Harvard University, Kennedy School of Government
Information Infrastructure Project
Symposium on the Global Information Infrastructure:
Information, Policy & International Infrastructure
Cambridge, MA, January 28-30, 1996
Risk-Free Access Into The
Global Information Infrastructure
Via Anonymous Re-Mailers
by Paul A. Strassmann, US Military Academy, West Point; and Senior Advisor,
SAIC
and William Marlow, Senior Vice President, Science Applications
International Corporation (SAIC)
Quoted portions are excerpted from Raph Levien's Remailer List.
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The Context
By far the greatest threat to the commercial, economic and political
viability of the Global Information Infrastructure will come from
information terrorists. Information terrorism has ceased to be an
amateur effort and has migrated into the hands of well organized,
highly trained expert professionals. Information terrorist attacks can
be expected to become a decisive element of any combined threat to the
economic and social integrity of the international community. Nations
whose life-line becomes increasingly dependent on information networks
should realize that there is no sanctuary from information-based
assaults. Commercial organizations, especially in telecommunications,
finance, transportation and power generation offer choice targets to
massive disruption.
Information terrorism, as a particularly virulent form of information
warfare, is a unique phenomenon in the history of warfare and crime.
For the last two hundred years the theory of warfare has been guided by
"force-exchange" equations in which the outcome was determined by the
rate of attrition of each opposing force. In information attacks these
equations do not apply because the attacker remains hidden and cannot
be retaliated against.
Since biblical times, crimes have been deterred by the prospects of
punishment. For that, the criminal had to be apprehended. Yet
information crimes have the unique characteristic that apprehension is
impossible, since even identification of the criminal is not feasible.
Information crimes can be committed easily without leaving any telltale
evidence such as fingerprints, traces of poison or bullets.
Changes Introduced By Anonymous Re-Mailers
The introduction of Anonymous Re-mailers into the Internet has altered
the capacity to balance attack and counter-attack, or crime and
punishment. The widespread use and easy access to acquiring the
capacity to launch anonymous messages and software has so far not
received adequate attention from a policy and legal standpoint. This
topic is sufficiently technical that it has been largely avoided by
experts who have so far concentrated on debating social, legal,
political and economic consequences of the Global Information
Infrastructure. Yet, unless there is a thorough understanding of the
technologies that make the Anonymous Re-mailers sources of a
pathological danger, there is little hope that effective preventive
measures and safeguards can be put in place.
In many respects, the avoidance of technical discussions about some of
the pathological aspects of the Internet remind me of the state of
medical diagnosis prior to the recognition that bacteriology,
prophylactics and inoculation can be only applied following the
acceptance of rigorous, analytic and experimental disciplines.
Our Agenda
The purpose of this paper is to bring to the attention of policy-makers
some of the relevant facts about Anonymous Re-mailers. All of the
material quoted here comes from public sources which are easily
accessible to anyone. The wide-spread current uses of Anonymous
Re-mailers should be sufficient warning that this topic cannot be
considered any more as something hidden, confidential or inappropriate
for public discussion.
We find many similarities in the initial denials to the threats from
AIDS by the medical and public health establishment. We are dismayed by
the avoidance of a candid assessment by public officials about the
vulnerability of the Global Information Infrastructure to destructive
information epidemics. The purpose of this paper is to increase the
awareness of potentially deadly risks that may inhibit the potential
gains from the creation of a global information community.
What Is A Re-Mailer?
A re-mailer allows anyone to post messages to newsgroups or to
individuals while remaining anonymous. The identity of the sender is
hidden from the recipient and remains practically untraceable.
An anonymous re-mailer is a program that runs on a computer somewhere
on the Internet. When you send mail to the re-mailer address, the
re-mailer takes your name and your address off of the mail message and
forwards it to its next destination. The recipient gets mail that has
no evidence of where it originally came from, at least not in the
headers. You might give away your secret identity in the body of the
message, but that would be the sender's own fault.
