GnuPG - GnuPG is a complete and free implementation of the OpenPGP standard as defined by RFC4880 (also known as PGP).
SpeedCrunch - SpeedCrunch. SpeedCrunch is a high-precision scientific calculator featuring a fast, keyboard-driven user interface. It is free and open-source software, licensed under the GPL. Download Documentation Donate .
Kleopatra - Kleopatra is a certificate manager and GUI for GnuPG.
Soulver - Soulver is a software application that functions as a calculator that allows you type a continuous stream of information rather than having to input data into multiple cells.
PGP Tool - PGPTool allows you to encrypt and decrypt files. It's free and easy to use.
Qalculate! - Qalculate! is a multiplatform multi-purpose desktop calculator.