GPG Commands - Encrypt, Decrypt, Sign, and Manage Keys - cmd Cheatsheets

This guide provides essential GPG (GNU Privacy Guard) commands for managing cryptographic keys and performing secure operations like encryption, decryption, and signing. GPG is a powerful tool for ensuring data confidentiality and integrity.

GPG Key Management

Effectively managing your GPG keys is crucial for secure communication. This section covers generating, listing, exporting, and importing keys.

# Create a new GPG key pair
 gpg --gen-key

# List all keys (public and secret)
 gpg --list-keys
 gpg -k

# List only secret keys
 gpg --list-secret-keys
 gpg -K

# Show your public key in ASCII armor format
 gpg --armor --export

# Show the fingerprint for a specific key
 gpg --fingerprint KEY_ID

# Search for keys on public key servers
 gpg --search-keys 'user@emailaddress.com'

File Encryption and Decryption

Learn how to encrypt files for specific recipients and decrypt files that have been encrypted using GPG.

# Encrypt a file for a specific recipient
 gpg --encrypt --recipient 'user@emailaddress.com' example.txt

# Decrypt a file
 gpg --output example.txt --decrypt example.txt.gpg

Exporting and Importing Keys

Securely export your public and private keys for backup or sharing, and import keys from others.

# Export your public key
 gpg --output ~/public_key.txt --armor --export KEY_ID

# Export your secret key (handle with extreme care)
 gpg --output ~/private_key.txt --armor --export-secret-key KEY_ID

# Securely delete the private key file after export
 shred -zu ~/private_key.txt

# Import a public key
 gpg --import ~/public_key.txt

# Import a secret key (requires special flag)
 gpg --allow-secret-key-import --import ~/private_key.txt

# Securely delete the imported private key file after import
 shred -zu ~/private_key.txt

Revoking a GPG Key

If your private key is compromised or you no longer wish to use a key, you should revoke it.

# Create a revocation certificate
 gpg --output ~/revoke.asc --gen-revoke KEY_ID

# Import the revocation certificate
 gpg --import ~/revoke.asc

# Send the revocation to key servers
 gpg --send-keys KEY_ID

Signing and Verifying Files

GPG can be used to digitally sign files to verify their authenticity and integrity.

# Sign a file (creates a .asc signature file)
 gpg -ba filename

# Sign a file with a specific default key
 gpg --default-key <key ID> -ba filename

# Verify a downloaded file using its signature
 gpg --verify filename.asc

Signing Public Keys

Contribute to the web of trust by signing the public keys of others.

# Retrieve a public key from a keyserver
 gpg --keyserver <keyserver> --recv-keys <Key_ID>

# Check the key's fingerprint
 gpg --fingerprint <Key_ID>

# Sign the key
 gpg --sign-key <Key_ID>

# Upload the signed key to a keyserver
 gpg --keyserver <keyserver> --send-key <Key_ID>

Managing GPG Key UIDs (User IDs)

Modify the email addresses and names associated with your GPG keys.

# Edit a key
 gpg --edit-key <key ID>

# Add a new User ID (name and email)
 adduid

# List current UIDs
 list

# Select a UID to delete
 uid <list number>

# Delete the selected UID
 deluid

# Save changes
 save

# Publish the updated key to a server
 gpg --send-keys <key ID>

Creating and Managing Subkeys

Subkeys offer flexibility by allowing you to keep your master key secure while using subkeys for specific purposes or machines.

# Edit a key to add subkeys
 gpg --edit-key <key ID>

# Add a signing-only subkey
 addkey
 # Choose RSA, 4096 bits, and set an expiry period.

# Add an encryption-only subkey (repeat addkey process)

# Save changes
 save

# Export secret subkeys
 gpg --export-secret-subkeys <subkey ID> > subkeys
 gpg --export <key ID> > pubkeys

# Delete the master secret key
 gpg --delete-secret-key <key ID>

# Import the master public key and secret subkeys
 gpg --import pubkeys subkeys

# Verify that subkeys are now present (should show sec#)
 gpg -K

High-Quality Symmetric Encryption Options

For enhanced security in symmetric encryption, consider these advanced GPG options.

# Encrypt a file using high-quality symmetric options
 gpg \
    --symmetric \
    --cipher-algo aes256 \
    --digest-algo sha512 \
    --cert-digest-algo sha512 \
    --compress-algo none -z 0 \
    --s2k-mode 3 \
    --s2k-digest-algo sha512 \
    --s2k-count 65011712 \
    --force-mdc \
    --pinentry-mode loopback \
    --armor \
    --no-symkey-cache \
    --output somefile.gpg \
    somefile # file to encrypt

# Decrypt a file using high-quality symmetric options
 gpg \
    --decrypt \
    --pinentry-mode loopback \
    --armor \
    --output somefile.decrypted \
    somefile.gpg # file to decrypt

gpg

GPG Command Line Guide