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OpenPGP Certified


The OpenPGP Web of Trust[edit]

Hauke laging gepruefter artikel.en.png

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256

The OpenPGP Web of Trust

If you want to be extra cautious and really authenticate a OpenPGP key in a stronger way than what standard HTTPS offers you, you could use the OpenPGP Web of Trust.

One of the inherent problems of standard HTTPS is that the trust we usually put on a website is defined by certificate authorities: a hierarchical and closed set of companies and governmental institutions approved by web browser vendors. This model of trust has long been criticized and proved several times to be vulnerable to attacks as explained on our warning page.

We believe instead that users should be given the final say when trusting a website, and that designation of trust should be done on the basis of human interaction.

The OpenPGP Web of Trust is a decentralized trust model based on OpenPGP keys. Let's see that with an example.

You're a friend of Alice and really trust her way of managing OpenPGP keys. You've validated Alice's key.
Furthermore, Alice met Bob in a conference, and signed Bob's key.

This scenario creates a trust path from you to Bob's key that could allow you to validate it without having to depend on certificate authorities.

This trust model is not perfect either and requires both caution and intelligent supervision by users. The technical details of creating, managing and trusting OpenPGP keys are outside of the scope of this document.

We also acknowledge that not everybody might be able to create good trust path since it based on a network of direct human relationships and the knowledge of quite complex tools such as GnuPG.

Because Whonix developer adrelanos prefers to stay anonymous, this trust model is not suited for Whonix.
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v2.0.19 (GNU/Linux)

iQEcBAEBCAAGBQJStjCVAAoJEF8Ejm8OS0SUAr0H/3r0HIpjU8y+SOsEsA81RadJ
jpPzPhUPjvlcV7jeKg8mSZXjF6hKlFe+48V6PwmF8JPW0anwyHsK4vAiRtkc+LDd
w+glrlDLQ0d4Lb2HTD0vCwp9E90FPuVF6oocCUflRQlSgHqoHmF+sqoNiwFLvTmt
Y1aCl9QTnx2CkH1GISJxbGu6j9J/ZoweUE7NNSTdjqZIkgUuEbMoQyCisZ6JFzwl
qZ73ZrGX+t8Az+vPaH5HMOKkl7sDNZveW/Tim/vS5YF1OwXoQjqFnuFiPbZ2+Zrm
yGRejc2x17UOpU26/OGzeO9ky/QBEqrt8ep5GTjn42Wdg0qq095flxvVvkT/SNo=
=4B7I
-----END PGP SIGNATURE-----

Air Gapped OpenPGP Key[edit]

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-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256

Introduction

The high level overview of this concept is as follows:
Shut down your every day operating system. Boot your air gapped operating system. You can boot a Live DVD or an operating system installed on external media such as USB (recommendation: use full disk encryption). Using a separate physical hardware is better than just booting another operating system, but still, using another operating system is better than nothing.
By default GPG creates a signing key as your main key (your identity) and one encryption subkey (how you receive messages intended for you). We will only create a primary singing/certification key.
Use GPG to add an additional encryption and signing subkey to your keypair. These new subkeys are linked to your main key. Now we have two subkeys. Store the whole key in a protected place. Your master keypair is the one whose compromise would be truly catastrophic.
Then create a slave key which won't contain your master key.
Copy your slave key to your every day operating system.


Prerequisites

It is recommended to first quickly read this article from top to bottom without taking actions. After you roughly understood how it's supposed to work, re-read this page and do it step-by-step. Exercise this with test keys first. If that works, consider doing this with your primary keys.
Make backups of your existing GnuPG files ($HOME/.gnupg). Keep them safe. If something goes wrong during the following steps, you may need this to return to a known good place.
You should know how to boot other operating systems than your primary every day operating system from Live DVD and/or other external media such as USB.
Optionally, if your storage medium could get accessed or stolen by an adversary, it is also recommended to learn how to use disk encryption software. As a precaution, it's wise to do this anyway.
Additionally to protect yourself against mistakes it may make sense to manage your gpg master key folder with a version revision system such as git.


