A GPG signing key is a cryptographic key used to create digital signatures on software artifacts such as release archives, package files, and update metadata. Those signatures let users, package managers, and automation verify that a file really came from the expected publisher and has not been altered since it was signed.
In cyber security, signing keys are central to software supply-chain trust. Attackers may try to steal a key, abuse a leaked subkey, or replace signed files with unsigned or forged ones. Defenders protect signing keys with hardware tokens, access controls, key rotation, and revocation procedures. If a key is exposed or mishandled, revoking it stops verifiers from trusting old signatures, while a new key re-establishes integrity for future releases. Because a signing key can validate many downloads at once, its compromise can have far wider impact than a single stolen credential.