What is a public key?

Think of a seal that only you can use, but whose imprint anyone can check for authenticity. That’s roughly how the private and public keys work together: the first creates a digital signature and the second lets everyone else verify it.

When you send crypto, your wallet uses the private key to sign the transaction. The network checks the signature with the matching public key, without needing to know your private key. The signature is tied to the specific transaction data: if that data changes, the check fails.

The public key is derived mathematically from the private key. Going the other way, i.e. finding the private key when you know only the public one, is considered computationally infeasible with today’s conventional methods and properly chosen cryptographic systems.

Why it matters

Thanks to this mechanism, the network can check that a transaction has the required authorization, with no password or bank approval. The public key verifies the signature; it doesn’t sign transactions.

Here’s a common source of confusion: a public key and a wallet address aren’t always the same thing. Depending on the blockchain, the address may be derived by processing the public key or may have a different structure. To receive crypto, you usually share the address your wallet shows under its receive option, not some key you copied from the settings.

What to watch out for

We insist on the distinction between what’s public and what’s secret. Revealing a public key isn’t enough on its own for someone to spend your crypto. Your private key and seed phrase (recovery phrase), on the other hand, are never shared in order to receive money.

“Public” also doesn’t mean there’s no privacy issue. If you publicly link an address to your name, others may be able to track its activity on a public blockchain. Before you share details for a transfer, check the receiving address and the correct network.