A public key is a cryptographic address used to receive crypto. It is derived from your private key through a one-way function. You can share your public key freely. Someone can send you coins without learning anything that would let them spend your coins. The public key verifies signatures made with the private key. When you sign a transaction, the network checks the signature against your public key. If it matches, the transaction is valid. If it does not, the transaction is rejected.

The relationship between private and public keys is asymmetric. Going from private to public is easy. Going from public to private is computationally infeasible. That asymmetry is the foundation of public-key cryptography, which predates Bitcoin by decades. In crypto, your public key is hashed to create your address. Bitcoin uses SHA-256 and RIPEMD-160. Ethereum uses Keccak-256. You can share your address with anyone. Your public key is slightly more sensitive but still safe to reveal. The private key is the one thing you never share. Public keys and addresses are meant to be seen.

Public key facts

• Derived from the private key — one-way function
• Used to verify signatures — confirms transaction authorization
• Hashed to create addresses — shorter and easier to share
• Safe to share — unlike the private key

Public key cryptography is not unique to crypto. It secures websites, messaging apps, and software updates. Bitcoin applied it to money.