Off-the-record communication, or, why not to use PGP
Nikita Borisov, Ian Goldberg, Eric Brewer · 2004
Quite often on the Internet, cryptography is used to protect private, personal communications. However, most commonly, systems such as PGP are used, which use long-lived encryption keys (subject to compromise) for confidentiality, and digital signatures (which provide strong, and in some jurisdictions, legal, proof of authorship) for authenticity.