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Posted Jan 25, 2000
Authored by napalm | Site napalm.firest0rm.org

Napalm Magazine issue #2 - Quantum Crypto, VPNs, more gh0st.net (Dec 3, 1999).

tags | crypto, magazine
SHA-256 | e017bfdc9ad598287d72b79ac9eb9bec9ba20aff80acfb63ea82ece5b4cb594b


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/\ /^/_ _ __ __ _|^|_ __ ___
/ \/ / _` '_ \/ _` | | '_ ` _ \
/ /\ / (_| |_) (_| | | | | | | |
/_/ \/ \__, .__/\__,_|_|_| |_| |_|

Issue 2 (Dec 3, 1999)
The gh0st.net project: http://www.gh0st.net/index.html
URL of the day: http://www.imagineradio.com
All content copyright © 1999 by the individual authors, All Rights Reserved

- Editor's Comments
- Ramblings
- URLs
- The gh0st.net Project, continued
- Quantum Cryptography
- Securing Your Communications (A Guide to VPNs)
- Future Issues
- Credits

*** Editor's Comments : Kynik

The first issue didn't seem to get all that well circulated, so I'm
working on publicizing everything a bit more. I'm also interested in
picking up 1-3 people that would like a mentor. Yeah, like the whole 'old
school' idea of a mentor. It's mainly so I can get some direct feedback
personally from newbies so I can determine what other people (besides me
and the other people I normally conspire with) are curious about, and
interested in. Email me at kynik@gh0st.net with a blurb about what you are
interested in, and why you want a mentor. And please, no ass-kissing
bullshit emails. Tell it like it is, and everyone's happier.

*** Ramblings : ajax

You'll see comments embedded in the articles within square brackets.
These are intentional, although they should not be treated as the article
author's content. The name in curly brackets indicates the commentator,

If you're thinking about submitting an article, but don't want us tagging
your masterpiece with our incoherent ramblings, that's cool, just let us

*** Random good URLs : Kynik, Ajax

Linux Security Audit FAQ:

Linux on Alpha systems:

Got a VAX lying around? Free Hobbyist Licenses for OpenVMS:

The sci.electronics.repair Links/FAQ Page:

Several good security papers:

Transparent Cryptographic File System:

*** The gh0st.net Project (Part 2 of 2): Phatal

<...continued from last issue>

[ The referenced graphics can soon be found on the following page in JPG
format. (http://fire.gh0st.net/napalm) {kynik} ]

Basic Network Structure:
Ok, here's what we've all been waiting for. This is what I've come up
with so far in terms of the structure of the network. I'll show you both
my initial plans for gh0stnet and the revised plans. As always, let the
suggestions, reprimands, and warnings fly. As we all know, the forum is
open, so any and everything is up for discussion. Here we go:


Initially, I planned on gh0stnet being located on one single physical
network so a bit of the design reflects that. Currently, in realizing
that there is no conceivable way for me to run 20 (and in the future >20)
systems at one time I've been considering some secure VPN solution...any
suggestions or comments about that one? Lemme know. The initial design of
gh0stnet is gh0st1.jpg. This is the original concept circa '94. When
developing the network then, I had very little knowledge about network
components and how they were set up, so you'll notice the scant detail and
the technical inaccuracy. Eventually, the initial idea evolved as I
learned more about network design. The concept is the important aspect
though so there are a few things to note.

[ although a gh0st.net compound would be a dream. {ajax} ]

1. Multiplicity - Multiple networks is an important part of the design.
Primarily because it is then possible for us to have fun with network
trust relations, loose firewalls, rogue routers, so on and so forth.

[ maybe some remote nodes from other groups on the VPN? {ajax} ]

2. Difficulty - You may not have noticed, but those black bars are
supposed to be firewalls...I know, my illustrations suck. I figured
the establishment of security domains like this (networks that don't
trust each other and embody disparate and at times conflicting
security policy) would be important. The difficulty is a major
factor, I really didn't want the whole thing to be easy...and I
didn't really want the entire thing to be difficult. So: levels of
difficulty. Plain and simple. This diagram doesn't really reflect
that very much, the current design emphasizes this though.

3. Heterogeneous - In considering the network would be difficult, I
assumed that difficulty would lay in unpredictability. Oddball
machines, Operating Systems, filtering rules, hacked up software and
other interesting tidbits would keep people guessing. Back then, my
concept of what was "oddball" is rather tame compared to what I have
in store now. In short, gh0stnet would be so obscure that users would
have to do multiple network scans... just to make sure they weren't
seeing things. I wanted every machine on the network to be so
interesting that figuring out what it did would be more engaging than
actually gaining root on the machine. Well, that's the ideal anyway.

