B.3. Generating a Keypair
To begin using GnuPG, you must first generate a new keypair: a public key and a private key.
To generate a keypair, at a shell prompt, type the following command:
gpg --gen-key |
Since you work with your user account most frequently, you should perform this action while logged in to your user account (not as root).
You see an introductory screen, with key options, including one recommended option (the default), similar to the following:
gpg (GnuPG) 1.2.6; Copyright (C) 2004 Free Software Foundation, Inc. This program comes with ABSOLUTELY NO WARRANTY. This is free software, and you are welcome to redistribute it under certain conditions. See the file COPYING for details. gpg: keyring '/home/user/.gnupg/secring.gpg' created Please select what kind of key you want: (1) DSA and ElGamal (default) (2) DSA (sign only) (5) RSA (sign only) Your selection? |
Most of the screens which require you to choose an option lists the
default option, within parentheses. You can accept the default options
by pressing
In the first screen, you should accept the default option:
(1) DSA and ElGamal. This option allows
you to create a digital signature and encrypt (and decrypt) with two
types of technologies. Type 1 and then press
Next, choose the key size, or how long the key should be. Generally, the
longer the key, the more resistant against attacks your messages
are. The default size, 1024 bits, should be sufficiently strong for most
users, so press
The next option asks you to specify how long you want your key to be
valid. Usually, the default (0 = key does not
expire) is fine. If you do choose an expiration date,
remember that anyone with whom you exchanged your public key also have
to be informed of its expiration and supplied with a new public key. If
you do not choose an expiration date, then you are asked to confirm your
decision. Press
Your next task is to provide a user ID that consists of your name, your email address, and an optional comment. When you are finished, you are presented with a summary of the information you entered.
The next option is to make any changes to the information you just entered. If you are satisfied with your entries, press
Once you accept your choices, you must enter a passphrase.
 | Tip |
|---|---|
Like your account passwords, a good passphrase is essential for optimal security in GnuPG. For example, mix your passphrase with uppercase and lowercase letters, use numbers, or punctuation marks. |
Once you enter and verify your passphrase, your keys are generated, and a message similar to the following is displayed:
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. +++++.+++++.++++++++....++++++++++..+++++.+++++.+++++++.+++++++ +++.++++++++++++++++++++++++++++++++++++++..........................++++ |
When the activity on the screen ceases, your new keys are made and placed in the directory .gnupg in your home directory. To list your keys, use the command:
gpg --list-keys |
You will see something similar to the following:
/home/username/.gnupg/pubring.gpg ----------------------------------------- pub 1024D/B7085C8A 2000-06-18 Your Name <you@example.com> sub 1024g/E12AF9C4 2000-06-18 |
If you created a GnuPG key with version 1.0.6 or lower, exported your private key, and imported it into a new one, you have to explicitly trust your own key to sign items with version 1.0.7 or higher. To trust your key, type the following command (replace <user-id>):
gpg --edit-key <user-id> |
At the Command> prompt type trust and select 5 = I trust ultimately to trust your own key.