| OmniMix • Tutorial • Nyms |
  
|
As you already saw, anonymous remailing is very effective in hiding your true identity. But if you're not only interested
in Usenet communication, it's a one-way ticket, that gives the addressees of your messages no opportunity for an individual
response. That's where nym servers fill in, as they provide you with a net identity of your choice. After creating an account
for 'Jack the Whopper ' all messages from that pseudonym have to be delivered by your nym server, as all replies get to you
through the nym server as well, both ways at your side of the nym server through remailers to preserve your anonymity.
Thus the concept of nym messaging is a lot different from normal anonymous remailing. You have a nym server somewhere in the
wild, which is remote controlled anonymously by you. Sending data to your nym anonymously can be achieved by using the
Mixmaster (Type II) remailer network. But how is it possible to send messages from the nym server back to you, the holder of
the account, without having to uncover your mail address? With the Mixmaster system this can't be done, as the originator of
a message has to know the final destination, which after the creation of a complete multiencrypted message is buried in the
innermost encryption layer. That's why a different kind of remailer strategy has to come into play, the earlier developed
Type I remailers, which support some directives to manipulate given messages and control their forwarding allowing to set up
the required encrypt-and-forward system.
In our case of a reply message you have a message body consisting of two parts, separated by a line, which contains two
asterisks ('**'). The upper part contains a so-called 'reply block', the lower one the data that have to be delivered, e.g.
the complete message, that was sent to your nym. The reply block is equivalent to a complete Type II remailer message and
defines the return path from the nym server to your own mailbox, multilayer encrypted for the single remailers, that have to
be passed on the journey home to you. It is created by you yourself, and no one else will ever be aware of the complete chain
as long as at least one of the involved private remailer keys or passphrases isn't available for the adversary. Removing an
encryption layer here not only uncovers the address of the next remailer in the chain, but possibly some additional commands,
that have to be executed first, like encrypting the data section ('Encrypt-CAST: a_passphrase') or the subject
('Encrypt-Subject: a_passphrase') with a certain passphrase.
Here's a sample reply message, which may be sent by your nym server. Below the double-asterisk line the message directed to
your nym:
--------------------------------------------------------------------------------
::
Anon-To: remailer@pseudo.borked.net
Latent-Time: +1:00
Encrypt-CAST: wiRtSGTmqPEFM+elVgJP9uQTIT1TdkA2tYaLD5hf2rU
::
Encrypted: PGP
-----BEGIN PGP MESSAGE-----
Version: N/A
hQCMAzsxltkRUbsJAQQAkHxTq2gLQ4hCXcD06fFzLpFVma9lnnWGyFIq9MeXk+YG
JkdqR82uHOGzTyg7je8qtJ1xt6asx0USqECG9KFxU5Jg8mVYqUik7BLAQTFzUC5W
...
5/3FLRI+Z7pe71YbySmHrm6H5Ndd7WAxD+bKtOjqe2uZ+yVjIy3huKkIXm5COsu8
mV496t7HuieiOutEQY9E0UppwQAkXCFKR3bWRZzvRwK598Ao3xJVW+Z+CoHGt+41
pm8q0Y5+uA==
=SEvs
-----END PGP MESSAGE-----
**
From: John Doe <john.doe@domain.net>
To: whopper@my_nymserver.net
Subject: Greetings
Hi Jack,
how are you?
--------------------------------------------------------------------------------
Now from remailer to remailer the encryption layers of the reply block diminish, while those of the data section increase.
To make it even more impossible to draw any conclusions from a unique subject, before the final delivery even the subject
gets encrypted, which makes it variable as well.
When a new account is generated OmniMix automatically defines three long random character sequences, which represent
Base64-encoded 256 bit random numbers and serve the following purposes:
| • |
Passphrase for the asymmetrical PGP public/private key pair of the nym.
|
| • |
Seed for the series of passphrases needed as arguments for the 'Encrypt-Subject' and 'Encrypt-CAST' commands
within the reply block(s) (more information on that topic in the chapter 'Passphrase creation for reply blocks').
|
| • |
Subject of the reply mail which is defined in the innermost reply block and encrypted with the 'Encrypt-Subject'
(esub) command before delivery.
|
As there is at least a slight chance, that some mighty one puts several remailer operators under pressure to get their private
keys and passphrases, and finally is able to unveil your mail address and with that your identity from one of the reply blocks,
another way of delivery, namely the posting to a newsgroup, has become established. There's the 'alt.anonymous.messages' group,
which is destined for nothing but the delivery of such messages. It seems nearly impossible for an adversary to surveil all
accesses to that group. A corresponding final/inner reply block would look like
--------------------------------------------------------------------------------
::
Anon-To: mail2news@dizum.com, mail2new@m2n.mixmin.net, mail2news@anon.lcs.mit.edu
Latent-Time: +0:30
Encrypt-CAST: e3ciyB32gzAzeGI77vXcuJ6oWQVNOTvQaZpgeMuLJus
Encrypt-Subject: gVcdbc9KC71M3/lnrVTKY03X/FIxwQW0JzQhCEcbodY
##
Newsgroups: alt.anonymous.messages
Subject: HDDXyoDRb/xmBdXPwMGcpOs42ZRvZyQwHsuIc2e5syP
--------------------------------------------------------------------------------
To ensure an unproblematic processing of your replies all remailers have to meet some requirements. You find the capabilities
of them all in the 'Options' column and 'Remailer-Capabilities' section of the cypherpunk statistics file downloaded from a
pinger service (preset 'cyp_stat.txt' or 'cyp_capa.txt' in the OmniMix directory).
