How a public key works
A wallet picks a private key at random and computes the public key from it. The calculation is quick in that direction and not feasible in reverse, which is why the public key can be published.
When the wallet signs a transaction, every node checks the signature against the public key. A valid signature proves that the signer holds the private key, without revealing it.
An address is a shortened form of the public key. On Ethereum, the address is the last 20 bytes of the Keccak-256 hash of the public key, written with 0x in front.
Why public keys matter to a wallet or exchange product
A platform can keep public keys on online servers without putting funds at risk: they are enough to create deposit addresses and to watch balances. In an HD wallet, one extended public key generates a whole series of receiving addresses.
Public keys are not secret, but they are not harmless either. Anyone who knows an address or an extended public key can follow every payment made to it, so a leak is a privacy problem for customers.
Public key, private key or address?
- Private key
- The secret half of the pair. It signs, and whoever holds it controls the assets.
- Wallet address
- A shorter code derived from the public key, in the format of one network. The address is what a payer types or scans.
Where a public key shows up in a platform
Modules that do the work
- Custody & walletsWallets on every major chain, with MPC custody from leading providers or your own keys.
- AuthenticationSign-in, passkeys and second factors for customers and staff, on your identity provider or ours.
Platforms that need it
Where it is written
The laws and standards this page's facts come from.
General information, not legal advice: what applies to you depends on your services and your market.