What Is a Public Key?

A public key is a crucial part of Bitcoin and other cryptographic systems. They use something called public-key cryptography. This might sound tricky, but it's simply a specific type of security system, also known as asymmetric cryptography. This is when you have two keys, a private one and a public one.

Let's explain this a bit more. In the world of Bitcoin, you have a secret key, the private key, and a public key that everyone can see. The public key is made from the private key, using a math process called the Elliptic Curve Digital Signature Algorithm (ECDSA). If you use one of the keys to lock something up, which is called encryption, you need the other key to open it, which is called decryption.

In the Bitcoin protocol, a public key is a bit like your mailbox on the Bitcoin network, which is also called the blockchain. So if someone wants to send you Bitcoin, they put it in your mailbox, or your public key. But to access this mailbox and use these Bitcoins, you need your secret private key.

In Bitcoin, a public key is usually shown as a Bitcoin address. This address starts with 1, 3, or bc1. To create a Bitcoin address, you take a public key and apply a math function to it that turns it into an alphanumeric string, a string of letters and numbers. An example of an address would be 1GinkuKexAZM8FzxUQGBz6YCuaRfkE8ofi. This address is like a unique location on the Bitcoin network.

Beyond being a receiving address, the public key is also used to verify the digital signature of a Bitcoin transaction. When you send Bitcoins, you sign the transaction with your private key. This creates a digital signature. When this signature is verified with the public key, it confirms that the transaction is legitimate.

The pairing of public and private keys is very important for Bitcoin. It helps to send and receive Bitcoins, and allows only the person who has the private key to approve their transactions. So, understanding how this works is very helpful for anyone interested in Bitcoin.