Cypherpunk Latent-Hist Latent Uptime-Hist Uptime Options
------------------------------------------------------------------------
borked 00B200000000 :13 ++++++++++++ 100.0% PR GO ATLEUIN9
dingo 000000000000 :07 ++++++++++++ 99.5% DPRHGOXATLEUIN9
twisty 000000000000 :06 ++++++++++++ 100.0% PRHGOXATLEUIN9
...
Remailer-Capabilities:
$remailer{"borked"} = " cpunk max mix pgp pgponly repgp remix latent hash cut test ek ekx esub inflt50 rhop5 reord post klen1024";
$remailer{"dingo"} = " cpunk mix hybrid middle pgp pgponly latent ek ekx esub cut hash post repgp remix reord ext max test inflt50 rhop5 klen1000";
$remailer{"twisty"} = " cpunk mix hybrid pgp pgponly latent ek ekx esub cut hash post repgp remix reord ext max test inflt75 rhop5 klen1000";
...
Make sure, that all remailers you define for reply chains allow at least
|
| L |
latent (Supports the Latent-Time directive) |
| E |
ekx (Supports Encrypt-3DES,-CAST directives) |
and the last one additionally
|
| U |
esub (Supports the Encrypt-Subject directive) |
but not
|
| D |
middle (Remailer is middleman only and chains to other remailers) |
and, if you intend to post directly to a newsgroup without involving a mail2news gateway
|
| P |
post (Supports news posting (Anon-Post-To or Post)) |
To make the selection of a suitable chain from the remailers list more comfortable, the entries with deficits, that restrict
their usability, are marked by a specific colouring of the 'Type' column:
| • |
green |
P |
(post) |
Not as exit with direct newsgroup posting. Selected as final remailer, they need the definition of a mail2news gateway. |
| • |
yellow |
DU |
(middle / esub) |
Useless as exit remailer. |
| • |
red |
LE |
(latent / ekx) |
Useless for any reply block. |
| • |
blue |
? |
|
Unknown, no data available. |
The color of the 'Key ID' column represents the reliability of the remailer:
| • |
white |
|
100 |
% |
| • |
green |
>= |
98 |
% |
| • |
yellow |
>= |
95 |
% |
| • |
orange |
>= |
90 |
% |
| • |
red |
< |
90 |
% |
| • |
blue |
unknown |
The data of the remailers named above would qualify them as a solid choice for your first attempts.
Though middleman-only remailers have to be avoided as exit hops, in case of 'dingo' this restriction only applies to the
delivery of mail, whereas it's able to post news messages directly and even through some mail2news gateways specified in
its config file. The NoReply Thesaurus
offers you an insight in those config files and other important information on every single remailer.
To filter out the messages meant for you, you have to check for every message in the newsgroup, whether a decoding of its
encrypted subject with the concerning 'Encrypt-Subject' passphrase of one of your nyms leads to the original subject. All
messages that meet this condition have to be downloaded, and the decryption of their bodies presents the mails your nym
server originally received for your account.
It's obvious, that by only downloading relevant messages you give valuable information to an adversary. That's why OmniMix
offers you to fetch randomly some non-matching messages as well. At 'Dummy Messages' you have to specify the approximate
number of 'dummy' messages to pick for every valid nym message. Set it to '0' for only downloading valid messages, or
better to a higher number to leave an adequate amount of wrong tracks. Additionally a random delay ('Dummy Delay') after
each message download helps to protect from finding out valid messages by interval analyses. A favourable value for the
(maximum) delay would be about twice the time range it usually takes to decode a real nym message and transfer the result
to the mail client.
With a sufficient transfer capacity and speed of your Internet connection you should consider installing a local news
server like Hamster and configure it
to download all available messages. Then make OmniMix get all its nym data from there. This way an adversary is kept from
finding out any relevant access information that may weaken the security of your nym activities.
At all those more or less complicated and time-consuming proceedings you are supported by OmniMix.
Please consider, that the repetitive use of a nym account, whether replying to your mail address or better a newsgroup,
can never be as secure as an ordinary one-shot remailer message with its traces vanishing after the transmission is done!
Beyond that you always have to keep in mind, that only one single less secure data exchange with your nym server may be
enough to reveal the originator of all of your former nym's statements! So be very careful when you send any configuration
requests or other messages to the nym server. That's why there is a dedicated remailer chain setting at the 'SetNym' tab,
which should define a really long sequence. Moreover, any message that comes with a 'Nym Message Header' (preset 'O-Nym')
including an argument other than 'No' is supposed to be a nym message, and, if OmniMix isn't able to assign the 'From'
address to a known nym, is rejected. So use this feature to make sure, that messages from your nym with only a spelling
mistake in the 'From' header don't go the 'normal' way.
Now let's set up a nym and send a few messages through it.