There are three types of Bitcoin addresses. Each can be used to send funds to the other kinds of addresses. Each Bitcoin address is between 26 and 35 characters long.
The first, called P2PKH (Pay to PubKey Hash), is Bitcoin’s original address format. It always begins with a number 1 and will look something like this: 13GNnQg8ghsa4U1CVrz8BaqToFUL1yFWQ7.
The second is called P2SH (Pay to Script Hash) and looks a lot like a P2PKH address, except that it begins with a number 3. P2SH addresses are often used where multiple signatures are needed to authorise transactions.
The third is called Bech32 and begins with ‘bc1’. They were created as part of the August 2017 SegWit soft fork of Bitcoin and are much are less common than P2PKH or P2SH addresses.
Bitcoin allows you to create as many addresses as you like, and use that address for each transaction.
Open source tools like BitAddress.org can randomly generate new Bitcoin addresses, along with the private key you need to access them.
Bitcoin addresses were not originally designed to be re-used, but it does happen.
Re-used Bitcoin addresses commonly belong to exchanges, because there are many people sending cryptocurrencies to exchanges and receiving coins back from them.
Bitcoin addresses are linked to Bitcoin wallets, but they are not the same thing. A Bitcoin address represents the public key part of an asymmetric key pair. On the other side of this pair is your private key, which allows Bitcoins to be spent.
A wallet contains a list of your public and private keys.
Public-key cryptography underpins how blockchains and Bitcoin work.
A public key, which can be shared, is used to encrypt a Bitcoin transaction and is a randomly generated number that corresponds to a private key.
A private key, which should always remain secret, is used to decrypt or decode Bitcoin transactions.
A private key for a P2PKH Bitcoin address will look something like this: Kwhzc12imyGa7hhcdrokLwjYpJAGDYDqw6kwRNY78tcyiD2VkNvu
The cryptographic algorithm used by Bitcoin to make sure that coins can only be spent by the people who own them is called the Elliptic Curve Digital Signature Algorithm, or ECDSA. Bitcoin uses the sepcp256k1 curve. There’s more about that here, if you’re mathematically minded and want to know more.
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