GPG Cheat Sheet

GPG (GNU Privacy Guard) is a free implementation of the OpenPGP standard for encrypting and signing data. This guide covers key generation, encryption, digital signatures, and key management.

NOTE: GPG uses asymmetric cryptography - you have a public key (shareable) and a private key (keep secret). Others use your public key to encrypt messages only you can decrypt with your private key.

/setup

Generate a new GPG key pair

# Interactive key generation with all options
gpg --full-gen-key

# Quick generation with defaults (RSA, 3072 bits, no expiration)
gpg --gen-key

This creates a ~/.gnupg directory with your keyring:

$ tree ~/.gnupg
~/.gnupg/
├── crls.d/
│   └── DIR.txt
├── dirmngr.conf
├── openpgp-revocs.d/
│   └── XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX.rev
├── private-keys-v1.d/
│   ├── XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX.key
│   └── XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX.key
├── pubring.kbx          # Public keyring
├── random_seed
└── trustdb.gpg          # Trust database

/keys

List your keys

# List public keys
gpg --list-keys

# List private keys
gpg --list-secret-keys

# Show key fingerprints
gpg --fingerprint

Export keys

# Export public key (ASCII armored)
gpg --armor --export your.email@example.com > public-key.asc

# Export private key (keep this secure!)
gpg --armor --export-secret-keys your.email@example.com > private-key.asc

# Export to binary format (smaller)
gpg --export your.email@example.com > public-key.gpg

Import keys

# Import a public key
gpg --import public-key.asc

# Import a private key
gpg --import private-key.asc

# Import from keyserver
gpg --keyserver keyserver.ubuntu.com --recv-keys KEYID

/encrypt&decrypt

Encrypt files

# Encrypt for specific recipient
gpg --encrypt --recipient your.email@example.com document.txt

# Encrypt for multiple recipients
gpg --encrypt -r alice@example.com -r bob@example.com document.txt

# Encrypt and ASCII armor the output
gpg --armor --encrypt --recipient your.email@example.com document.txt

Decrypt files

# Decrypt to stdout
gpg --decrypt document.txt.gpg

# Decrypt to specific file
gpg --decrypt --output decrypted.txt document.txt.gpg

# Decrypt and verify signature
gpg --decrypt --verify signed-document.txt.gpg

/sign

Sign files

# Create detached signature
gpg --detach-sign document.txt

# Sign and encrypt
gpg --sign --encrypt --recipient bob@example.com document.txt

# Clear-text signature (human readable)
gpg --clearsign document.txt

Verify signatures

# Verify detached signature
gpg --verify document.txt.sig document.txt

# Verify inline signature
gpg --verify signed-document.txt.asc

/edit

Edit key properties

# Enter key editing mode
gpg --edit-key your.email@example.com

# Common commands in edit mode:
# - passwd     : Change passphrase
# - expire     : Set expiration date
# - adduid     : Add user ID
# - revuid     : Revoke user ID
# - lsign      : Locally sign
# - trust      : Set trust level
# - save       : Save and exit

Key server operations

# Upload public key to keyserver
gpg --keyserver keyserver.ubuntu.com --send-keys KEYID

# Refresh keys from keyserver
gpg --keyserver keyserver.ubuntu.com --refresh-keys

# Search for keys
gpg --keyserver keyserver.ubuntu.com --search-keys "name@example.com"

/examples

Email Encryption Setup

Configure your email client (Thunderbird, Mutt, etc.) to use GPG:

# For Mutt: Add to ~/.muttrc
set crypt_use_gpgme = yes
set crypt_autosign = yes
set pgp_timeout = 3600

File Backup Encryption

Encrypt sensitive backups before storing:

# Encrypt backup archive
tar czf - ~/important-docs/ | gpg --encrypt -r your@email.com > backup.tar.gz.gpg

# Decrypt and extract
gpg --decrypt backup.tar.gz.gpg | tar xzf -

Git Commit Signing

Sign your git commits for authenticity:

# Configure git to use GPG
git config --global user.signingkey KEYID
git config --global commit.gpgsign true

# Sign individual commits
git commit -S -m "Signed commit message"