Library · Crypto, word by word · Wallets and keys
What is a public key?
A public key is the shareable half of a crypto key pair, derived from the private key. Others use it to check that a signature really came from the private key, and a wallet address is usually a shortened hash of it.
What it means for you
A public key cannot be used to work backwards to the private key or to spend funds, so sharing it does not give away control. It does link activity to you: anyone holding it, or the address made from it, can follow that account's history on the blockchain.
How it works
A public key is a point on the secp256k1 elliptic curve computed from the private key; the computation cannot feasibly be run backwards. Its job is checking signatures: nodes use it to confirm a transaction was signed with the matching private key. An address is usually a hash of it: Ethereum takes the last 20 bytes of its Keccak-256 hash, and a classic Bitcoin address encodes a hash of it with a version number and a checksum. Bitcoin developer documentation advises against reusing public keys, both for privacy and to limit possible attacks on ECDSA.
Sources: ethereum.org: Ethereum accounts, Bitcoin developer guide: Wallets, Bitcoin developer guide: Transactions · checked 4 October 2026
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