From:	 Bruce Schneier <schneier@counterpane.com>
To:	 crypto-gram@chaparraltree.com
Subject: CRYPTO-GRAM SPECIAL ISSUE, September 30, 2001
Date:	 Sun, 30 Sep 2001 20:10:57 -0500

                  CRYPTO-GRAM

               September 30, 2001

               by Bruce Schneier
                Founder and CTO
       Counterpane Internet Security, Inc.
            schneier@counterpane.com
          <http://www.counterpane.com>


A free monthly newsletter providing summaries, analyses, insights, and 
commentaries on computer and network security.

Back issues are available at 
<http://www.counterpane.com/crypto-gram.html>.  To subscribe, visit 
<http://www.counterpane.com/crypto-gram.html> or send a blank message to 
crypto-gram-subscribe@chaparraltree.com.

Copyright (c) 2001 by Counterpane Internet Security, Inc.


** *** ***** ******* *********** *************

This is a special issue of Crypto-Gram, devoted to the September 11 
terrorist attacks and their aftermath.

Please distribute this issue widely.

In this issue:
      The Attacks
      Airline Security Regulations
      Biometrics in Airports
      Diagnosing Intelligence Failures
      Regulating Cryptography
      Terrorists and Steganography
      News
      Protecting Privacy and Liberty
      How to Help


** *** ***** ******* *********** *************

                 The Attacks



Watching the television on September 11, my primary reaction was amazement.

The attacks were amazing in their diabolicalness and audacity: to hijack 
fuel-laden commercial airliners and fly them into buildings, killing 
thousands of innocent civilians.  We'll probably never know if the 
attackers realized that the heat from the jet fuel would melt the steel 
supports and collapse the World Trade Center.  It seems probable that they 
placed advantageous trades on the world's stock markets just before the 
attack.  No one planned for an attack like this.  We like to think that 
human beings don't make plans like this.

I was impressed when al-Qaeda simultaneously bombed two American embassies 
in Africa.  I was more impressed when they blew a 40-foot hole in an 
American warship.  This attack makes those look like minor operations.

The attacks were amazing in their complexity.  Estimates are that the plan 
required about 50 people, at least 19 of them willing to die.  It required 
training.  It required logistical support.  It required coordination.  The 
sheer scope of the attack seems beyond the capability of a terrorist 
organization.

The attacks rewrote the hijacking rule book.  Responses to hijackings are 
built around this premise: get the plane on the ground so negotiations can 
begin.  That's obsolete now.

They rewrote the terrorism book, too.  Al-Qaeda invented a new type of 
attacker.  Historically, suicide bombers are young, single, fanatical, and 
have nothing to lose.  These people were older and more experienced.  They 
had marketable job skills.  They lived in the U.S.: watched television, ate 
fast food, drank in bars.  One left a wife and four children.

It was also a new type of attack.  One of the most difficult things about a 
terrorist operation is getting away.  This attack neatly solved that 
problem.  It also solved the technological problem.  The United States 
spends billions of dollars on remote-controlled precision-guided munitions; 
al-Qaeda just finds morons willing to fly planes into skyscrapers.

Finally, the attacks were amazing in their success.  They weren't 
perfect.  We know that 100% of the attempted hijackings were successful, 
and 75% of the hijacked planes successfully hit their targets.  We don't 
know how many planned hijackings were aborted for one reason or 
another.  What's most amazing is that the plan wasn't leaked.  No one 
successfully defected.  No one slipped up and gave the plan away.  Al-Qaeda 
had assets in the U.S. for months, and managed to keep the plan 
secret.  Often law enforcement has been lucky here; in this case we weren't.

Rarely do you see an attack that changes the world's conception of attack, 
as these terrorist attacks changed the world's conception of what a 
terrorist attack can do.  Nothing they did was novel, yet the attack was 
completely new.  And our conception of defense must change as well.


