its technical rules. While some countries have explicitly allowed its use and trade, others have banned or restricted it. Regulations and bans that apply to bitcoin probably extend to similar cryptocurrency systems.
Bitcoin has been criticized for the amounts of electricity consumed by mining. As of , The Economist estimated that even if all miners used modern facilities, the combined electricity consumption would be To lower the costs, bitcoin miners have set up in places like Iceland where geothermal energy is cheap and cooling Arctic air is free.
The use of bitcoin by criminals has attracted the attention of financial regulators, legislative bodies, law enforcement, and the media. Senate held a hearing on virtual currencies in November Several news outlets have asserted that the popularity of bitcoins hinges on the ability to use them to purchase illegal goods. It will cover studies of cryptocurrencies and related technologies, and is published by the University of Pittsburgh. Authors are also asked to include a personal bitcoin address in the first page of their papers.
The documentary film, The Rise and Rise of Bitcoin late , features interviews with people who use bitcoin, such as a computer programmer and a drug dealer. In Charles Stross ' science fiction novel, Neptune's Brood , "bitcoin" a modified version is used as the universal interstellar payment system. From Wikipedia, the free encyclopedia. For a broader coverage related to this topic, see Blockchain. For a broader coverage related to this topic, see Cryptocurrency wallet.
Legality of bitcoin by country or territory. Cryptography portal Business and economics portal Free and open-source software portal Internet portal Numismatics portal.
The timestamp of the block is This block is unlike all other blocks in that it doesn't have a previous block to reference. The fact is that gold miners are rewarded for producing gold, while bitcoin miners are not rewarded for producing bitcoins; they are rewarded for their record-keeping services. Archived from the original on 7 August Retrieved 25 May Archived from the original on 20 June Retrieved 20 June Archived from the original on 20 January Retrieved 30 September Archived PDF from the original on 20 March Retrieved 28 April Financial Crimes Enforcement Network.
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Is It Bitcoin, or bitcoin? The Orthography of the Cryptography". Archived from the original on 19 April Retrieved 21 April The Chronicle of Higher Education chronicle.
Archived from the original on 16 April Retrieved 19 April An " arms race " has been observed through the various hashing technologies that have been used to mine bitcoins: Computing power is often bundled together or "pooled" to reduce variance in miner income.
Individual mining rigs often have to wait for long periods to confirm a block of transactions and receive payment. In a pool, all participating miners get paid every time a participating server solves a block.
This payment depends on the amount of work an individual miner contributed to help find that block. Bitcoin data centers prefer to keep a low profile, are dispersed around the world and tend to cluster around the availability of cheap electricity.
In , Mark Gimein estimated electricity consumption to be about To lower the costs, bitcoin miners have set up in places like Iceland where geothermal energy is cheap and cooling Arctic air is free.
A rough overview of the process to mine bitcoins is: By convention, the first transaction in a block is a special transaction that produces new bitcoins owned by the creator of the block. This is the incentive for nodes to support the network. The reward for mining halves every , blocks. It started at 50 bitcoin, dropped to 25 in late and to Various potential attacks on the bitcoin network and its use as a payment system, real or theoretical, have been considered.
The bitcoin protocol includes several features that protect it against some of those attacks, such as unauthorized spending, double spending, forging bitcoins, and tampering with the blockchain. Other attacks, such as theft of private keys, require due care by users.
Unauthorized spending is mitigated by bitcoin's implementation of public-private key cryptography. For example; when Alice sends a bitcoin to Bob, Bob becomes the new owner of the bitcoin. Eve observing the transaction might want to spend the bitcoin Bob just received, but she cannot sign the transaction without the knowledge of Bob's private key. A specific problem that an internet payment system must solve is double-spending , whereby a user pays the same coin to two or more different recipients.
An example of such a problem would be if Eve sent a bitcoin to Alice and later sent the same bitcoin to Bob. The bitcoin network guards against double-spending by recording all bitcoin transfers in a ledger the blockchain that is visible to all users, and ensuring for all transferred bitcoins that they haven't been previously spent. If Eve offers to pay Alice a bitcoin in exchange for goods and signs a corresponding transaction, it is still possible that she also creates a different transaction at the same time sending the same bitcoin to Bob.
By the rules, the network accepts only one of the transactions. This is called a race attack , since there is a race which transaction will be accepted first. Alice can reduce the risk of race attack stipulating that she will not deliver the goods until Eve's payment to Alice appears in the blockchain.
A variant race attack which has been called a Finney attack by reference to Hal Finney requires the participation of a miner.
Instead of sending both payment requests to pay Bob and Alice with the same coins to the network, Eve issues only Alice's payment request to the network, while the accomplice tries to mine a block that includes the payment to Bob instead of Alice. There is a positive probability that the rogue miner will succeed before the network, in which case the payment to Alice will be rejected. As with the plain race attack, Alice can reduce the risk of a Finney attack by waiting for the payment to be included in the blockchain.
Each block that is added to the blockchain, starting with the block containing a given transaction, is called a confirmation of that transaction. Ideally, merchants and services that receive payment in bitcoin should wait for at least one confirmation to be distributed over the network, before assuming that the payment was done.
Deanonymisation is a strategy in data mining in which anonymous data is cross-referenced with other sources of data to re-identify the anonymous data source. Along with transaction graph analysis, which may reveal connections between bitcoin addresses pseudonyms , [20] [25] there is a possible attack [26] which links a user's pseudonym to its IP address.