[ different platforms lend themselves to different things. having our
own, custom software on each machine for people to play with would add
to the non-root-related interest. {ajax} ]

Ok, so those were the initial intentions/ideals. Among other initial
ideas was the inclusion of content on the servers. What kind of content?
Basically rare and pilfered information found in the darkest depths of
the ether. This is an idea I'd rather give some critical thought before I
even begin to conceptualize further... it's a bit dangerous. On the other
hand, throwing content having to deal with some of the internetworkings
of gh0stnet on the servers (such as information on versions of software,
type of hardware, and functions of boxen) wouldn't be such a bad idea. It
might fuel incentive.

New Design

Now, my current design of gh0stnet can be found in gh0st2.jpg. This
is much more of an end-view of the project rather than what it will start
out as. When examining the diagram, keep in mind that this is what I'm
working towards. This will be gh0stnet in all it's glory. I'll explain a
few of the aspects to take note of:

1. Infrastructure vs. Game - Differentiation between what we'll be using
as hunt and what we'll be using as infrastructure is important. The
nature of gh0stnet insists that we protect the outside world from
what goes on inside of the network. In this diagram, RouterX,
Firewall-A, and WWW are infrastructure.

WWW doesn't neccessarily have to be connected to gh0st.net but is used
as a way of communicating with the public. Both as a method of relaying
happenings on gh0st.net (logs, downed boxen, the idiot of the week) and
updates (limited network modification info).

[ Or hints, tricks and false leads... {kynik} ]

RouterX is important simply as a means of keeping gh0stnet up. It can't
be flooded and the routing rules shouldn't be modified. It should sit
there and route packets as it was meant to. This all pretty much goes
without saying, but being that we may not all neccessarily have the same
equipment, it's important that we make sure what we're running is up to
date and as secure as can possibly be.

Firewall-A must be up at all times. The rules should reflect something
like this: send in whatever you want, but nothing gets out. Although
we've already stated in the policy that malicious attacks on other
machines from gh0st.net boxes are prohibited, I'd like to make sure that
they simply don't happen. As a configuration, I'd like firewall-a to be
absolutely invisible, it should in no way appear to be a box available
for attack. The alternative is a rock-solid OS (can anyone say
"OPENBSD"?) that will be updated on a regular basis and function as a
kick-all-ass-don't-fuck-with-me firewall. Any suggestions or other

[ what you really want here is an ethernet bridge, hacked to filter
traffic. drop it in line between the internet connection and the hub.
it won't even show up on a traceroute; it doesn't even need to have an
ip address. i know this can be done in linux, although as phatal says,
openbsd would be better to trust for this. {ajax} ]

2. Difficulty Levels - In this diagram, I expanded on the original design
by creating 'tiers'. Ideally, each tier should be more difficult than
the one before it. My philosophy on this isn't really set in stone
and I've been fluctuating between providing a mixed bag..but
ultimately I'd like to have one network that would be damn near
impossible to penetrate. Any feelings on this one? I was playing
around with the idea the access to a higher tier should be dependent
on having successful defeated security on the tier directly below it.
Should users know how many tiers there are? Let me know what you

[ sounds like a video game ;). it does sound cool, though.
bridges, as above, don't require massive hardware - 40$ 486's should do
the job - and you might use them to completely hide segments of the
network from each other. you could even have all the bridges covertly
communicating with each other to enforce some very interesting dynamic
rulesets. this, combined with multiple protocol stacks (decnet,
appletalk, banyan, ipx...) could make life very interesting. {ajax} ]

3. What is Game? - Game is anything that can be connected to a network
and provides some form of entertainment. From either a security
standpoint or just a "Jesus christ..I can't beleive they actually
*hooked* that up to a network!" standpoint. KP2 is working on writing
a stack for the Apple //e, and the blue linux project seems to be a
good candidate for going up on the network. I have a TCP stack for
the Atari2600 written and ready to go...now I need to go out and buy
a new atari...mine was destroyed in the move :/. We can all get
together and make a list of the type of things we'd like to see on
the network. I currently have a list of OSs that are in my possession
that I thought would be good for certain tiers and I'll be
circulating that around to you folks ASAP.

