What Is a Public Key?
A public key is the half of the pair you are allowed to show. The private key signs. The public key lets anyone check that the signature is real. Your address is usually a shortened, encoded hash of that public key, which is why you can hand out an address all day without handing out spend authority.
How It Actually Works
- Wallets generate a private key (or a seed that becomes many). Math produces the public key. More math produces the address you copy into an exchange.
- On Bitcoin, the public key is often hidden until you spend from that output. On Ethereum, account cryptography is showing every time you send. Neither case makes the public key a secret on par with the seed.
- Hardware devices keep the private half inside the box and pass out signatures and public keys. That split is the whole point of a hardware wallet.
Risks and Common Mistakes
- Pasting a private key or seed into a site that asked for your "public key" in a hurry. Read the words. Support will never need the spend half.
- Assuming address reuse is free. Public keys plus reuse make clustering easier for anyone running an Arkham-style lens.
- Sending to an address you derived incorrectly. One character off is another universe. Use the QR, then check the first and last characters on the device screen.
When It Matters
Every receive, every hardware verification, and any time a stranger asks you to "import" something. The architecture is on my Security page.
Related Terms
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