Anonymous re-mailers can be "chained" so that a message is passed on
from one anonymous re-mailer to another, in two or more separate
anonymous "hops" as a way of making physical tracing or monitoring
increasingly difficult.
One of the most prominent anonymous re-mailers is <anon.penet.fi> is in
Finland. It is frequently used by the Russian (ex-KGB) criminal
element. <Anon.penet.fi> assigns a numeric identification to each
address from which it receives mail. Internet recipients can reply to
that secret number. <anon.penet.fi> will also assign to them another
anonymous number, and then forward the reply. This creates a
double-blind situation where two people could have an ongoing exchange
and never know who the other person was. This method of communication
is favorite for engaging services of cybercriminals and for authorizing
payment for their acts through a third party.
<Anon.penet.fi> can be also used to post a message to Usenet as well.
The message can be read by thousands of people, and anyone can send an
anonymous reply to the secret Finnish identity. The readers of this
paper can easily avail themselves of these services without any special
training. Detailed instructions for the use of a remailer service are
usually included in the "help" software posted in the remailer's files.
For example:
To get an anonymous re-mailer address follow the following
instruction. First, you should send mail to:
<help@anon.penet.fi>. You'll get back a nice help file
automatically. Next, send mail to <ping@anon.penet.fi>. This
will allocate your number--from now on you'll be something
like <anXXXXXX@anon.penet.fi>, where XXXXXX is your number.
Once you have received your anonymous address you can use it
like your normal e-mail address.
These capabilities are not trivial, but a source of an exhaustive body
of software and communications know-how which can be learned best by
consulting one of the many tutorials about this topic, such
as<ftp.csua.berkeley.edu:
/pub/cypherpunks/re-mailer/hal's.remailer.gz>:
Cyberpunk re-mailers allow a person to send mail with no trace of
identity. To use a re-mailer simply do the following:
* Add the header Request-Remailing-To: and sending to one of the
addresses listed below. These headers must be typed in exactly.
Mail without these headers is either rejected or delivered to the
re-mailer administrators.
* If you cannot add the required headers, place two colons (::) on
the very first line of your message, then on the next line type
Request-Remailing-To: and the address you want to send anonymously
to.
* Skip a line, and then begin the message. By using this method you
can send the message through more than one re-mailer which will
certainly ensure that it will be anonymous.
* Many re-mailers only allow one recipient per message. A number of
standard Cyberpunk Re-mailers are available.
There is a wealth of easily accessible step-by-step instructional
material available on the Internet how to use re-mailers and how to
evade countermeasures or possibility of detection from any source.
Re-mailer operators are in frequent contact with each other and exhibit
many of the fraternal habits that previously were shared between
amateur radio operators. Some of the most interesting sources of
information are:
André Bacard's anonymous re-mailer FAQ is an excellent nontechnical
introduction.
For a different take on Net anonymity, see L.Detweiler's home page.
Tools
* Private Idaho is an anonymous re-mailer utility for Windows,
supporting PGP, the cypherpunks re-mailers, and Mixmaster, and the
<alpha.c2.org> alias server. It too automatically configures
itself based on this re-mailer list.
* <ChainMail> is a re-mailer chaining utility for Mac users, by
Jonathan Rochkind. To use it, you need Eudora, MacPGP, and
applescript, in addition to a number of applescript scripting
additions.
* <Privtool> is a PGP-aware mailer that also supports Mixmaster.
* The Community ConneXion has put the Web-premail gateway on its SSL
server. That means that you can send anonymous email from the Web
without exposing your message in the clear on the connection
between your Web browser and the gateway.
* Sameer Parekh's NEXUS Berkeley / Community ConneXion has a web
page set up for sending anonymous mail from your Web client.
* Michael Hobbs has set up Web gateway to premail. Now you can send
anonymous email directly from your Web browser. Don't use this for
extremely sensitive stuff, though, because it isn't quite as
secure as running premail yourself (in particular, the connection
between your Web browser and the gateway is not encrypted).
