Public Key
In simple terms
A public key is like your email address for cryptocurrency—you can safely share it with anyone who wants to send you crypto. Just as people need your email to contact you, they need your public key to transfer money to your wallet.
Definition
An address used to receive crypto.
In depth
A public key is one half of a cryptographic key pair, generated through asymmetric encryption algorithms (typically ECDSA or EdDSA), that serves as a publicly shareable address for receiving transactions. It is mathematically derived from a private key but computationally infeasible to reverse-engineer, ensuring security without compromising the address's visibility. When a transaction is broadcast to the network and validated by nodes or validators, the public key identifies the recipient's account on the distributed ledger. The corresponding private key must sign transactions to prove ownership, while the public key allows anyone to verify the signature's authenticity without exposing the private key.
How does Public Key work?
A public key is calculated from a private key by elliptic-curve multiplication, a one-way operation that cannot practically be run backwards. Wallets then shorten and obscure it into an address: Bitcoin hashes the public key, while Ethereum takes the last twenty bytes of a hash of it. Others send funds to that address. When those funds are later spent, the wallet publishes a signature, and nodes use the public key to confirm the signature could only have come from the matching private key. Sharing a public key or address lets people pay you and verify you, never spend for you.
An example
Illustrative example: someone gives an employer an address derived from their public key and is paid $400 in a stablecoin. Anyone can look that address up on a block explorer and watch the $400 arrive, because chain data is public. Nobody can move it without the private key. The address behaves like a transparent account number: safe to publish, useless for withdrawal.
Figures are illustrative only.
What beginners get wrong
- Treating an address as a secret misunderstands the design; it is public, and explorers show every transaction it has ever made.
- Reusing one address for everything links all activity into a single trail that anyone can follow.
- When asked for an address, some people send a private key instead; the private key should never be given to anyone, for any reason.
- Copying an address by hand or from a truncated display invites a single wrong character that sends funds somewhere unrecoverable.
Related terms
Part of
How do crypto wallets and self-custody work? — the subject page for wallets and self-custody, with all 13 of its definitions in one place.
Educational only — not financial advice.