GnuPG

GnuPG

Article by Joseph Purcell on May 20, 2014

The GNU Privacy Guard (GnuPG or GPG) is an implementation of the OpenPGP message format for encrypting and decrypting messages.

Setup

Generating a GPG key is easy, it should look something like:

$ gpg --gen-key
gpg (GnuPG) 1.4.14; Copyright (C) 2013 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? 1
RSA keys may be between 1024 and 4096 bits long.
What keysize do you want? (2048) 4096
Requested keysize is 4096 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) 
Key does not expire at all
Is this correct? (y/N) y

You need a user ID to identify your key; the software constructs the user ID
from the Real Name, Comment and Email Address in this form:
    "Heinrich Heine (Der Dichter) <heinrichh@duesseldorf.de>"

Real name: Your Name
Email address: yourname@example.com
Comment: 
You selected this USER-ID:
    "Your Name <yourname@example.com>"

Change (N)ame, (C)omment, (E)mail or (O)kay/(Q)uit? o
You need a Passphrase to protect your secret key.

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: key 823EB930 marked as ultimately trusted
public and secret key created and signed.

gpg: checking the trustdb
gpg: 3 marginal(s) needed, 1 complete(s) needed, PGP trust model
gpg: depth: 0  valid:   2  signed:   0  trust: 0-, 0q, 0n, 0m, 0f, 2u
pub   4096R/823EB930 2014-05-20
      Key fingerprint = F872 B0A0 0950 8EA4 5CEF  7C04 84B3 F297 823E B930
uid                  Your Name <yourname@example.com>
sub   4096R/3489DA32 2014-05-20

Fingerprints

A fingerprint is a quick way to identify a GPG key.

Get a Fingerprint from a key file

$ gpg --with-fingerprint file.pub

Search for a key by fingerprint

$ gpg --search-key 44F9512B

List Keys You Have

$ gpg -K

Or, for more info:

$ gpg -K --keyid-format long --with-fingerprint

Publishing Your Key

Print Your Public Key to Screen

$ gpg --armor --export F10500E6

Submit Your Key to a PKS

http://keyserver.ubuntu.com:11371/

http://pgp.mit.edu/

OR

$ gpg --keyserver keyserver.ubuntu.com --send-keys F10500E6

Where F10500E6 is your key fingerprint.

Reference: http://askubuntu.com/questions/220063/how-to-publish-gpg-key-in-ubuntu-12-10

Importing Someone Else's Key

For you to encrypt data with someone else's public key you must first import it.

(insert how to here)

Encrypting and Decrypting Email

Encrypting an Email

$ gpg --encrypt --recipient 'youremail@example.com' email.txt

And a file called "email.txt.gpg" will be created which you can then send in the body of an email.

Decrypting an Email

You can only decrypt email for which you have the private key. To do so, run:

$ gpg --output email-decrypted.txt --decrypt email.txt.gpg