* A good source for re-mailer information is the Anonymity,
re-mailers, and your privacy page compiled by "Galactus". This is
also the best place to look for information about anon.penet.fi.
* Matt Ghio's re-mailer list is available by fingering
re-mailer.help.all@chaos.taylored.com. This file also has all the
public keys for PGP-friendly re-mailers. Matt also has a pinging
service similar to this one, available by fingering
re-mailer-list@chaos.taylored.com.
* Chaos is having problems getting recognized on the Net. Try
re-mailer.help.all@204.95.228.28 and see if that works any better.
Newer information can be gotten by sending mail to
mg5n+re-mailers@andrew.cmu.edu.
* Help for the Alpha alias server (also available in a plain email
version. This is the best way to create an alias for anonymous
replies to mail. Not only is it the most cryptographically secure,
but you get to pick the alias nickname of your choice. The email
addresses are of the form <alias@alpha.c2.org>. Highly
recommended.
* Usura's home page has a bunch of re-mailer related stuff on it,
including a help page on chaining re-mailers.
* The Armadillo re-mailer now has its own Web page.
* Crown re-mailer help and statistics.
* Ecafe re-mailer has its own Web page, including quickie info about
how to use the re-mailer without encryption or any other extras.
Other resources
* You want to send secure mail to someone, but don't know their key.
Where are you going to get it? Try the keyserver at MIT.
* Vince Cate's Cryptorebel and Cypherpunk page has pointers to lots
of cypherpunk resources.
* John Perry's jpunix page has info on his MX service for hidden
re-mailers, as well as cool links for Mixmaster and other stuff.
* Lance Cottrell's home page, which has his Chain script, the
Mixmaster re-mailer client (including Sun binaries!) as well as
other cypberpunk related topics.
* Vince Gambino's re-mailer page has a good collection of re-mailer
help files.
Where Do You Find Re-Mailers?
Computers that offer remailing capabilities are operated by individuals
or organizations as a public service, almost always at no charge
because it costs so little to set one up. They are available globally.
We offer a partial list of re-mailers:
$remailer{"extropia"} = "<remail@extropia.wimsey.com> cpunk
pgp special";
$remailer{"portal"} = "<hfinney@shell.portal.com> cpunk pgp
hash";
$remailer{"alumni"} = "<hal@alumni.caltech.edu> cpunk pgp
hash";
$remailer{"bsu-cs"} = "<nowhere@bsu-cs.bsu.edu> cpunk hash
ksub";
$remailer{"c2"} = "<remail@c2.org> eric pgp hash reord";
$remailer{"penet"} = "<anon@anon.penet.fi> penet post";
$remailer{"ideath"} = "<remailer@ideath.goldenbear.com> cpunk
hash ksub reord";
$remailer{"hacktic"} = "<remailer@utopia.hacktic.nl> cpunk
mix pgp hash latent cut post ek";
$remailer{"flame"} = "<remailer@flame.alias.net> cpunk mix
pgp. hash latent cut post ek reord";
$remailer{"rahul"} = "<homer@rahul.net> cpunk pgp hash
filter";
$remailer{"mix"} = "<mixmaster@remail.obscura.com> cpunk mix
pgp hash latent cut ek ksub reord ?";
$remailer{"syrinx"} = "<syrinx@c2.org> cpunk pgp hash cut
reord mix post";
$remailer{"ford"} = "<remailer@bi-node.zerberus.de> cpunk pgp
hash ksub";
$remailer{"hroller"} = "<hroller@c2.org> cpunk pgp hash
latent ek";
$remailer{"vishnu"} = "<mixmaster@vishnu.alias.net> cpunk mix
pgp. hash latent cut ek ksub reord";
$remailer{"robo"} = "<robo@c2.org> cpunk hash mix";
$remailer{"replay"} = "<remailer@replay.com> cpunk mix pgp
hash latent cut post ek";
$remailer{"spook"} = "<remailer@valhalla.phoenix.net> cpunk
mix pgp hash latent cut ek reord";
$remailer{"rmadillo"} = "<remailer@armadillo.com> mix cpunk
pgp hash latent cut";
$remailer{"ecafe"} = "<cpunk@remail.ecafe.org> cpunk mix";
$remailer{"wmono"} = "<wmono@valhalla.phoenix.net> cpunk mix
pgp. hash latent cut ek";
$remailer{"shinobi"} = "<remailer@shinobi.alias.net> cpunk
mix hash latent cut ek reorder";
$remailer{"amnesia"} = "<amnesia@chardos.connix.com> cpunk
mix pgp hash latent cut ek ksub";
$remailer{"gondolin"} = "<mix@remail.gondolin.org> cpunk mix
pgp hash latent cut ek reord";
$remailer{'alpha'} = '<alias@alpha.c2.org> alpha pgp';
$remailer{'gondonym'} = '<alias@nym.gondolin.org> alpha pgp';
Much of the knowledge about the characteristics of these
re-mailers is available from
<remailer-list@kiwi.cs.berkeley.edu>
Role Of Encryption
For added protection, users of Anonymous Re-mailers tend to encrypt
their messages just in case one of the remailing links are compromised.