** *** ***** ******* *********** *************

        Airline Security Regulations



Computer security experts have a lot of expertise that can be applied to 
the real world.  First and foremost, we have well-developed senses of what 
security looks like.  We can tell the difference between real security and 
snake oil.  And the new airport security rules, put in place after 
September 11, look and smell a whole lot like snake oil.

All the warning signs are there: new and unproven security measures, no 
real threat analysis, unsubstantiated security claims.  The ban on cutting 
instruments is a perfect example.  It's a knee-jerk reaction: the 
terrorists used small knives and box cutters, so we must ban them.  And 
nail clippers, nail files, cigarette lighters, scissors (even small ones), 
tweezers, etc.  But why isn't anyone asking the real questions: what is the 
threat, and how does turning an airplane into a kindergarten classroom 
reduce the threat?  If the threat is hijacking, then the countermeasure 
doesn't protect against all the myriad of ways people can subdue the pilot 
and crew.  Hasn't anyone heard of karate?  Or broken bottles?  Think about 
hiding small blades inside luggage.  Or composite knives that don't show up 
on metal detectors.

Parked cars now must be 300 feet from airport gates.  Why?  What security 
problem does this solve?  Why doesn't the same problem imply that passenger 
drop-off and pick-up should also be that far away?  Curbside check-in has 
been eliminated.  What's the threat that this security measure has 
solved?  Why, if the new threat is hijacking, are we suddenly worried about 
bombs?

The rule limiting concourse access to ticketed passengers is another one 
that confuses me.  What exactly is the threat here?  Hijackers have to be 
on the planes they're trying to hijack to carry out their attack, so they 
have to have tickets.  And anyone can call Priceline.com and "name their 
own price" for concourse access.

Increased inspections -- of luggage, airplanes, airports -- seem like a 
good idea, although it's far from perfect.  The biggest problem here is 
that the inspectors are poorly paid and, for the most part, poorly educated 
and trained.  Other problems include the myriad ways to bypass the 
checkpoints -- numerous studies have found all sorts of violations -- and 
the impossibility of effectively inspecting everybody while maintaining the 
required throughput.  Unidentified armed guards on select flights is 
another mildly effective idea: it's a small deterrent, because you never 
know if one is on the flight you want to hijack.

Positive bag matching -- ensuring that a piece of luggage does not get 
loaded on the plane unless its owner boards the plane -- is actually a good 
security measure, but assumes that bombers have self-preservation as a 
guiding force.  It is completely useless against suicide bombers.

The worst security measure of them all is the photo ID requirement.  This 
solves no security problem I can think of.  It doesn't even identify 
people; any high school student can tell you how to get a fake ID.  The 
requirement for this invasive and ineffective security measure is secret; 
the FAA won't send you the written regulations if you ask.  Airlines are 
actually more stringent about this than the FAA requires, because the 
"security" measure solves a business problem for them.

The real point of photo ID requirements is to prevent people from reselling 
tickets.  Nonrefundable tickets used to be regularly advertised in the 
newspaper classifieds.  Ads would read something like "Round trip, Boston 
to Chicago, 11/22 - 11/30, female, $50."  Since the airlines didn't check 
ID but could notice gender, any female could buy the ticket and fly the 
route.  Now this doesn't work.  The airlines love this; they solved a 
problem of theirs, and got to blame the solution on FAA security requirements.

Airline security measures are primarily designed to give the appearance of 
good security rather than the actuality.  This makes sense, once you 
realize that the airlines' goal isn't so much to make the planes hard to 
hijack, as to make the passengers willing to fly.  Of course airlines would 
prefer it if all their flights were perfectly safe, but actual hijackings 
and bombings are rare events and they know it.

This is not to say that all airport security is useless, and that we'd be 
better off doing nothing.  All security measures have benefits, and all 
have costs: money, inconvenience, etc.  I would like to see some rational 
analysis of the costs and benefits, so we can get the most security for the 
resources we have.

