GnuPG is a complete and free replacement for PGP. This is the "stable"
version.

GnuPG allows encrypting and signing your data and communication, and
features a versatile key management system as well as access modules
for many public key directories. GnuPG, also known as GPG, is a command
line tool with features for easy integration with other applications.

WWW: https://www.gnupg.org/