A public key is a cryptographic code derived from your private key that can be safely shared with anyone. It serves two core functions in cryptocurrency: it allows others to verify your digital signatures (confirming you authorised a transaction) and it is used to generate your wallet address, which is the destination others send funds to. Unlike the private key, the public key carries no risk if exposed — it is mathematically impossible to reverse-engineer the private key from the public key, thanks to elliptic curve cryptography (specifically the secp256k1 curve used by Bitcoin and Ethereum).
The relationship between keys: Private key → Public key → Wallet address. The public key is generated from the private key using a one-way elliptic curve multiplication function. The wallet address is then derived from the public key through hashing (SHA-256 then RIPEMD-160 for Bitcoin), producing a shorter, more user-friendly string. The public key itself is rarely shared directly in modern crypto transactions — your wallet address is the everyday-use equivalent — but the full public key is broadcast to the network each time you sign and send a transaction.
Public keys are at the heart of the crypto ecosystem’s trustless nature: anyone can verify that a transaction was signed by the rightful owner of an address without needing a bank, notary, or any third party. The verification is purely mathematical and instant.
Example: A Bitcoin public key (uncompressed) looks like: 04bfcab... (130 hex characters). When you send BTC, your wallet broadcasts your public key and digital signature; any node on the network can verify your ownership and approve the transaction without knowing your private key.
Learn more: Investopedia — Public Key Cryptography