One basic snake-oil warning sign is the use of self-invented security 
measures, instead of expert-analyzed and time-tested ones.  The closest the 
airlines have to experienced and expert analysis is El Al.  Since 1948 they 
have been operating in and out of the most heavily terroristic areas of the 
planet, with phenomenal success.  They implement some pretty heavy security 
measures.  One thing they do is have reinforced, locked doors between their 
airplanes' cockpit and the passenger section.  (Notice that this security 
measure is 1) expensive, and 2) not immediately perceptible to the 
passenger.)  Another thing they do is place all cargo in decompression 
chambers before takeoff, to trigger bombs set to sense altitude.  (Again, 
this is 1) expensive, and 2) imperceptible, so unattractive to American 
airlines.)  Some of the things El Al does are so intrusive as to be 
unconstitutional in the U.S., but they let you take your pocketknife on 
board with you.

Airline security:
<http://www.time.com/time/covers/1101010924/bsecurity.html>
<http://www.accessatlanta.com/ajc/terrorism/atlanta/0925gun.html>

FAA on new security rules:
<http://www.faa.gov/apa/faq/pr_faq.htm>

A report on the rules' effectiveness:
<http://www.boston.com/dailyglobe2/266/nation/Passengers_say_banned_items_ha 
ve_eluded_airport_monitors+.shtml>

El Al's security measures:
<http://news.excite.com/news/ap/010912/18/israel-safe-aviation>
<http://news.excite.com/news/r/010914/07/international-attack-israel-elal-dc>

More thoughts on this topic:
<http://slate.msn.com/HeyWait/01-09-17/HeyWait.asp>
<http://www.tnr.com/100101/easterbrook100101.html>
<http://www.tisc2001.com/newsletters/317.html>

Two secret FAA documents on photo ID requirement, in text and GIF:
<http://www.cs.berkeley.edu/~daw/faa/guid/guid.txt>
<http://www.cs.berkeley.edu/~daw/faa/guid/guid.html>
<http://www.cs.berkeley.edu/~daw/faa/id/id.txt>
<http://www.cs.berkeley.edu/~daw/faa/id/id.html>

Passenger profiling:
<http://www.latimes.com/news/nationworld/nation/la-091501profile.story>

A CATO Institute report: "The Cost of Antiterrorist Rhetoric," written well 
before September 11:
<http://www.cato.org/pubs/regulation/reg19n4e.html>

I don't know if this is a good idea, but at least someone is thinking about 
the problem:
<http://www.zdnet.com/anchordesk/stories/story/0,10738,2812283,00.html>


** *** ***** ******* *********** *************

             Biometrics in Airports



You have to admit, it sounds like a good idea.  Put cameras throughout 
airports and other public congregation areas, and have automatic 
face-recognition software continuously scan the crowd for suspected 
terrorists.  When the software finds one, it alerts the authorities, who 
swoop down and arrest the bastards.  Voila, we're safe once again.

Reality is a lot more complicated; it always is.  Biometrics is an 
effective authentication tool, and I've written about it before.  There are 
three basic kinds of authentication: something you know (password, PIN 
code, secret handshake), something you have (door key, physical ticket into 
a concert, signet ring), and something you are (biometrics).  Good security 
uses at least two different authentication types: an ATM card and a PIN 
code, computer access using both a password and a fingerprint reader, a 
security badge that includes a picture that a guard looks at.  Implemented 
properly, biometrics can be an effective part of an access control system.

I think it would be a great addition to airport security: identifying 
airline and airport personnel such as pilots, maintenance workers, 
etc.  That's a problem biometrics can help solve.  Using biometrics to pick 
terrorists out of crowds is a different kettle of fish.

In the first case (employee identification), the biometric system has a 
straightforward problem: does this biometric belong to the person it claims 
to belong to?  In the latter case (picking terrorists out of crowds), the 
system needs to solve a much harder problem: does this biometric belong to 
anyone in this large database of people?  The difficulty of the latter 
problem increases the complexity of the identification, and leads to 
identification failures.

