GnuPG is a command line tool without any graphical user interface. It is an universal crypto engine which can be used directly from a command line prompt, from shell scripts, or from other programs. Therefore GnuPG is often used as the actual crypto backend of other applications.
Even when used on the command line it provides all functionality needed - this includes an interactive menu system. The set of commands of this tool will always be a superset of those provided by any frontends.
GnuPG is a hybrid-encryption software program because it uses a combination of conventional symmetric-key cryptography for speed, and public-key cryptography for ease of secure key exchange, typically by using the recipient's public key to encrypt a session key which is only used once. This mode of operation is part of the OpenPGP standard and has been part of PGP from its first version.
- Full OpenPGP implementation (see RFC4880 at RFC Editor).
- Full CMS/X.509 (S/MIME) implementation.
- Ssh-agent implementation
- Runs on all Unix platforms, Windows and macOS.
- A full replacement of PGP; written from scratch.
- Does not use any patented algorithms.
- Freely available under the GPL;
- Can be used as a filter program.
- Better functionality than PGP with state of the art security features.
- Decrypts and verifies PGP 5, 6 and 7 messages.
- Supports RSA, ECDH, ECDSA, EdDSA, Elgamal, DSA, AES, Camellia, 3DES, Twofish, SHA2, and many more algorithms.
- Language support for a load of languages.
- Online help system.
- Optional anonymous message receivers.
- Integrated support for HKP keyservers (sks-keyservers.net).
- and many more things….