Bitcoin glossary
The secret number that controls bitcoin — whoever holds it, owns the coins.
A private key is the secret number that authorizes spending bitcoin from the addresses derived from it. Signatures prove control without revealing the key. In practice, wallets manage keys for you and back them up as a seed phrase.
“Not your keys, not your coins” compresses Bitcoin’s ownership model into six words: bitcoin held by an exchange is controlled by their keys, not yours. Self-custody means holding the keys yourself — with the responsibility that entails.
The live number
Wallets by custody model