How to Generate and Manage GPG Keys on Ubuntu 18.04 | 16.04

In some cases you may need to generate and manage GPG keys on Ubuntu Linux servers or desktops. As you may already know, GPG encryption helps keep files save and secure.

Using GPG encryption to encrypt your data before transfer ensures that they will not be viewed or read by anyone without a valid matching key pair. This technology works across diverse platforms, including Windows, Mac OS and Linux.

This brief tutorial shows students and new users how to generate and mange GPG keys on Ubuntu servers or desktops.

When you’re ready to get GPG working on Ubuntu, follow the steps below:

Step 1: Install GnuPG

In order to use GPG encryptions, you will have to install a software that helps generate and manage your GPG encryptions and keys. On Linux systems, a popular tool to help with GPG is GnuPG.

GnuPG is a free software implementation of the OpenPGP standard that allows you to encrypt and sign your data and communications using GPG encryptions.

On Ubuntu, open your command line terminal and run the commands below to install GnuPG.

sudo apt update
sudo apt install gnupg

After installing GnuPG, run the commands below to see if it’s installed and which encryption algorithms are supported. run the commands below:

gpg --help

Output:
gpg --help
gpg (GnuPG) 2.2.4
libgcrypt 1.8.1
Copyright (C) 2017 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Home: /home/richard/.gnupg
Supported algorithms:
Pubkey: RSA, ELG, DSA, ECDH, ECDSA, EDDSA
Cipher: IDEA, 3DES, CAST5, BLOWFISH, AES, AES192, AES256, TWOFISH,
CAMELLIA128, CAMELLIA192, CAMELLIA256
Hash: SHA1, RIPEMD160, SHA256, SHA384, SHA512, SHA224
Compression: Uncompressed, ZIP, ZLIB, BZIP2

Syntax: gpg [options] [files]
Sign, check, encrypt or decrypt
Default operation depends on the input data

Step 2: Generating Your GPG Key Pair

Now that GnuPG is installed, you’ll need to generate your own GPG key pair, consisting of a private and public key.

The private key is your master key. It allows you to decrypt/encrypt your files and create signatures which are signed with your private key.

The public key is shared with those who should open and view content you encrypt with your private key and also verifies that the content encrypted with your private key actually come you.

To generate your key pair, run the commands below:

gpg –gen-key
That should initial GPG key generation process. You will be asked your real name and email address to use to identify the key. You should see similar output as below:

gpg --gen-key
gpg (GnuPG) 2.2.4; Copyright (C) 2017 Free Software Foundation, Inc.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Note: Use "gpg --full-generate-key" for a full featured key generation dialog.

GnuPG needs to construct a user ID to identify your key.

Real name: Richard
Email address: admin@example.com
You selected this USER-ID:
    "Richard <admin@example.com>"

Change (N)ame, (E)mail, or (O)kay/(Q)uit? O
We need to generate a lot of random bytes. It is a good idea to perform
some other action (type on the keyboard, move the mouse, utilize the
disks) during the prime generation; this gives the random number
generator a better chance to gain enough entropy.
We need to generate a lot of random bytes. It is a good idea to perform
some other action (type on the keyboard, move the mouse, utilize the
disks) during the prime generation; this gives the random number
generator a better chance to gain enough entropy.
gpg: /home/richard/.gnupg/trustdb.gpg: trustdb created
gpg: key F6A785CA937400D3 marked as ultimately trusted
gpg: directory '/home/richard/.gnupg/openpgp-revocs.d' created
gpg: revocation certificate stored as '/home/richard/.gnupg/openpgp-revocs.d/77B56FA102AECAC136D1C361F6A785CA937400D3.rev'
public and secret key created and signed.

pub   rsa3072 2019-07-01 [SC] [expires: 2021-06-30]
      77B56FA102AECAC136D1C361F6A785CA937400D3
uid                      Richard <admin@example.com>
sub   rsa3072 2019-07-01 [E] [expires: 2021-06-30]

You’ll be prompted to type and confirm your passphrase for the private key.

After that, your keypair should be generated.

Exporting Your Public Key

If you need to export and share your public key to others, you run the commands below. The public key is used to authenticate that the content encrypted by you actually came from you.

It is also used to decrypt the content you encrypted.

gpg --armor --export admin@example.com > public_key.asc

You can also use the commands below to export the key into a readable text file.

gpg --armor --output key.txt --export admin@example.com

You can then send the public key file to those who should get it.

Encrypting and Decrypting Files

To encrypt a file you want to secure, you run the commands below. The public.text file becomes confidential.text.enc protected file.

gpg --encrypt --recipient 'admin@example.com' --output confidential.txt.enc public.txt

You should see an output as below:

Output
gpg: checking the trustdb
gpg: marginals needed: 3  completes needed: 1  trust model: pgp
gpg: depth: 0  valid:   1  signed:   0  trust: 0-, 0q, 0n, 0m, 0f, 1u
gpg: next trustdb check due at 2021-06-30

You can now delete the public.txt file and only have the encrypted version.

Decrypting Files

To decrypt the confidential.txt.enc file using the public key. run the commands below:

gpg --decrypt --output public.txt confidential.txt.enc

You’ll be asked to provide your passphrase to allow access to your private key to be able to decrypt the file.

Enter the key to decrypt.

Output
gpg: encrypted with 3072-bit RSA key, ID 4BFCC6007183FE53, created 2019-07-01
"Richard <admin@example.com>"

The confidenatial.txt.enc file becomes public.txt.

That should do it!

For Windows users, they can use Gpg4win instead.

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