[ blue linux and ataris... man, and i thought the layers-of-complexity
thing raised the video game quotient ;) {ajax} ]

Wrap Up and Further Direction

That pretty much wraps it up for right now. I just want to make sure
we're all on the same page and we're moving in similar directions. First
orders of business are basically getting the tiers up in *any* form
possible. I just want to start offering people boxes to crack. KP2 seems
to have some good space available so hopefully that will be the landmark
setup. In the mean time, consider available solutions, bumps in the
road, or discrepancies in these designs. This can be a reality, it's just
going to take a lot of work and a lot of dough... and some thinking...
we'll try to balance that off with large amounts of alcohol.



*** Quantum Cryptography: Kynik

It will happen eventually. Somebody will figure out a way to factor
large prime numbers, and, if you didn't know already, will break a decent
number of the 'military-grade' cryptographic algorithms out there today.
Are you using PGP to encrypt your email? Most likely your email wouldn't
be as secure as you'd hoped anymore, since RSA will be essentially broken.
What's the solution to this? Sure, you can make the keys bigger, but once
the mathematical holy grail of large number factoring is figured out,
that's a trivial obstacle.

So, what other way is there to encrypt a bunch of information? Well,
since 1984 or so, scientists have been working on a theoretically
unbreakable algorithm, and this field of science is called quantum
cryptography. It uses the principles of quantum physics (specifically, the
way photons-the smallest pieces of light-interact) to send a stream of
data securely between two points. A good article recently put out by New
Scientist gives a rather thorough explanation on how it works, and it is
from that article where I got the inspiration to write this blurb, as well
as a good deal of my information.


If you're looking for some more in-depth academic papers on the topic:


The underlying cryptographic technique used by quantum cryptography is
the elusive one-time pad algorithm, which is proven to be uncrackable. The
reason it's uncrackable, is because the key used to encrypt the message is
itself as long as the message. So, if I have the message:


I could make up a random string of the same length, like:


And encrypt (probably just XOR) the message with this string, creating an
unintelligible mess. Then, the person receiving the message would be able
to retrieve the original message by decrypting with the same string. Brute
forcing doesn't work against the one-time pad, since you could guess many
many wrong keys, and still never be sure if the message you received at
the end was correct. I could just as easily get:


And never be the wiser that I was mistaken. The big problem is that in
order for our target to be able to receive this message, we must figure
out a way to transmit the key to them securely, which we can't do. (Sure,
you could encrypt this key, but you would then be dependent on the
security of that algorithm)

This is where the 'quantum' part of quantum cryptography comes in. The
secret key is sent to the intended destination, with very low chance of
eavesdropping. Clear your minds, it's probably not something you've
thought of before, unless you've been working in quantum physics lately,
in which case, send me an email :)

[ I was just informed by TF that quantum cryptography is also mentioned in
Bruce Schneier's "Applied Cryptography", which I'd recommend to anyone
even remotely interested in cryptography, which means (in my mind) pretty
much everyone. {kynik} ]

Every photon of light has a polarity, which basically means the angle
that its wave moves in. for example, one photon may have a vertical
polarity, so it could roughly be depicted as such: | This photon has a
certain up-and-down motion as it travels. Another photon may have a
horizontal polarity, like so: - This photon moves back-and-forth as it
moves. Other photons can have any angle conceivable in between, two more
examples being 45 degree angles: / \ (Depicting this in text doesn't do
it any justice) Most light is a jumbled combination of all different
polarities, which I won't get into now. Polarized sunglasses, for
example, will only allow light of a certain polarity (well, a small set of
them, at least) to pass through the glass. Quantum crypto uses a very
high-quality polarizing filter to send and receive messages, where each
photon represents a single bit of the key being transmitted.

So, the sender sends out a stream of data, like so:

1 0 1 0 1 1 1 0

The sender changes this data into polarized photons, like so:

/ | / | / / / |

The receiver has similar filters on his side, which he randomly switches

\ - \ \ - \ - -

From New Scientist:

A photon striking a filter oriented in the same direction will always
pass through. Conversely, a photon striking a filter oriented
perpendicularly will never pass through. But a photon hitting a filter
that is diagonal to its own orientation is in a quantum quandary,
with a 50:50 chance of passing through or being blocked.

So if the sender sends a | photon, and the reveiver uses a - filter, there
is no way the photon would get through. However, if the receiver uses a \
filter, he has a one in two chance of receiving the photon. So, the
message the receiver gets might look something like this:

Data sent: 1 0 1 0 1 1 1 0
Filters: / | / | / / / |

Receiver: \ - \ \ - \ - -
Result: N N N Y N N Y N

Key: - - - 0 - - 1 -

The first three photons did not pass through, since they were
perpendicular, and would never pass through. The fourth did pass through.
The fifth lost the probability game and was not passed through. The sixth
and last were blocked for the same reason as the first three. The seventh
passed through for the same reason as the fourth, which is because it won
the coin toss and got passed.