PGP (Pretty Good Privacy) encryption is favored because it is freely
available and easy to use. A typical digital signature would look like
this:
-----BEGIN PGP SIGNATURE-----
Version: 2.6.2
iQCVAwUBMPDy4WV5hLjHqWbdAQEqYwQAm+o313Cm2ebAsMiPIwmd1WwnkPXEaYe9
pGR5ja8BKSZQi4TAEQOQwQJaghI8QqZFdcctVYLm569I1/8ah0qyJ+4fOfUiAMda
Sa2nvJR7pnr6EXrUFe1QoSauCASP/QRYcKgB5vaaOOuxyXnQfdK39AqaKy8lPYbw
MfUiYaMREu4=
=9CJW
-----END PGP SIGNATURE-----
For responses the sender will choose a passphrase. This phrase will be
used to encrypt messages sent back to you. The encryption will be
single-key encryption, not PGP's normal public-private key encryption.
The reason for this is that public key encryption is usually not
necessary in such cases. Single-key encryption does not require a
database (such as in the widely used <anon.penet.fi> database for
mapping aliases onto addresses), thus increasing the security of
communications among anonymous users.
When a recipient responds to the e-mail, his response will be encrypted
with the sender's pass-phrase. The sender can read the response by
saving it to a file and using PGP on it. PGP will ask for the
passphrase, enter the sender's reply, which will make it possible for
the recipient to see the response to the e-mail. This feature allows
both parties to be securely encrypted, protecting privacy and anonymity
in both directions.
How Reliable Are The Re-Mailers?
The knowledge about the characteristics, reliability and
trustworthiness of re-mailers is widely distributed through various
bulletin boards. These are consulted by persons deeply immersed in
Internet-related developments. There is an agile and very active global
community that keeps track of the average latency time, uptime of
frequently used re-mailers. They post their findings, which in many
cases is superior to what a commercial customer is likely to find out
about their own data center performance, or about the service quality
offered by Compuserve, America-On-Line of Prodigy. Here is an excerpt
from such a bulletin:
hacktic remailer@utopia.hacktic.nl **** ******* 7:10 99.85%
c2 remail@c2.org -.-++ ++-.-+ 2:10:42 99.83%
rmadillo remailer@armadillo.com +++++ ++++++ 37:03 99.69%
flame remailer@flame.alias.net ** * ******* 14:55 99.64%
mix mixmaster@remail.obscura.com _ _-__...-++ 17:40:48 99.21%
amnesia amnesia@chardos.connix.com -+ +--+--- 2:04:43 99.20%
ecafe cpunk@remail.ecafe.org ## ##-## #-- 1:26:54 99.06%
extropia remail@extropia.wimsey.com .- -.----_. 13:48:11 99.04%
replay remailer@replay.com + +** ***** 5:36 98.84%
shinobi remailer@shinobi.alias.net -- -- - - + 54:43 98.78%
spook remailer@valhalla.phoenix.net * ***** - * 35:07 98.36%
vishnu mixmaster@vishnu.alias.net ** #-*# 7:44 98.20%
bsu-cs nowhere@bsu-cs.bsu.edu # # ##.# 28:07 97.78%
gondolin mix@remail.gondolin.org - --_.---- 9:45:55 97.62%
wmono wmono@valhalla.phoenix.net ** * * 12:23 97.57%
hroller hroller@c2.org #*+### -.. # 1:37:24 96.71%
ford remailer@bi-node.zerberus.de ._...--._. 21:21:22 95.83%
portal hfinney@shell.portal.com ########*# 27:36 95.55%
alumni hal@alumni.caltech.edu # # * + 25:47 95.29%
penet anon@anon.penet.fi . -- -- 13:55:20 87.78%
rahul homer@rahul.net +* *+**+* # 4:34 93.71%
robo robo@c2.org #-## 5:59 27.86%
History key
# response in less than 5 minutes.
* response in less than 1 hour.
+ response in less than 4 hours.
- response in less than 24 hours.
. response in less than 2 days.
Specialization Of Services
The operators of various re-mailers are specialized in that they cater
to select communities of Internet dwellers. They offer unique services
to customers who are seeking different degrees of anonymity.
Cognoscenti in the field can readily identify remailers who offer meets
diffferent tastes and preferences. Here is an example of remailer
characterizations:
<cpunk> A major class of remailers. Supports
Request-Remailing-To: field.
<eric> A variant of the cpunk style. Uses Anon-Send-To:
instead.
<penet> The third class of remailers (at least for right
now). Uses X-Anon-To: in the header.
<pgp> Remailer supports encryption with PGP. A period after
the keyword means that the short name, rather than the full
email address, should be used as the encryption key ID.
<hash> Supports ## pasting, so anything can be put into the
headers of outgoing messages.
<ksub> Re-mailer always kills subject header, even in non-pgp
mode.
<nsub> Re-mailer always preserves subject header, even in pgp
mode.
<latent> Supports Matt Ghio's Latent-Time: option.
<cut> Supports Matt Ghio's Cutmarks: option.
<post> Post to Usenet using Post-To: or Anon-Post-To: header.
<ek> Encrypt responses in reply blocks using Encrypt-Key:
header.
<special> Accepts only pgp encrypted messages.
<mix> Can accept messages in Mixmaster format.
<reord> Claims to foil traffic analysis by reordering
messages.
<mon> Re-mailer has been known to monitor contents of private
email.
<filter> Re-mailer has been known to filter messages based on
content. If not listed in conjunction with <mon>, then only
messages destined for public
<alpha> Supports nyms according to the protocol used by
alpha.c2.org. This list will be featuring reliability and
latency measurements soon for these nymservers.
A fascinating example of specialization is a re-mailer service
advertising the capacity to defeat "traffic analysis" used by
intelligence agencies. All mail to each destination is first sent
through <remail@sitename> which is a standard "cypherpunk" re-mailer
with PGP with a few added features. The outgoing mail is not forwarded
immediately upon receipt. Outgoing messages are stored in a pool until
five minutes after each hour, when all messages in the pool are
re-transmitted in a random order, ignoring the order in which they came
in. Each message from the re-mailer is sent through a random path of
other re-mailers in the re-mailernet. This usually involves between
five to 20 "hops" from one re-mailer to another. In each case care is
taken for at least one of the "hops" to be in a country with especially
relaxed laws concerning electronic messages. Such measures would
greatly complicate any tracing that may be contemplated by a
law-enforcement agency.
Why Re-Mailers?