Creating your Air Gapped OpenPGP Key

Preparation

Boot your air gapped system.
mkdir ~/gpg-master
mkdir ~/.gnupg
chmod 700 ~/gpg-master
chmod 700 ~/.gnupg
Create a ~/gpg-master/gpg.conf and ~/.gnupg/gpg.conf. Source: gpg.conf optimized for privacy Check if there is a newer version available. It probably makes sense to copy that file to an USB stick beforehand so you don't have to type it by hand.

## gpg.conf optimized for privacy

##################################################################
## BEGIN some suggestions from TorBirdy setting extensions.enigmail.agentAdditionalParam

## Don't disclose the version
no-emit-version

## Don't add additional comments (may leak language, etc)
no-comments

## We want to force UTF-8 everywhere
display-charset utf-8

## Proxy settings
keyserver-options http-proxy=socks5://TORIP:TORPORT

keyserver hkp://qdigse2yzvuglcix.onion

## END some suggestions from TorBirdy TorBirdy setting extensions.enigmail.agentAdditionalParam
##################################################################

##################################################################
## BEGIN Some suggestions from Debian http://keyring.debian.org/creating-key.html

personal-digest-preferences SHA512
cert-digest-algo SHA512
default-preference-list SHA512 SHA384 SHA256 SHA224 AES256 AES192 AES CAST5 ZLIB BZIP2 ZIP Uncompressed

## END Some suggestions from Debian http://keyring.debian.org/creating-key.html
##################################################################

##################################################################
## BEGIN Some suggestions added from riseup https://we.riseup.net/riseuplabs+paow/openpgp-best-practices

## When creating a key, individuals may designate a specific keyserver to use to pull their keys from.
## The above option will disregard this designation and use the pool, which is useful because (1) it
## prevents someone from designating an insecure method for pulling their key and (2) if the server
## designated uses hkps, the refresh will fail because the ca-cert will not match, so the keys will
## never be refreshed.
keyserver-options no-honor-keyserver-url

## when outputting certificates, view user IDs distinctly from keys:
fixed-list-mode

## long keyids are more collision-resistant than short keyids (it's trivial to make a key with any desired short keyid)
keyid-format 0xlong

## when multiple digests are supported by all recipients, choose the strongest one:
## already defined above
#personal-digest-preferences SHA512 SHA384 SHA256 SHA224

## preferences chosen for new keys should prioritize stronger algorithms:
## already defined above
#default-preference-list SHA512 SHA384 SHA256 SHA224 AES256 AES192 AES CAST5 BZIP2 ZLIB ZIP Uncompressed

## If you use a graphical environment (and even if you don't) you should be using an agent:
## (similar arguments as https://www.debian-administration.org/users/dkg/weblog/64)
use-agent

## You should always know at a glance which User IDs gpg thinks are legitimately bound to the keys in your keyring:
verify-options show-uid-validity
list-options show-uid-validity

## include an unambiguous indicator of which key made a signature:
## (see http://thread.gmane.org/gmane.mail.notmuch.general/3721/focus=7234)
sig-notation issuer-fpr@notations.openpgp.fifthhorseman.net=%g

## when making an OpenPGP certification, use a stronger digest than the default SHA1:
## already defined above
#cert-digest-algo SHA256

## END Some suggestions added from riseup https://we.riseup.net/riseuplabs+paow/openpgp-best-practices
##################################################################

##################################################################
## BEGIN Some suggestions from TorBirdy opt-in's

## Up to you whether you in comment it (remove the single # in front of
## it) or not. Disabled by default, because it causes too much complaints and
## confusion.

