cyber-security-resources/crypto/gpg_how_to.md

GPG: Generating Keys, Encrypting, and Decrypting Files

Here are step-by-step instructions on how to generate GPG keys, and how to use them to encrypt and decrypt files:

Generating GPG Keys

• Install GPG: If you haven't already, install GPG on your computer. You can do this by following the installation instructions for your operating system.
• Open your terminal: Open your terminal (or command prompt, for Windows) and enter the following command to generate a new GPG key pair:

gpg --full-generate-key

• Choose key type: Choose the key type you want to generate. For most purposes, RSA is a good choice.
• Choose key size: Choose the key size you want to generate. Higher than 2048 bits is the recommended minimum for RSA keys.
• Choose key expiry: Choose when you want the key to expire. It's a good idea to set an expiry date so that you can update your keys regularly.
• Enter your name and email: Enter your name and email address. These will be associated with your GPG key.
• Enter passphrase: Enter a passphrase to protect your key. This passphrase is used to decrypt your private key and should be kept secret.
• Save your key: Once your key is generated, you'll see a message that it has been created. Your public key will be stored in a file with a .asc extension in your home directory, and your private key will be stored in your GPG keyring.

Encrypting and Decrypting Files

• Encrypt a file: To encrypt a file, use the gpg --encrypt command followed by the name of the file you want to encrypt. For example:

gpg --encrypt file1.txt

This will create a new encrypted file with a .gpg extension.

• Decrypt a file: To decrypt a file, use the gpg --decrypt command followed by the name of the encrypted file. For example:

gpg --decrypt file1.txt.gpg

This will decrypt the file and create a new unencrypted file with the original name.

Note: When encrypting a file, you can specify the recipient of the encrypted file using the --recipient option followed by the email address associated with their public key. For example:

gpg --encrypt --recipient omar@example.com file1.txt

This will encrypt the file and make it readable only by Omar, whose public key is associated with the email address omar@example.com.

That's it! You now know how to generate GPG keys and use them to encrypt and decrypt files.