The receiver (after enough bits had been sent) would then tell the
sender which bits he received, at which point the passed photons build
the key. In this case, the receiver tells the sender that the fourth and
the seventh bits were transmitted properly, but does not reveal the

You're probably pretty confused right now. I know I was the first three
or four times I read the New Scientist article. Something that may have
occurred to you is eavesdropping. This system is designed to minimize the
possibility of eavesdropping. Since there is only a 50 percent chance that
an eavesdropper would use the same filter as the receiver, and even if the
eavesdropper did, he would still only have a 50 percent chance of picking
up a "properly aligned" photon. The probability that an eavesdropper would
be able to pick any significant set of the photons that the receiver got
is very very small. I neglected to mention the fact that even if the
eavesdropper got every photon, that person could not be sure what the
sender's polarity is, so would have a hard time propagating an identical
message to the receiver.

Whoah. Quite a mouthful. I'm sure I've missed something, but this issue
is far too late and too long already. Go check out the New Scientist
article, and for MTYPWTK (More Than You Probably Wanted To Know), check
out some of the referenced research papers. I'm on a research paper kick
lately, so I blew through one in a few hours. Feel free to email me with
questions or things I should have made clearer.


*** Securing Your Communications (A Guide to VPNs): Prof_UK


A VPN (Virtual Private Network) is a secure connection between two or
more networks or computers over an untrusted network (for example the
Internet). A VPN can provide a much cheaper solution than a dedicated
direct network connection (such as a T1/E1).

There are many commercial solutions available for creating a VPN,
many of which use protocols like Microsoft's PPTP (Point to Point
Tunneling Protocol) and IPSec (others include L2PT and L2F). Firewall
products like Raptor's EagleNT Borderware and CheckPoint's Firewall 1
allow easy creation of a secure tunnel over the internet (but sometimes
using proprietary standards).

Creating a VPN using internet standards, without paying for extra
software, can be done within *nix. This can be done via a SSH tunnel or
IPSec. PPTP is quickly becoming more available on different formats
(Currently it is not as widespread on *nix as IPSec or SSH tunnels, but
its advantage is ease of use on Windows based machines).


Here we have two Linux firewalls, they each have two network adapters,
one for the outside connection and one for the internal connection.

------------ ------------
Network A ---|Firewall A|--> The Internet <-- |Firewall B|--- Network B
------------ ------------

* I have called the routers Firewall A and B as a VPN would often be
implemented through them as they provide a secure point on a network.

If someone on Network A wanted to email information to Company B it
leaves their secured network, goes across the internet and back into
Company B's network. The message wasn't encrypted and if the mail
contained sensitive information, like a username and password, it could
have been compromised.

So what is required is either a secure mail gateway, that encrypts all
mail destined for Network B (and vice versa) or we could set up a VPN,
where any traffic, whether it is Mail, Telnet or HTTP, is encrypted.

------------ ------------
Network A ---|Firewall A|--> The Internet <--|Firewall B|--- Network B
-----------\ /-----------
--> Encrypted A-B <--


SSH Tunnel

A SSH tunnel is quite easy to set up and it is quite well documented
in the Linux mini VPN HOW-TO:


This is a SSH (http://www.ssh.fi/) tunnel across the internet that the
two machines create and route traffic through. This method is cheap,
requires a little networking knowledge and has been used by many Linux
users around the world. It is also quite possible to have an
individual's machine on a VPN and connected to the internet at the same
time over a dial-up connection.

I believe that this method doesn't require vast amounts of computing
power which would allow multiple SSH tunnels to be created, but this is
not as easy as some of the other methods, as each tunnel would require
its own account on the machines.

The SSH tunnel can be made very secure (it is the second most secure
method mentioned here), with a RSA key (that can be up to 4096 bits),
for user verification and an encryption standard of your choice for
data transfers (IDEA, 3DES, Blowfish). SSH is widely available and even
with my windows client (TeraTermPro + TeraTerm Secure Shell Extension)
I have basic routing through the SSH connection.

IPSec is a secure version of IP, encrypting your data at OSI
level 3 (the network level). Actually it is an IPSec packet encapsulated
within IP. IPSec offers similar benefits of SSH tunneling (and more),
except it is implemented at the Kernel level. The easiest and cheapest
distribution (it's free) for Linux that I have found is FreeS/WAN.
(http://www.xs4all.nl/~freeswan/). Microsoft has placed IPSec support in
Windows 2000, OpenBSD also has IPSec support built in.

It is easy and quite flexible. It is basically a Kernel patch and a
few utilities, setup from within config files. One disadvantage is that
you will need to know the address of the first router on your
ISP/Network (this can normally be found with a traceroute). Setting up
multiple connections is easy, with a config file for each. The
documentation is quite good, although somestimes it is a little
obscure. FreeS/WAN supports IP masquerading, Subnet Extrusion and
Unencrypted tunnels.

FreeS/WAN is not yet a fully ICSA-certified IPSec implemenation but it
is interoperable with other available implementations. It supports IKE
(Internet Key Exchange) through Pluto (a small daemon). IKE makes the
creation and transportation of your keys secure and simple, allowing
your keys to be changed automatically. It also allows rekeying during a
connection, so if someone cracks your key, then they only get a small
part of your traffic (although that could still prove to be devastating).

This IPSec implementation supports MD5 (128bit) authentication and
3DES (168bit) encryption, with added support for SHA (160bit)

A Microsoft developed standard, it supports IP, IPX and NetBEUI. It
comes as standard in Microsoft NT4 server and workstation, it is also
available for Win95 and Win98 for free. The source code is available to
"third party developers." Like the IPSec protocol it is encapsulated
within IP packets, that is why it can carry IP, IPX and NetBEUI traffic.

If you wish to have single users connected to a NT Server then this is
the way to go, but how many people believe in the security in NT?

Clients are available from Microsoft for Win9x, but anything else must
come from a third party, there are clients available for Linux and more
are being released, but many belive that PPTP has lost to IPSec.

The standard uses Microsoft PAP and CHAP, within CHAP it supports,
wait for it, MD4 hashing and DES for authentication. The data
encryption is either RSA-RC4, (a full 40 bits, WOW Microsoft, real
secure) or 128bit. Making it the least secure method listed here. I
could only recommend this if you are un-comfortable with Linux or you
already have a highly integrated NT system.

[ actually, ms-pptp is slightly different from the pptp standard
(ftp://ftp.ietf.org/rfc/rfc2637.txt). the pap and chap
implementations in ms-pptp are also non-standard. pptp has been
shredded by mudge and schneier (www.counterpane.com/pptp.html), and
multiple vulnerabilities have been found by aleph one, among others.
avoid. i mean it. {ajax} ]

The Final Word

IPSec and SSH tunnels are currently the only solutions that I would
recommend. In the near future watch out for IPSec as a very popular
standard, supported within hardware etc. (Hell even Microsoft are
supporting it in their next version of NT). Within the project I am
involved in (Gh0st.net) we will be using a mixture of these methods,
depending on the situation (ie. The OS, availability of software etc.)

I should also mention that by having a VPN you are increasing the risk
of an "insider" attack, as you are basically giving all the users on
the other network the same access as your users. You should keep in
mind that even if you have an acceptable use policy in place, they
might not. It is a good idea to set up some simple protective measures
on your firewall to reduce the risk of such attacks.

[ you are also still at the mercy of the intermediary routers between
the firewalls to deliver the traffic intact and consistantly. the
only real cure for that is a dedicated connection, which is exactly
what VPNs are designed to replace. note also that VPNs are no
substitute for encrypted channels at the protocol level; just because
you're using IPSec doesn't mean you can go back to rsh. {ajax} ]

Within the next 2 - 3 years we should see IPv6 come along. This has
built in support for encryption, making things like IPSec obsolete. I
am looking forward to IPv6, but it is believed that as a large part of
the encryption key has been chosen/approved by the NSA to make it easy
for them to crack it. An extra layer of security over the top provided
by its users should be enough to keep the spooks at bay.

If you are serious about your security you should look closly at these
methods. You should be using SSH for any shell account, especially
those that contain sensitive communications.


Linux Mini VPN HowTo
FreeS/WAN documentation.
Microsoft PPTP documentation.
Various others.

A Gh0st.net text - Published with Authors permission
Gh0st.net - The Ultim8 Security Concept
Send us your spare hardware !!! please...

*** Future Issues

Securing X : Ajax
Creating Restricted ("Sandboxed") User Accounts : Fict

Other articles : c_routine
: echo8

*** Credits

Editor: Kynik <kynik@gh0st.net>
Co-editor: ajax <ajax@gh0st.net>
Article Contributions: Phatal <phatal@gh0st.net>
Prof_UK <prof_uk@gh0st.net>

*** Subscription

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