The original cryptocurrency and the one that started it all, Bitcoin was created and released in 2008 by Satoshi Nakamoto, an anonymous figure. Bitcoin has the biggest market cap to date around $29 billion, overshadowing all other cryptocurrencies in this world combined. 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 Bitcoin as its unit of account. Since the system works without a central repository or single administrator, Bitcoin is called the first decentralized digital currency. Bitcoin is the largest of its kind in terms of total market value. Bitcoins are created as a reward in a competition in which users offer their computing power to verify and record Bitcoin transactions into the blockchain. This activity is referred to as mining and successful 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. This may expedite the transaction being confirmed. A wallet stores the necessary information to transact Bitcoins. Wallets are often described as a place to hold or store Bitcoins. Bitcoins are inseparable from the blockchain 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. Bitcoin 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. 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.g., transactions that spend coins from multiple inputs indicate that the inputs may have a common owner) and corroborating public transaction data with known information on owners of certain addresses. Additionally, Bitcoin exchanges, where Bitcoins are traded for traditional currencies, may be required by law to collect personal information. To heighten financial privacy, a new Bitcoin address can be generated for each transaction. For example, hierarchical deterministic wallets generate "rolling addresses" for every transaction from a single seed, while only requiring a single passphrase to be remembered to recover all corresponding private keys.