Definition
A keystore file is a structured file used to store a cryptographic key and related metadata. In common Ethereum wallet formats, it contains an encrypted private key plus details of the encryption and password-based key derivation. It is not simply a public address, and it should be treated as sensitive even when encrypted. Different wallet and validator systems may use incompatible keystore formats.
How It Works
Compatible software reads the file, derives a decryption key from the supplied password, and uses it to recover the stored secret. The encryption password protects that particular file; changing it does not necessarily change the underlying blockchain private key or address. An older copy may therefore remain usable with its older password. A keystore file also does not automatically represent every account derived from a separate recovery phrase.
Key Considerations
Keep secure backups of the file and a reliable way to recover its password, with access controls appropriate to both. Losing either can prevent access when no alternative recovery material exists. Someone who steals the file can attempt password guessing offline, making strong passwords and suitable key derivation important. Do not upload it to an unfamiliar recovery website. If the underlying private key is exposed, merely re-encrypting the file is insufficient. Before migrating wallets, confirm format compatibility and verify the recovered account without disclosing secrets to untrusted services.