## Don't include keyids that may disclose the sender or any other non-obvious keyids
#throw-keyids

## END Some suggestions from TorBirdy opt-in's
##################################################################


Creating your Initial Keypair

Use the gpg ‐‐gen-key command to create a new GPG keypair.
When you create your new keypair, use the highest possible values for key length. As computers get more powerful and storage gets cheaper, it’s conceivable that a nasty person could archive a message that’s unbreakable today, then in the future break it using a more powerful computer. Using the highest possible value for key length helps protect you from that scenario. Don’t use GPG’s default of 2048!
To prevent filling up the keyserver with garbage and outdated keys or if something goes wrong, it's recommended to set an expire data on your key.
When prompted for a passphrase, make sure to pick a long and unique one. It will be your passphrase for your master key. (We'll later set a different passphrase for your slave key.) If your key gets stolen, this passphrase is the only thing protecting it! Don't use a passphrase you've ever used on your every day operating system, because that will help you to store a backup of your private master key on your every day operating system and thanks to the passphrase protection, you can even back it up in places without strong guarantees of privacy such as free cloud hosting or you public homepage. Just remember, to never enter the passphrase on your every day operating system.

gpg --homedir ~/gpg-master --gen-key
gpg (GnuPG) 1.4.15; 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.

gpg: keyring `/home/user/gpg-master/secring.gpg' created
gpg: keyring `/home/user/gpg-master/pubring.gpg' created
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) 1y
Key expires at Sun 21 Dec 2014 03:51:23 PM UTC
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: Bilbo Baggins
Email address: bilbo@shire.org
Comment: 
You selected this USER-ID:
    "Bilbo Baggins <bilbo@shire.org>"

Change (N)ame, (C)omment, (E)mail or (O)kay/(Q)uit? o
You need a Passphrase to protect your secret key.
<passphrase>
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:   1  signed:   0  trust: 0-, 0q, 0n, 0m, 0f, 1u
gpg: next trustdb check due at 2014-12-21
pub   4096R/0x310F6FAD4BD6D42A 2013-12-21 [expires: 2014-12-21]
      Key fingerprint = C451 1D27 531E 3B5F E84D  F579 310F 6FAD 4BD6 D42A
uid                 [ultimate] Bilbo Baggins <bilbo@shire.org>
sub   4096R/0x2516E552C8D4D937 2013-12-21 [expires: 2014-12-21]
Have a look at the "pub 4096R/488BA441 2013-03-13" line. In this example 0x2516E552C8D4D937 is your short key id, your key id will differ.


Creating your Signing Sub Key

Now for the special sauce: let’s add our new signing subkey.
Use the gpg ‐‐edit-key command. At the gpg> prompt, enter the command addkey. Select RSA (sign only) and 4096 for the keysize. Don’t forget to save at the last gpg> prompt:

gpg --homedir ~/gpg-master --edit-key 0x2516E552C8D4D937
gpg (GnuPG) 1.4.15; 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.

Secret key is available.

pub  4096R/0x310F6FAD4BD6D42A  created: 2013-12-21  expires: 2014-12-21  usage: SC  
                               trust: ultimate      validity: ultimate
sub  4096R/0x2516E552C8D4D937  created: 2013-12-21  expires: 2014-12-21  usage: E   
[ultimate] (1). Bilbo Baggins <bilbo@shire.org>

gpg> addkey
Key is protected.

You need a passphrase to unlock the secret key for
user: "Bilbo Baggins <bilbo@shire.org>"
4096-bit RSA key, ID 0x310F6FAD4BD6D42A, created 2013-12-21
<passphrase>
Please select what kind of key you want:
   (3) DSA (sign only)
   (4) RSA (sign only)
   (5) Elgamal (encrypt only)
   (6) RSA (encrypt only)
Your selection? 4
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) 1y
Key expires at Sun 21 Dec 2014 03:58:16 PM UTC
Is this correct? (y/N) y
Really create? (y/N) y

pub  4096R/0x310F6FAD4BD6D42A  created: 2013-12-21  expires: 2014-12-21  usage: SC  
                               trust: ultimate      validity: ultimate
sub  4096R/0x2516E552C8D4D937  created: 2013-12-21  expires: 2014-12-21  usage: E   
sub  4096R/0x44FE8C6D8E9594FC  created: 2013-12-21  expires: 2014-12-21  usage: S   
[ultimate] (1). Bilbo Baggins <bilbo@shire.org>

gpg> save


Exporting your Master Key

Now that your keypair has been created, let’s export it so that we can back it up:
gpg --homedir ~/gpg-master --armor --export-secret-keys 0x2516E552C8D4D937 > 0x2516E552C8D4D937.private.gpg-key
gpg --homedir ~/gpg-master --armor --export 0x2516E552C8D4D937 > 0x2516E552C8D4D937.public.gpg-key
This will create two files: your public key and your private key. Backup these two files, as best as you can.