Setting up the system is different for the two applications.  In the first 
case, you can unambiguously know the reference biometric belongs to the 
correct person.  In the latter case, you need to continually worry about 
the integrity of the biometric database.  What happens if someone is 
wrongfully included in the database?  What kind of right of appeal does he 
have?

Getting reference biometrics is different, too.  In the first case, you can 
initialize the system with a known, good biometric.  If the biometric is 
face recognition, you can take good pictures of new employees when they are 
hired and enter them into the system.  Terrorists are unlikely to pose for 
photo shoots.  You might have a grainy picture of a terrorist, taken five 
years ago from 1000 yards away when he had a beard.  Not nearly as useful.

But even if all these technical problems were magically solved, it's still 
very difficult to make this kind of system work.  The hardest problem is 
the false alarms.  To explain why, I'm going to have to digress into 
statistics and explain the base rate fallacy.

Suppose this magically effective face-recognition software is 99.99 percent 
accurate.  That is, if someone is a terrorist, there is a 99.99 percent 
chance that the software indicates "terrorist," and if someone is not a 
terrorist, there is a 99.99 percent chance that the software indicates 
"non-terrorist."  Assume that one in ten million flyers, on average, is a 
terrorist.  Is the software any good?

No.  The software will generate 1000 false alarms for every one real 
terrorist.  And every false alarm still means that all the security people 
go through all of their security procedures.  Because the population of 
non-terrorists is so much larger than the number of terrorists, the test is 
useless.  This result is counterintuitive and surprising, but it is 
correct.  The false alarms in this kind of system render it mostly 
useless.  It's "The Boy Who Cried Wolf" increased 1000-fold.

I say mostly useless, because it would have some positive effect.  Once in 
a while, the system would correctly finger a frequent-flyer terrorist.  But 
it's a system that has enormous costs: money to install, manpower to run, 
inconvenience to the millions of people incorrectly identified, successful 
lawsuits by some of those people, and a continued erosion of our civil 
liberties.  And all the false alarms will inevitably lead those managing 
the system to distrust its results, leading to sloppiness and potentially 
costly mistakes.  Ubiquitous harvesting of biometrics might sound like a 
good idea, but I just don't think it's worth it.

Phil Agre on face-recognition biometrics:
<http://dlis.gseis.ucla.edu/people/pagre/bar-code.html>

My original essay on biometrics:
<http://www.counterpane.com/crypto-gram-9808.html#biometrics>

Face recognition useless in airports:
<http://www.theregister.co.uk/content/4/21916.html>
According to a DARPA study, to detect 90 per cent of terrorists we'd need 
to raise an alarm for one in every three people passing through the airport.

A company that is pushing this idea:
<http://www.theregister.co.uk/content/6/21882.html>

A version of this article was published here:
<http://www.extremetech.com/article/0,3396,s%253D1024%2526a%253D15070,00.asp>


** *** ***** ******* *********** *************

        Diagnosing Intelligence Failures



It's clear that U.S. intelligence failed to provide adequate warning of the 
September 11 terrorist attacks, and that the FBI failed to prevent the 
attacks.  It's also clear that there were all sorts of indications that the 
attacks were going to happen, and that there were all sorts of things that 
we could have noticed but didn't.  Some have claimed that this was a 
massive intelligence failure, and that we should have known about and 
prevented the attacks.  I am not convinced.

There's a world of difference between intelligence data and intelligence 
information.  In what I am sure is the mother of all investigations, the 
CIA, NSA, and FBI have uncovered all sorts of data from their files, data 
that clearly indicates that an attack was being planned.  Maybe it even 
clearly indicates the nature of the attack, or the date.  I'm sure lots of 
information is there, in files, intercepts, computer memory.

Armed with the clarity of hindsight, it's easy to look at all the data and 
point to what's important and relevant.  It's even easy to take all that 
important and relevant data and turn it into information.  And it's real 
easy to take that information and construct a picture of what's going on.

It's a lot harder to do before the fact.  Most data is irrelevant, and most 
leads are false ones.  How does anyone know which is the important one, 
that effort should be spent on this specific threat and not the thousands 
of others?

So much data is collected -- the NSA sucks up an almost unimaginable 
quantity of electronic communications, the FBI gets innumerable leads and 
tips, and our allies pass all sorts of information to us -- that we can't 
possibly analyze it all.  Imagine terrorists are hiding plans for attacks 
in the text of books in a large university library; you have no idea how 
many plans there are or where they are, and the library expands faster than 
you can possibly read it.  Deciding what to look at is an impossible task, 
so a lot of good intelligence goes unlearned.

We also don't have any context to judge the intelligence effort.  How many 
terrorist attempts have been thwarted in the past year?  How many groups 
are being tracked?  If the CIA, NSA, and FBI succeed, no one ever 
knows.  It's only in failure that they get any recognition.

And it was a failure.  Over the past couple of decades, the U.S. has relied 
more and more on high-tech electronic eavesdropping (SIGINT and COMINT) and 
less and less on old fashioned human intelligence (HUMINT).  This only 
makes the analysis problem worse: too much data to look at, and not enough 
real-world context.  Look at the intelligence failures of the past few 
years: failing to predict India's nuclear test, or the attack on the USS 
Cole, or the bombing of the two American embassies in Africa; concentrating 
on Wen Ho Lee to the exclusion of the real spies, like Robert Hanssen.

But whatever the reason, we failed to prevent this terrorist attack.  In 
the post mortem, I'm sure there will be changes in the way we collect and 
(most importantly) analyze anti-terrorist data.  But calling this a massive 
intelligence failure is a disservice to those who are working to keep our 
country secure.

Intelligence failure is an overreliance on eavesdropping and not enough on 
human intelligence:
<http://www.sunspot.net/bal-te.intelligence13sep13.story>
<http://www.newscientist.com/news/news.jsp?id=ns99991297>

Another view:
<http://www.wired.com/news/politics/0,1283,46746,00.html>

Too much electronic eavesdropping only makes things harder:
<http://www.wired.com/news/business/0,1367,46817,00.html>

Israel alerted the U.S. about attacks:
<http://www.latimes.com/news/nationworld/nation/la-092001probe.story>
Mostly retracted:
<http://www.latimes.com/news/nationworld/nation/la-092101mossad.story>


** *** ***** ******* *********** *************

             Regulating Cryptography



In the wake of the devastating attacks on New York's World Trade Center and 
the Pentagon, Senator Judd Gregg and other high-ranking government 
officials quickly seized on the opportunity to resurrect limits on strong 
encryption and key escrow systems that ensure government access to 
encrypted messages.

I think this is a bad move.  It will do little to thwart terrorist 
activities, while at the same time significantly reducing the security of 
our own critical infrastructure.  We've been through these arguments 
before, but legislators seem to have short memories.  Here's why trying to 
limit cryptography is bad for Internet security.

One, you can't limit the spread of cryptography.  Cryptography is 
mathematics, and you can't ban mathematics.  All you can ban is a set of 
products that use that mathematics, but that is something quite 
different.  Years ago, during the cryptography debates, an international 
crypto survey was completed; it listed almost a thousand products with 
strong cryptography from over a hundred countries.  You might be able to 
control cryptography products in a handful of industrial countries, but 
that won't prevent criminals from importing them.  You'd have to ban them 
in every country, and even then it won't be enough.  Any terrorist 
organization with a modicum of skill can write its own cryptography 
software.  And besides, what terrorist is going to pay attention to a legal 
ban?

Two, any controls on the spread of cryptography hurt more than they 
help.  Cryptography is one of the best security tools we have to protect 
our electronic world from harm: eavesdropping, unauthorized access, 
meddling, denial of service.  Sure, by controlling the spread of 
cryptography you might be able to prevent some terrorist groups from using 
cryptography, but you'll also prevent bankers, hospitals, and air-traffic 
controllers from using it.  (And, remember, the terrorists can always get 
the stuff elsewhere: see my first point.)  We've got a lot of electronic 
infrastructure to protect, and we need all the cryptography we can get our 
hands on.  If anything, we need to make strong cryptography more prevalent 
if companies continue to put our planet's critical infrastructure online.

Three, key escrow doesn't work.  Short refresher: this is the notion that 
companies should be forced to implement back doors in crypto products such 
that law enforcement, and only law enforcement, can peek in and eavesdrop 
on encrypted messages.  Terrorists and criminals won't use it.  (Again, see 
my first point.)

Key escrow also makes it harder for the good guys to secure the important 
stuff.  All key-escrow systems require the existence of a highly sensitive 
and highly available secret key or collection of keys that must be 
maintained in a secure manner over an extended time period.  These systems 
must make decryption information quickly accessible to law enforcement 
agencies without notice to the key owners.  Does anyone really think that 
we can build this kind of system securely?  It would be a security 
engineering task of unbelievable magnitude, and I don't think we have a 
prayer of getting it right.  We can't build a secure operating system, let 
alone a secure computer and secure network.

Stockpiling keys in one place is a huge risk just waiting for attack or 
abuse.  Whose digital security do you trust absolutely and without 
question, to protect every major secret of the nation?  Which operating 
system would you use?  Which firewall?  Which applications?  As attractive 
as it may sound, building a workable key-escrow system is beyond the 
current capabilities of computer engineering.

Years ago, a group of colleagues and I wrote a paper outlining why key 
escrow is a bad idea.  The arguments in the paper still stand, and I urge 
everyone to read it.  It's not a particularly technical paper, but it lays 
out all the problems with building a secure, effective, scalable key-escrow 
infrastructure.

The events of September 11 have convinced a lot of people that we live in 
dangerous times, and that we need more security than ever before.  They're 
right; security has been dangerously lax in many areas of our society, 
including cyberspace.  As more and more of our nation's critical 
infrastructure goes digital, we need to recognize cryptography as part of 
the solution and not as part of the problem.

My old "Risks of Key Recovery" paper:
<http://www.counterpane.com/key-escrow.html>

Articles on this topic:
<http://cgi.zdnet.com/slink?140437:8469234>
<http://www.wired.com/news/politics/0,1283,46816,00.html>
<http://www.pcworld.com/news/article/0,aid,62267,00.asp>
<http://www.newscientist.com/news/news.jsp?id=ns99991309>
<http://www.zdnet.com/zdnn/stories/news/0,4586,2814833,00.html>

Al-Qaeda did not use encryption to plan these attacks:
<http://dailynews.yahoo.com/h/nm/20010918/ts/attack_investigation_dc_23.html>

Poll indicates that 72 percent of Americans believe that anti-encryption 
laws would be "somewhat" or "very" helpful in preventing a repeat of last 
week's terrorist attacks on New York's World Trade Center and the Pentagon 
in Washington, D.C.  No indication of what percentage actually understood 
the question.
<http://news.cnet.com/news/0-1005-200-7215723.html?tag=mn_hd>


** *** ***** ******* *********** *************

         Terrorists and Steganography



Guess what?  Al-Qaeda may use steganography.  According to nameless "U.S. 
officials and experts" and "U.S. and foreign officials," terrorist groups 
are "hiding maps and photographs of terrorist targets and posting 
instructions for terrorist activities on sports chat rooms, pornographic 
bulletin boards and other Web sites."

I've written about steganography in the past, and I don't want to spend 
much time retracing old ground.  Simply, steganography is the science of 
hiding messages in messages.  Typically, a message (either plaintext or, 
more cleverly, ciphertext) is encoded as tiny changes to the color of the 
pixels of a digital photograph.  Or in imperceptible noise in an audio 
file.  To the uninitiated observer, it's just a picture.  But to the sender 
and receiver, there's a message hiding in there.

It doesn't surprise me that terrorists are using this trick.  The very 
aspects of steganography that make it unsuitable for normal corporate use 
make it ideally suited for terrorist use.  Most importantly, it can be used 
in an electronic dead drop.