If the peer is using Tor , the attack includes a method to separate the peer from the Tor network, forcing them to use their real IP address for any further transactions. The attack makes use of bitcoin mechanisms of relaying peer addresses and anti- DoS protection. Each miner can choose which transactions are included in or exempted from a block. Upon receiving a new transaction a node must validate it: To carry out that check the node needs to access the blockchain.
Any user who does not trust his network neighbors, should keep a full local copy of the blockchain, so that any input can be verified. As noted in Nakamoto's whitepaper, it is possible to verify bitcoin payments without running a full network node simplified payment verification, SPV.
A user only needs a copy of the block headers of the longest chain, which are available by querying network nodes until it is apparent that the longest chain has been obtained.
Then, get the Merkle branch linking the transaction to its block. Linking the transaction to a place in the chain demonstrates that a network node has accepted it, and blocks added after it further establish the confirmation. While it is possible to store any digital file in the blockchain, the larger the transaction size, the larger any associated fees become.
The use of bitcoin by criminals has attracted the attention of financial regulators, legislative bodies, law enforcement, and the media. Senate held a hearing on virtual currencies in November Several news outlets have asserted that the popularity of bitcoins hinges on the ability to use them to purchase illegal goods. A CMU researcher estimated that in , 4. Due to the anonymous nature and the lack of central control on these markets, it is hard to know whether the services are real or just trying to take the bitcoins.
Several deep web black markets have been shut by authorities. In October Silk Road was shut down by U. Some black market sites may seek to steal bitcoins from customers.
The bitcoin community branded one site, Sheep Marketplace, as a scam when it prevented withdrawals and shut down after an alleged bitcoins theft. Several AIB suppliers are also motherboard suppliers. Video card shipments peaked at a total of million in By contrast, they totalled The sales of video cards have trended downward due to improvements in integrated graphics technologies; high-end, CPU-integrated graphics are able to provide performance competitive with low-end video cards.
At the same time, video card sales have grown within the high-end segment, as manufacturers have shifted their focus to prioritize the gaming and enthusiast market. Beyond the gaming and multimedia segments, video cards have been increasingly used for general-purpose computing , such as big data processing.
In January , mid-to-high-end video cards experienced a major surge in price, with many retailers having stock shortages due to the significant demand among this market. A modern video card consists of a printed circuit board on which the components are mounted.
A graphics processing unit GPU , also occasionally called visual processing unit VPU , is a specialized electronic circuit designed to rapidly manipulate and alter memory to accelerate the building of images in a frame buffer intended for output to a display. Because of the large degree of programmable computational complexity for such a task, a modern video card is also a computer unto itself.
A heat sink is mounted on most modern graphics cards. A heat sink spreads out the heat produced by the graphics processing unit evenly throughout the heat sink and unit itself. The heat sink commonly has a fan mounted as well to cool the heat sink and the graphics processing unit. Not all cards have heat sinks, for example, some cards are liquid cooled, and instead have a waterblock; additionally, cards from the s and early s did not produce much heat, and did not require heatsinks.
Most modern graphics cards need a proper thermal solution. This can be the liquid solution or heatsinks with an additional connected heat pipe usually made of copper for the best thermal transfer. It should also be noted that the correct case; either Mid-tower or Full-tower or some other derivative, has to be properly configured for thermal management.
This can be ample space with proper push pull or opposite configuration as well as liquid with a radiator either in lieu or with a fan setup. The video BIOS or firmware contains a minimal program for initial set up and control of the video card. It may contain information on the memory timing, operating speeds and voltages of the graphics processor, RAM, and other details which can sometimes be changed. The usual reason for doing this is to overclock the video card to allow faster video processing speeds, however, this has the potential to irreversibly damage the card with the possibility of cascaded damage to the motherboard.
The modern Video BIOS does not support all the functions of the video card, being only sufficient to identify and initialize the card to display one of a few frame buffer or text display modes.
It does not support YUV to RGB translation, video scaling, pixel copying, compositing or any of the multitude of other 2D and 3D features of the video card. Around , the video memory was typically based on DDR technology.
Video memory may be used for storing other data as well as the screen image, such as the Z-buffer , which manages the depth coordinates in 3D graphics , textures , vertex buffers , and compiled shader programs. The RAMDAC , or random-access-memory digital-to-analog converter, converts digital signals to analog signals for use by a computer display that uses analog inputs such as cathode ray tube CRT displays.
Depending on the number of bits used and the RAMDAC-data-transfer rate, the converter will be able to support different computer-display refresh rates. These require a RAMDAC, but they reconvert the analog signal back to digital before they can display it, with the unavoidable loss of quality stemming from this digital-to-analog-to-digital conversion.
Some problems of this standard are electrical noise , image distortion and sampling error in evaluating pixels. Today, the VGA analog interface is used for high definition video including p and higher.
While the VGA transmission bandwidth is high enough to support even higher resolution playback, there can be picture quality degradation depending on cable quality and length.
Digital-based standard designed for displays such as flat-panel displays LCDs , plasma screens, wide high-definition television displays and video projectors. It avoids image distortion and electrical noise, corresponding each pixel from the computer to a display pixel, using its native resolution. Included to allow connection with televisions , DVD players , video recorders and video game consoles.
The interface is primarily used to connect a video source to a display device such as a computer monitor , though it can also be used to transmit audio, USB, and other forms of data. Backward compatibility to VGA and DVI by using adapter dongles enables consumers to use DisplayPort fitted video sources without replacing existing display devices. Although DisplayPort has a greater throughput of the same functionality as HDMI , it is expected to complement the interface, not replace it.
In the following table is a comparison between a selection of the features of some of those interfaces.