PGP, short for Pretty Good Privacy, is a cryptographic system used to sign and encrypt data. In security work, its signing feature is often the most important: a PGP signature lets a recipient verify that content came from the expected source and has not been changed since it was signed.
This matters in software distribution, update pipelines, and offline or disconnected environments, where teams rely on signatures to protect against tampering. Defenders use PGP to check release images, packages, and metadata before they are trusted. Attackers may try to bypass that protection by substituting files, influencing trust settings, or weakening the verification path so unsigned or altered content is accepted. PGP does not guarantee that software is safe, but it helps preserve integrity and provenance across the delivery chain.