GnuPG

1. Install

Install gnupg;

        $ sudo prt-get depinst gnupg
        

Create a skeleton configuration to be copied by useradd to each user home directory;

        $ sudo mkdir /etc/skel/.gnupg
        $ sudo cp /usr/share/gnupg/gpg-conf.skel /etc/skel/.gnupg/gpg.conf
        

        $ chmod 700 ~/.gnupg
        $ chmod -R 600 ~/.gnupg/*
        

2. Generate keys

Options for creating a DSA and ElGamal key;

Key Size

the defaults are ok.

Expiring Date

Choose a non-expiring key for your own use. For public at least choose yearly expiration.

Name and Email

Real name and e-mail address used to identify your key.

Comment

Can be empty, make a small comment to help indentify.

Passphrase

Password should use numebers and special chars.

Generate keys;

        $ gpg2 --full-gen-key
        gpg (GnuPG) 2.1.11; Copyright (C) 2018 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.

        Please select what kind of key you want:
           (1) RSA and RSA (default)
           (2) DSA and Elgamal
           (3) DSA (sign only)
           (4) RSA (sign only)
        Your selection? 2
        DSA keys may be between 1024 and 3072 bits long.
        What keysize do you want? (2048) 2048
        Requested keysize is 2048 bits
        Please specify how long the key should be valid.
                 0 = key does not expire
              <n>  = key expires in n days
              <n>w = key expires in n weeks
              <n>m = key expires in n months
              <n>y = key expires in n years
        Key is valid for? (0) 6m
        Key expires at Tue May 30 20:29:36 2017 WEST
        Is this correct? (y/N) y

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

        Real name: User Name
        Email address: user@machine.example.org
        Comment: user at external dot org
        You selected this USER-ID:
            "User Name (user at core) <user@machine.example.org>"

        Change (N)ame, (C)omment, (E)mail or (O)kay/(Q)uit? O
        

This will create the follow files;

        .gnupg/pubring.gpg
        .gnupg/random_seed
        .gnupg/secring.gpg
        .gnupg/trustdb.gp
        

List keys;

        $ gpg --list-keys
        /home/droid/.gnupg/pubring.kbx
        ------------------------------
        pub   dsa3072/EE29B7D3 2016-05-30 [SC] [expires: 2017-05-30]
        uid         [ultimate] User Name (user at core ) <user@machine.example.org>
        sub   elg2112/9BC2DC12 2016-05-30 [E] [expires: 2017-05-30]
        

In this case pub key ID is EE29B7D3, add to .profile;

        export GPGKEY=0xEE29B7D3
        

3. Key Management

Key Management;

        $ gpg --list-keys
        $ gpg --list-secret-keys
        $ gpg --fingerprint
        $ gpg --delete-key UID
        $ gpg --delete-secret-key
        $ gpg --edit-key UID
        

3.1. Edit key

        $ gpg --edit-key KEYID
        adduid
        

3.2. Revoke key

Follow the instructions and then select the user you want to revoque, where N is the UID of the user;

        $ gpg --edit-key KEYID
        uid N
        revuid
        save
        

4. Export and import keys

4.1. Export Key

Public keys can be exported in binary format or ASCII-armored format. To export binary format;

        $ gpg --list-keys
        

        $ gpg --output user.gpg --export user@localhost
        

Generate an ASCII version of your public key;

        $ gpg --armor --output user.asc --export 'User Name'
        

4.2. Export to keyserver

The primary public key's ID is referenced in the pub line after the key size, for example the key created above, the short key ID is EE29B7D3:

        gpg --keyserver search.keyserver.net