About bitcoin mining
These have come to be known as "altcoins", short for alternative coins, since Bitcoin was the first blockchain and these are derivative of it. These spin offs occur so that new ideas can be tested, when the scope of that idea is outside that of Bitcoin, or when the community is split about merging such changes. Since then there have been numerous forks of Bitcoin. See list of bitcoin forks. The blockchain is a public ledger that records bitcoin transactions.
A novel solution accomplishes this without any trusted central authority: The blockchain is a distributed database — to achieve independent verification of the chain of ownership of any and every bitcoin amount, each network node stores its own copy of the blockchain. This allows bitcoin software to determine when a particular bitcoin amount has been spent, which is necessary in order to prevent double-spending in an environment without central oversight.
Whereas a conventional ledger records the transfers of actual bills or promissory notes that exist apart from it, the blockchain is the only place that bitcoins can be said to exist in the form of unspent outputs of transactions.
Transactions are defined using a Forth -like scripting language. 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. 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. 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; [9] 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 [60] or store bitcoins, [61] 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" [61] 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. On 24 August at block , , Segregated Witness SegWit went live, introducing a new transaction format where signature data is separated and known as the witness.
The upgrade replaced the block size limit with a limit on a new measure called block weight , which counts non-witness data four times as much as witness data, and allows a maximum weight of 4 megabytes. 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, [79] [] 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 Archived from the original on 5 January Retrieved 28 January Retrieved 2 November Archived from the original on 27 October Archived from the original on 2 November Archived from the original on 18 June Retrieved 23 April Archived PDF from the original on 14 October Retrieved 26 August Archived from the original on 11 October Retrieved 11 October Archived from the original on 21 July Archived from the original on 26 March Retrieved 13 October Archived from the original on 15 October And the Future of Money.
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Archived from the original on 6 September Using a public ledger comes with some problems. The first is privacy. How can you make every bitcoin exchange completely transparent while keeping all bitcoin users completely anonymous?
The second is security. If the ledger is totally public, how do you prevent people from fudging it for their own gain? The ledger only keeps track of bitcoin transfers, not account balances.
In a very real sense, there is no such thing as a bitcoin account. And that keeps users anonymous. Say Alice wants to transfer one bitcoin to Bob. That transaction record is sent to every bitcoin miner—i. Now, say Bob wants to pay Carol one bitcoin. Carol of course sets up an address and a key.
And then Bob essentially takes the bitcoin Alice gave him and uses his address and key from that transfer to sign the bitcoin over to Carol:. After validating the transfer, each miner will then send a message to all of the other miners, giving her blessing. The ledger tracks the coins, but it does not track people, at least not explicitly.
The first thing that bitcoin does to secure the ledger is decentralize it. There is no huge spreadsheet being stored on a server somewhere. There is no master document at all. Instead, the ledger is broken up into blocks: Every block includes a reference to the block that came before it, and you can follow the links backward from the most recent block to the very first block, when bitcoin creator Satoshi Nakamoto conjured the first bitcoins into existence.
Every 10 minutes miners add a new block, growing the chain like an expanding pearl necklace. Generally speaking, every bitcoin miner has a copy of the entire block chain on her computer. If she shuts her computer down and stops mining for a while, when she starts back up, her machine will send a message to other miners requesting the blocks that were created in her absence.
No one person or computer has responsibility for these block chain updates; no miner has special status. The updates, like the authentication of new blocks, are provided by the network of bitcoin miners at large. Bitcoin also relies on cryptography.
The computational problem is different for every block in the chain, and it involves a particular kind of algorithm called a hash function. Like any function, a cryptographic hash function takes an input—a string of numbers and letters—and produces an output. But there are three things that set cryptographic hash functions apart:. The hash function that bitcoin relies on—called SHA, and developed by the US National Security Agency—always produces a string that is 64 characters long.
You could run your name through that hash function, or the entire King James Bible. Think of it like mixing paint. If you substitute light pink paint for regular pink paint in the example above, the result is still going to be pretty much the same purple , just a little lighter. But with hashes, a slight variation in the input results in a completely different output:. The proof-of-work problem that miners have to solve involves taking a hash of the contents of the block that they are working on—all of the transactions, some meta-data like a timestamp , and the reference to the previous block—plus a random number called a nonce.
Their goal is to find a hash that has at least a certain number of leading zeroes. That constraint is what makes the problem more or less difficult. More leading zeroes means fewer possible solutions, and more time required to solve the problem. Every 2, blocks roughly two weeks , that difficulty is reset.
If it took miners less than 10 minutes on average to solve those 2, blocks, then the difficulty is automatically increased. If it took longer, then the difficulty is decreased. Miners search for an acceptable hash by choosing a nonce, running the hash function, and checking. When a miner is finally lucky enough to find a nonce that works, and wins the block, that nonce gets appended to the end of the block, along with the resulting hash. Her first step would be to go in and change the record for that transaction.