Creating your Slave Key

Export Secret Subkeys

Now we have our master keypair in our keyring, along with two files representing the master keypair plus the keypair’s revocation certificate. To derive our slave keypair from our master keypair, we have to create a copy of our master keypair and remove the master secret key.
Export all of the subkeys from our new keypair to a file:
gpg --homedir ~/gpg-master --armor --export-secret-subkeys 0x2516E552C8D4D937 > subkeys


Create your Slave Key without Master Key

We are now no longer using --homedir ~/gpg-master!
Re-import the sub keys we exported.
gpg --import subkeys
Clean up our temporary file.
rm subkeys
Re-import our public key we exported.
gpg --import 0x2516E552C8D4D937.public.gpg-key
Set a new password for your slave key. Remember, you'll have two different passwords. One for your master key, one for your slave key.
gpg --edit-key 0x2516E552C8D4D937
passwd
...
save
That’s all! You can verify it worked by running:

gpg --list-secret-keys
/home/user/gpg-slave/secring.gpg
- -----------------------------
sec#  4096R/488BA441 2013-03-13
uid                  Bilbo Baggins <bilbo@shire.org>
ssb   4096R/69B0EA85 2013-03-13
ssb   4096R/C24C2CDA 2013-03-13
See how the third line begins with “sec#”, not “sec”? The pound sign means the signing subkey is not in the keypair located in the keyring. Or more correctly said, see footnote. [1]
To make sure everything is alright, use switch gpg's homedir to ~/gpg-master and see if the secret master key is available.
Store your slave key in a file.
gpg --armor --export-secret-subkeys 0x2516E552C8D4D937 > 0x2516E552C8D4D937.secret-subkeys.gpg-key
You can now copy your public key, master key and slave key to a disk and import your public key and your slave key to your every day operating system(s).


In Case of Emergency

Should the worst happen and your slave keypair gets lost, compromised or stolen, we need to revoke the subkeys on that keypair.
Unlock your safe-deposit box and get your master keypair out.
Boot a live USB of Debian or your distro of choice. Then, import your master keypair into the live USB’s keyring:

gpg --import /path/to/0x2516E552C8D4D937.public.gpg-key /path/to/0x2516E552C8D4D937.private.gpg-key

Now use gpg ‐‐edit-key to interactively revoke your subkeys:

gpg --edit-key 0x2516E552C8D4D937
gpg (GnuPG) 1.4.11; Copyright (C) 2010 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.

Secret key is available.

pub  4096R/488BA441  created: 2013-03-13  expires: never       usage: SC  
                     trust: ultimate      validity: ultimate
sub  4096R/69B0EA85  created: 2013-03-13  expires: never       usage: E   
sub  4096R/C24C2CDA  created: 2013-03-13  expires: never       usage: S   
[ultimate] (1). Bilbo Baggins <bilbo@shire.org>

gpg> key 1

pub  4096R/488BA441  created: 2013-03-13  expires: never       usage: SC  
                     trust: ultimate      validity: ultimate
sub* 4096R/69B0EA85  created: 2013-03-13  expires: never       usage: E   
sub  4096R/C24C2CDA  created: 2013-03-13  expires: never       usage: S   
[ultimate] (1). Bilbo Baggins <bilbo@shire.org>

gpg> key 2

pub  4096R/488BA441  created: 2013-03-13  expires: never       usage: SC  
                     trust: ultimate      validity: ultimate
sub* 4096R/69B0EA85  created: 2013-03-13  expires: never       usage: E   
sub* 4096R/C24C2CDA  created: 2013-03-13  expires: never       usage: S   
[ultimate] (1). Bilbo Baggins <bilbo@shire.org>

gpg> revkey

Do you really want to revoke the selected subkeys? (y/N) y
Please select the reason for the revocation:
  0 = No reason specified
  1 = Key has been compromised
  2 = Key is superseded
  3 = Key is no longer used
  Q = Cancel
Your decision? 1
Enter an optional description; end it with an empty line:
> 
Reason for revocation: Key has been compromised
(No description given)
Is this okay? (y/N) y

