In the context of cryptocurrency, a private key is a number that allows users to sign transactions and to generate receiving addresses.

Cryptocurrencies rely heavily on public-key cryptography to protect users’ funds. In fact, this is where their name comes from.

Public-key cryptography involves users generating a very big number (a private key) that would be practically impossible for anyone to guess. Typically, this number is represented as a long string of letters and numbers. Below is an example of a Bitcoin key: