What is a private key?

A private key is a secret cryptographic value used to sign crypto transactions or messages. The corresponding public key can verify a signature without disclosure of the private key.

What does a private key authorize?

In a simple account controlled by one key, access to that key enables valid signatures. Ethereum’s account documentation explains this relationship for externally owned accounts. Network and contract rules still apply: possessing a key does not remove every lock or create a nonexistent balance. Multi-signature arrangements may require more than one key.

Example

Someone who knows only your receiving address can send assets to it. That information does not let them sign on your behalf. An exposed private key puts signing authority at risk.

How it differs from an address and recovery words

An address identifies an account or recipient on a network. A seed phrase may regenerate many keys in a compatible setup; a single private key is not necessarily a backup of the whole wallet. An app password may protect a local key copy, but changing it cannot invalidate a copied key.

Use the public address in a block explorer to examine activity. Do not provide a private key to a form claiming to offer support, searches or balance checks.

The recovery-backup storage guide compares preparation for loss, physical damage and exposure of secrets.