Public Key

What is a Public Key?

A public key is the public half of a cryptographic key pair. It is derived from the private key through a one-way mathematical function: computing the public key from the private key is trivial, but reversing the computation is cryptographically infeasible. The public key’s job is to verify — when a wallet signs a transaction with the private key, anyone on the network can check that signature against the public key and confirm it came from the matching key holder, without the private key ever being exposed.

Most blockchains, including Bitcoin and Ethereum, use elliptic curve cryptography (the secp256k1 curve) for this pairing.

Public Key vs Wallet Address

A wallet address is not the public key. The address is a shorter identifier derived from the public key by hashing it:

• Ethereum: the public key is hashed with Keccak-256, and the last 20 bytes become the 0x... address
• Bitcoin: the public key is hashed with SHA-256 and RIPEMD-160 to produce the hashed public key that feeds address encoding

The full derivation chain runs one way only:

seed phrase → private key → public key → wallet address

No step can be reversed to recover the input. That is the entire security model in one sentence.

When You Actually See a Public Key

In everyday wallet use, you almost never handle the public key directly — wallets show addresses because they are shorter and safer to share. But the public key is not exactly a secret either:

• On Ethereum, every signature you broadcast mathematically reveals enough to recover your public key, which is why block explorers can display it for any address that has ever sent a transaction
• On Bitcoin, pay-to-pubkey-hash addresses hide the public key until the first spend from that address reveals it

This is why “never share your public key” is the wrong mental model: the public key is designed to survive exposure. What must never leave your control is the private key and the seed phrase above it.

The Scam Angle

Scammers exploit the vocabulary gap. A classic support-scam script asks you to “share your public key so we can verify your wallet” — no legitimate service needs this, and victims who don’t know which string is which sometimes paste the seed phrase instead. The rule: an address is fine to share, a public key is almost never requested by anything legitimate, and a private key or seed phrase is never asked for — by anyone, for any reason.

Further Reading

• Public Key vs Private Key vs Wallet Address — how scammers weaponize confusion between the three
• Signature Scams Explained — where the public key quietly does its job while you sign