You need a passphrase to unlock the secret key for
user: "Bilbo Baggins <bilbo@shire.org>"
4096-bit RSA key, ID 488BA441, created 2013-03-13
<passphrase>

You need a passphrase to unlock the secret key for
user: "Bilbo Baggins <bilbo@shire.org>"
4096-bit RSA key, ID 488BA441, created 2013-03-13
<passphrase>

pub  4096R/488BA441  created: 2013-03-13  expires: never       usage: SC  
                     trust: ultimate      validity: ultimate
This key was revoked on 2013-03-13 by RSA key 488BA441 Bilbo Baggins <bilbo@shire.org>   
sub  4096R/69B0EA85  created: 2013-03-13  expires: never       usage: E
This key was revoked on 2013-03-13 by RSA key 488BA441 Bilbo Baggins <bilbo@shire.org>   
sub  4096R/C24C2CDA  created: 2013-03-13  expires: never       usage: S   
[ultimate] (1). Bilbo Baggins <bilbo@shire.org>

gpg> save
Now that your subkey has been revoked, you have to tell the world about it by distributing your key to a keyserver, then you have to add new subkeys.


Other Interesting Stuff

Backups

Make sure you always have a backup of your master key in case one USB stick breaks down. Maybe you like to use paperkey (in debian) for that purpose.


Smartcards

You can then use the smartcard on your everyday system without risk of > exposing the private keys (i.e. they cannot br copied from the smartcard but it is possible to abuse them on the smartcard which can cause less but severe damage, too). Smartcards are worth checking out, but outside the scope of this guide.


Security Considerations

You can skip this if you are not interested in this! This is just a justification why we do things as we do.
Alex Cabal's original text recommends to use gpg --delete-secret-key. We're not using this for two reasons.
Securely wiping of data is a difficult issue. We believe it is safer to create a new keypair (a new secring.gpg) than trusting gpg to remove the private master key from secring.gpg. This is just an assumption, could be FUD.
Users may confuse the gpg-master homedir from their gpg-slave homedir after using like ten times the gpg-master homedir. When they don't carefully read, they could accidentally delete their master key.
Our every day operating system never gets to see our OpenPGP master key, because we regard our every day operating system to be untrusted for these purposes.
Alex Cabal's original text uses gpg e-mail@address, we're using short key ids to avoid user mistakes when editing more complex keys.
Alex Cabal's original text uses gpg setpref and we're using a gpg config file to have these settings enforced already during key creation.


Footnotes

↑ The pound sign means that the mainkey has been replaced by a stub.
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v2.0.19 (GNU/Linux)

iQEcBAEBCAAGBQJStgboAAoJEF8Ejm8OS0SUeVQH/1/LoitKxcB26GH08X1JurgS
hZRpe87P/olctXk1nWjDSjgpDLDir1OOPKgkH8aDq54nITZUI8CK2LDgTZHNTBSt
XX+GpUhdr7EiqtPMnOZY2rpLDcn6nvytwNlbtpDkIrrHa/EVbV4ESPMvIohqTh6s
RCkJJ+/oy0N0Yc/+Y4QQPl/UA5voWPo4ANh/IqfwhKPNWa+JWvsPOPSwL7fRsEVH
GT04Y871rLuxBV7SfZxJauXwtTDnaF/cqUrvlY21sIIZZ/94QwwOPEo+MxN9dI0O
0N66rkOP1gAdEi+1dvjb3ISiJqbCZi9ztZDdNsxF/Q2HlNTSJq4Q7so5K23MUVA=
=9kZI
-----END PGP SIGNATURE-----

License[edit]

The certification image (hauke_laging_gepruefter_artikel.en.png) is copyrighted by Hauke Laging.


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