GnuPG Encryption Software

GnuPG (GNU Privacy Guard, often abbreviated as GPG) is a free and open-source implementation of the OpenPGP standard for encrypting and signing data and communications. Originally developed by Werner Koch in 1997 as a free replacement for PGP (Pretty Good Privacy, created by Phil Zimmermann in 1991), GnuPG is funded by the German Federal Office for Information Security (BSI), g10 Code GmbH, and individual donations. GnuPG is compliant with RFC 4880 (OpenPGP) and RFC 6637 (ECC for OpenPGP). Key features: encryption and decryption: symmetric (single passphrase) and asymmetric (public-key) encryption using AES (128/192/256-bit), Twofish, CAST5, Blowfish, 3DES, and Camellia cipher algorithms. Digital signatures: create and verify cryptographic signatures to prove authenticity and integrity of messages, files, and software packages, using RSA, DSA, ECDSA, and EdDSA (Ed25519) algorithms. Key management: generate, import, export, list, edit, sign, and revoke encryption keys, with support for primary keys and subkeys. Key servers: publish and retrieve keys from public key servers using the Web Key Directory (WKD) protocol and HKP protocol. Web of Trust: a decentralized trust model where users sign each other's keys to build a network of trust relationships, with trust levels (unknown, none, marginal, full, ultimate) and trust signatures. Smartcard and hardware token support: GnuPG supports OpenPGP smartcards, YubiKey, Nitrokey, and Kernel-based Crypto API for storing private keys on hardware tokens, preventing key extraction. GPGSM: S/MIME and X.509 certificate management for enterprise email encryption. Agent (gpg-agent): daemon for caching passphrases and managing SSH agent protocol, replacing ssh-agent. scdaemon: smartcard daemon. Debian package signing (apt-get). Git commit signing. Email encryption (Enigmail, GPGTools). GPL-3.0.