GnuPG (with binary name gpg) is an application used for public key encryption using the OpenPGP protocol, but also verification of signatures (cryptographic signatures, that also can validate the publisher if used correctly). To some extend, you could say it’s for OpenPGP what OpenSSL is for X.509 and TLS.
Unlike most Linux distributions (which make heavy use of GnuPG for ensuring untampered software within their package repositories), Mac OS X does not bring GnuPG with the operating system, so you have to install it on your own.
Possible sources are:
- Package manager Homebrew:
brew install gnupg gnupg2 - Package manager MacPorts:
sudo port install gnupg gnupg2 - Install from GPGTools, which also brings GUI applications and integration in Apple Mail