John Reed
Installing
GnuPG is a complete and free implementation of the OpenPGP standard as defined by RFC4880 (also known as PGP). In addition to the source code being available, GPG also lives in Ubuntu’s repositories.
sudo aptitude install gnupg2
Generating a private key
gpg2 --gen-key
The private key is stored in ~/.gnupg/secring.gpg.
Key management
Exporting keys
The -armor option exports the keys in ASCII format instead of binary.
Public key
gpg2 --armor --output public.key --export 'User Name'
Private key
gpg2 --armor --output private.key --export-secret-key -a 'User Name'
Importing keys
Public key
gpg2 --import public.key
Private key
gpg2 --allow-secret-key-import --import private.key
Deleting keys
Private key
gpg2 --delete-secret-key 'User Name'
Public key
gpg2 --delete-key 'User Name'
Listing keys
Private keys
gpg2 --list-secret-keys
Public keys
gpg2 --list-keys
Encrypting/Decrypting files
Using a password
Encrypting
gpg2 --cipher-algo AES256 --symmetric example_file.txt
Decrypting
gpg2 example_file.txt.gpg
Using a key
For personal use
Encrypting
gpg2 -e -r 'Your Name' example_file.txt
Decrypting
gpg2 example_file.txt.gpg
You will be prompted to enter the password that you used to protect your private key when you created it (if you used one).
For someone else
Encrypting
gpg2 -e -r 'Your Name' example_file.txt
You’ll need to have already imported their public key before you can encrypt a file for them.
Decrypting
gpg2 example_file.txt.gpg
Only the recipient’s private key will be able to decrypt the encrypted file.