E-mail is as fast and casual as a voice phone call, but can be stored
and retrieved with infinitely greater efficiency than paper letters or
taped conversations. An e-mail message can be re-broadcast the world
over, by anyone who comes across a copy of the transmission. Parts of
any message can be extracted, edited and easily modified. Meanwhile,
the e-mail address of the originator remains a label of its origin. If
the storage of that message is not protected - and it rarely is - it
can be accessed by anyone who takes the trouble to rummage through any
of the many archived computer records that may have received such
message. A casual e-mail exchange, with an identifying address, can be
then used to compromise the originator. As e-mail traffic takes over an
ever increasing share of personal communications, inspection of e-mail
traffic can yield more comprehensive evidence than just about any
wire-tapping efforts. E-mail-tapping is less expensive, more thorough
and less forgiving than any other means for monitoring personal
communications. Without protection of privacy, browsing through e-mail
archives would become the preferred way for gathering evidence in law
enforcement cases. It would also be used as the favorite means for
collecting incriminating statements by lawyers engaged in civil
litigation.
In casual e-mail exchanges it is easy to make an error. When the
message is archived it could be used to haunt a person for decades
afterwards. A message intended for a particular individual may be
passed on to hundreds or even thousands of others. Unless its origin is
anonymous, all e-mail can be traced through identifying addresses that
preserve the name of the originator - as well as the names of those who
forwarded it - wherever the message traversed. Unless a message is
handled anonymously, a trace is left about everyone who received it or
passed it on. It would be like a letter that not only identifies the
name and address of its author, but also fingerprints of anyone who
ever touched it.
It is one of the fundamental strengths of the Internet that it offers
an almost universal capacity for free expression of ideas. A person's
opinions can be sent anywhere in the world in a matter of minutes, with
the originator's name displayed at the top. Is it consistent with the
rights to individual privacy and freedom of expression to have one's
name clearly associated with a message than may be easily disseminated
to unintended recipients?
The issues here are the rights to the freedom of speech and to the
rights to personal privacy. Having the right to free speech may work
well in the case of verbal expression, but it may cease to have its
intended purpose in face of retaliation that may take place decades
later. In a system that theoretically can have infinitely large memory
and indefinitely long remembrance, the freedom of expression and become
abused and perverted by a government that does not respect individual
rights.
With the widespread acceptance of Internet-mediated communications it
was recognized that the simplest way of securing privacy is through
anonymity. That's how anonymous re-mailers came into being. Given the
technical characteristics of Internet, there is nothing to prevent
anyone to set up a private (or public) anonymous remailing service. Any
attempt to prohibit or regulate the use of anonymous re-mailers is
technically unfeasible. In a democratic society it becomes politically
unacceptable to suppress remailers as potential sources of criminal
acts. Such absolute prohibitions would never pass through a legislative
process in a free society.
Conclusion
Anonymous re-mailers are here to stay. Like in the case of many
virulent diseases, there is very little a free society can do to
prohibit travel or exposure to sources of infection. The best one can
do is to start treating the pathologies inherent in the Internet in the
same way as we have learned to deal with infectious epidemics. That
calls for constructing new institutions and processes that are
analogues to inoculation, immunization, prophylactics, clean water
supply, sewers, hygiene, early detection of outbreaks of diseases,
quarantine, the offices of health examiners, the Center of Disease
Control and the World Health Organization.
The introduction of most of these restrictive means, imposed mostly by
government, were often opposed by those who saw in public health
injunctions infringement of individual rights. In due course an
informed electorate found it expedient to accept most of the sanitary
measures for disease control a bargain that was well worth it.
The history of public health teaches us that suppression of any disease
must be preceded by a thorough understanding of its behavior, its
method of transmission and how it creates its own ecology. As in the
case of smallpox, yellow fever, flu epidemics, AIDS or malaria, it will
take disasters before the public may accept that some forms of
restrictions on the electronic freedom of speech and privacy may be
worthwhile.
It was the purpose of this paper to explain the characteristics of
anonymous remailers as one of the potential sources of infectious
threats to the well-being of our information-based civilization. We
trust that this will be seen as a useful contribution to an already
raging debate of how to find a balance between the desirable and the
dangerous.
Paul@Strassmann.com and William_Marlow@cpqm.saic.com will be pleased to
respond to identifiable commentators on the points of view expressed
herein.