> COMMAND LINE GNUPG MASTERY

1. Installation

Most Linux distributions come with GPG pre-installed. For macOS, use Homebrew to keep the footprint small.

# macOS (using Homebrew)
brew install gnupg

# Ubuntu/Debian
sudo apt install gnupg

# Fedora
sudo dnf install gnupg

2. Generating Your Key Pair

Generate a key pair with maximum control over security parameters.

gpg --full-generate-key

• Algorithm: RSA and RSA (4096 bits) or Ed25519.
• Expiration: 2y recommended.

3. Backup & Key Migration

To move your identity or keep a hard copy offline, you must export both keys.

Exporting Public & Private Keys:

# Export Public Key (Shareable)
gpg --armor --export your-email@example.com > my-public-key.asc

# Export Private Key (KEEP SECRET!)
gpg --armor --export-secret-keys your-email@example.com > my-private-key.asc

Importing Keys on a New System:

# Import both to restore your identity
gpg --import my-public-key.asc
gpg --import my-private-key.asc

4. Managing Contact Keys

To email someone securely, you need their public key.

gpg --import contact_key.asc

5. Encrypting an Email Body

Write your message to message.txt then run:

gpg --encrypt --armor --recipient friend@example.com message.txt

This generates an ASCII block in message.txt.asc for copy-pasting into your email client.

6. Decrypting Received Messages

Decrypt incoming ciphertext saved as secret.asc:

gpg --decrypt secret.asc