What is GPG?
GNU Privacy Guard—a free, open-source implementation of the OpenPGP standard. GPG provides encryption, digital signatures, and key management. It's the most widely used tool for PGP-compatible email encryption and file signing.
Also known as: GnuPG, GNU Privacy Guard
GPG is PGP for everyone. Where PGP was originally proprietary, GPG is free software—and the de facto standard for OpenPGP operations.
GPG vs. PGP
- PGP: Original commercial product, now owned by Broadcom. The standard.
- GPG (GnuPG): Free, open-source implementation. Fully compatible with PGP.
- OpenPGP: The standard both implement. RFC 4880 and successors.
- In practice: "PGP" and "GPG" are used interchangeably for the same capabilities.
What GPG Does
Encryption
- Encrypt files so only the recipient can read them
- Encrypt email (with mail client integration)
- Asymmetric (public/private key) or symmetric (passphrase only)
Signing
- Digitally sign files or messages to prove authenticity
- Recipients verify the signature with your public key
- Tampering breaks the signature
Key Management
- Generate key pairs
- Import/export public keys
- Revoke compromised keys
- Build and maintain your web of trust
Using GPG
Command Line
gpg --encrypt file.txt— Encrypt for a recipientgpg --sign file.txt— Sign a filegpg --verify file.txt.sig— Verify a signature
With Email
- Thunderbird + OpenPGP extension
- Enigmail (legacy)
- Or use ProtonMail/Tutanota for built-in PGP without GPG setup
Key Servers
- Public keys published to keys.openpgp.org or keyservers
- Others can find your key to encrypt to you
- Consider key expiration and revocation certificates
Related Terms
Encryption
The process of converting information into a code to prevent unauthorized access. Encryption transforms readable data (plaintext) into an unreadable format (ciphertext) using a cryptographic algorithm and key. Only those with the correct key can decrypt and read the original data.
PGP
Pretty Good Privacy (PGP) is an encryption program that provides cryptographic privacy and authentication for data communication. It's used for signing, encrypting, and decrypting texts, emails, files, and directories, and is the gold standard for email encryption.
Public Key Cryptography
A cryptographic system that uses pairs of keys: public keys (which may be disseminated widely) and private keys (which are known only to the owner). This enables secure communication between parties who have never met and forms the basis for digital signatures, key exchange, and encrypted communication.