A GPG key is a cryptographic key pair used with GNU Privacy Guard to create and verify digital signatures, and sometimes to encrypt data. In software release workflows, the private key signs a build or package, while anyone can use the public key to check that the file really came from the expected maintainer and was not altered.
In cyber security, GPG keys matter because they protect trust. If an attacker steals a signing key, they may be able to produce malicious updates that look legitimate, so defenders treat exposure as a serious incident and rotate the key quickly. GPG keys also appear in supply-chain defenses, package verification, email security, and secure file exchange, where signature checks help detect tampering, impersonation, or forged artifacts.