Public keys, private keys, and addresses
Three words that sound interchangeable and aren’t. Get the key pair straight and self-custody finally makes sense under the hood.
Public key, private key, address — they get used interchangeably, and they absolutely aren’t the same. This is the machinery under “self-custody,” and once it clicks, a lot of safety advice stops feeling like superstition and starts feeling obvious.
A key pair, joined at birth
When your wallet creates a key, it actually makes a matched pair. The private key is a secret number only you should ever know. From it, math derives a matching public key — and crucially, the math only runs one way. You can go from private to public effortlessly; going backwards, from public to private, is so hard it’s effectively impossible.
One key proves you own the coins. The other just shows people where to send them.
What each one does
- Private key — keep secret. It’s used to sign transactions, which is how you prove you authorized a payment. Anyone who has it can spend your coins. This is the thing your seed phrase backs up.
- Public key & address — safe to share. Your address is a shortened, shareable form derived from your public key. It’s what you hand out to get paid, and sharing it can never put your coins at risk.
Why this explains the golden rules
Now the advice makes sense. “Never share your seed phrase” means never expose your private keys. “An address is safe to give out” means it’s only the receiving side. “Sign to confirm” means proving ownership without revealing the secret. It’s all one idea: guard the private key with your life, share the public side freely.
The one thing to remember
Your private key is the secret that controls your coins and must never be shared. Your public key and address are safe to hand out — they only let people pay you.