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What is Bitcoin?
Bitcoin (BTC) is a digital asset and a payment system created by an unidentified programmer, or group of programmers, under the name of Satoshi Nakamoto. Bitcoin was introduced on 31 October 2008 to a cryptography mailing list, and released as open-source software in 2009. There have been several high profile claims to the identity of Satoshi Nakamoto; however, none of them have provided proof beyond doubt that back up their claims.
The system is peer-to-peer and transactions take place between users directly, without an intermediary. These transactions are verified by network nodes and recorded in a public distributed ledger called the blockchain, which uses BTC as its unit of account. Since the system works without a central repository or single administrator, the U.S. Treasury categorizes BTC as a decentralized virtual currency. BTC is often called the first cryptocurrency, although prior systems existed and it is more correctly described as the first decentralized digital currency.
Bitcoins are created as a reward for payment processing work in which users offer their computing power to verify and record payments into a public ledger. This activity is called mining and miners are rewarded with transaction fees and newly created bitcoins. Besides being obtained by mining, bitcoins can be exchanged for other currencies, products, and services. When sending bitcoins, users can pay an optional transaction fee to the miners. In February 2015, the number of merchants accepting BTC for products and services passed 100,000. Instead of 2–3% typically imposed by credit card processors, merchants accepting bitcoins often pay fees in the range from 0% to less than 2%.
A wallet stores the information necessary to transact bitcoins. While wallets are often described as a place to hold or store bitcoins, 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” and allows you to access (and spend) them. BTC uses public-key cryptography, in which two cryptographic keys, one public and one private, are generated. At its most basic, a wallet is a collection of these keys.
There are several types of wallets. Software wallets connect to the network and allow spending bitcoins in addition to holding the credentials that prove ownership. Software wallets can be split further in two categories:
Full clients and lightweight clients
— Full clients verify transactions directly on a local copy of the blockchain (over 65 GB as of April 2016). Because of its size / complexity, the entire blockchain is not suitable for all computing devices.
— Lightweight clients on the other hand consult a full client to send and receive transactions without requiring a local copy of the entire blockchain. This makes lightweight clients much faster to setup and allows them to be used on low-power, low-bandwidth devices such as smartphones. When using a lightweight wallet however, the user must trust the server to a certain degree. When using a lightweight client, the server can not steal bitcoins, but it can report faulty values back to the user. With both types of software wallets, the users are responsible for keeping their private keys in a secure place.
Besides software wallets, 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.
Physical wallets also exist and are more secure, as they store the credentials necessary to spend bitcoins offline. Examples combine a novelty coin with these credentials printed on metal, Others are simply paper printouts. Another type of wallet called a hardware wallet keeps credentials offline while facilitating transactions.