OpenPGP

OpenPGP is an open standard that describes a message (file) format originally used by the Pretty Good Privacy (PGP) program, initially developed by Phil Zimmermann in 1991. A number of standard-track Request for Comment documents augment its functionality, one example being PGP/MIME which defines the use of OpenPGP in email via MIME. OpenPGP's encryption can ensure the secure delivery of files and messages, as well as provide verification of who created or sent the message using a process called digital signing. Using OpenPGP for communication requires participation by both the sender and recipient. OpenPGP can also be used to secure sensitive files when they are stored in vulnerable places like mobile devices or in the cloud. OpenPGP is on the Internet Standards Track and is under active development. Many e-mail clients provide OpenPGP-compliant email security as described in RFC 3156. The current base specification is RFC 9580 (July 2024), the successor to RFC 4880. RFC 9580 specifies a suite of required algorithms consisting of X25519, Ed25519, SHA2-256 and AES-128. In addition to these algorithms, the standard recommends X448, Ed448, SHA2-384, SHA2-512 and AES-256. Beyond these, many other algorithms are supported. The additional specification RFC 9980 (June 2026) defines Post-Quantum Cryptography in OpenPGP, based on ML-KEM composite public key encryption and ML-DSA composite public key signatures, both in combination with Elliptic Curve Cryptography (ECC), as well as SLH-DSA as a standalone public key signature scheme.