What Is a Public Key?

A public key is a cryptographic value calculated from a private key using a one-way function, meaning it can be produced from the private key but never used to work backward to it. That property is what makes it safe to hand out.

A calculation that only runs one direction

The private key is a large random number. The public key comes from feeding that number through a fixed mathematical operation on an elliptic curve. Doing that calculation is fast and produces the same public key every time. Reversing it — starting from the public key and solving for the private key — is not something existing computers can do in any practical span of time. Both keys are mathematically linked, but only one of them can be derived from the other.

From key to receiving address

Wallets typically don't display the raw public key. They run it through additional hashing and encoding to produce the shorter address you actually give out. That address is still built entirely from the public key, so anyone sending a transaction is really sending to a destination defined by it. Nothing about this process touches or exposes the private key.

Why exposure isn't a risk here

Every address on a decentralized network is visible to anyone who looks, along with the transactions attached to it. That visibility is by design — it's how the network verifies balances and history without a central record-keeper. What stays private is the one value the public key can't produce: the private key itself. Sharing an address so someone can send you a digital asset doesn't hand them any authority over what's already there.

For how the private key side of this pairing is generated and protected, see Key Security, and for how terms like these connect, see the glossary.