If you read the FBI affidavit against Robert Hanssen, you learn how Hanssen 
communicated with his Russian handlers.  They never met, but would leave 
messages, money, and documents for one another in plastic bags under a 
bridge.  Hanssen's handler would leave a signal in a public place -- a 
chalk mark on a mailbox -- to indicate a waiting package.  Hanssen would 
later collect the package.

That's a dead drop.  It has many advantages over a face-to-face 
meeting.  One, the two parties are never seen together.  Two, the two 
parties don't have to coordinate a rendezvous.  Three, and most 
importantly, one party doesn't even have to know who the other one is (a 
definite advantage if one of them is arrested).  Dead drops can be used to 
facilitate completely anonymous, asynchronous communications.

Using steganography to embed a message in a pornographic image and posting 
it to a Usenet newsgroup is the cyberspace equivalent of a dead drop.  To 
everyone else, it's just a picture.  But to the receiver, there's a message 
in there waiting to be extracted.

To make it work in practice, the terrorists would need to set up some sort 
of code.  Just as Hanssen knew to collect his package when he saw the chalk 
mark, a virtual terrorist will need to know to look for his message. (He 
can't be expected to search every picture.)  There are lots of ways to 
communicate a signal: timestamp on the message, an uncommon word in the 
subject line, etc.  Use your imagination here; the possibilities are limitless.

The effect is that the sender can transmit a message without ever 
communicating directly with the receiver.  There is no e-mail between them, 
no remote logins, no instant messages.  All that exists is a picture posted 
to a public forum, and then downloaded by anyone sufficiently enticed by 
the subject line (both third parties and the intended receiver of the 
secret message).

So, what's a counter-espionage agency to do?  There are the standard ways 
of finding steganographic messages, most of which involve looking for 
changes in traffic patterns.  If Bin Laden is using pornographic images to 
embed his secret messages, it is unlikely these pictures are being taken in 
Afghanistan.  They're probably downloaded from the Web.  If the NSA can 
keep a database of images (wouldn't that be something?), then they can find 
ones with subtle changes in the low-order bits.  If Bin Laden uses the same 
image to transmit multiple messages, the NSA could notice that.  Otherwise, 
there's probably nothing the NSA can do.  Dead drops, both real and 
virtual, can't be prevented.

Why can't businesses use this?  The primary reason is that legitimate 
businesses don't need dead drops.  I remember hearing one company talk 
about a corporation embedding a steganographic message to its salespeople 
in a photo on the corporate Web page.  Why not just send an encrypted 
e-mail?  Because someone might notice the e-mail and know that the 
salespeople all got an encrypted message.  So send a message every day: a 
real message when you need to, and a dummy message otherwise.  This is a 
traffic analysis problem, and there are other techniques to solve 
it.  Steganography just doesn't apply here.

Steganography is good way for terrorist cells to communicate, allowing 
communication without any group knowing the identity of the other.  There 
are other ways to build a dead drop in cyberspace.  A spy can sign up for a 
free, anonymous e-mail account, for example.  Bin Laden probably uses those 
too.

News articles:
<http://www.wired.com/news/print/0,1294,41658,00.html>
<http://www.usatoday.com/life/cyber/tech/2001-02-05-binladen.htm>
<http://www.sfgate.com/cgi-bin/article.cgi?file=/gate/archive/2001/09/20/sig 
intell.DTL>
<http://www.cnn.com/2001/US/09/20/inv.terrorist.search/>
<http://www.washingtonpost.com/wp-dyn/articles/A52687-2001Sep18.html>

My old essay on steganography:
<http://www.counterpane.com/crypto-gram-9810.html#steganography>

Study claims no steganography on eBay:
<http://www.theregister.co.uk/content/4/21829.html>

Detecting steganography on the Internet:
<http://www.citi.umich.edu/techreports/reports/citi-tr-01-11.pdf>

A version of this essay appeared on ZDnet:
<http://www.zdnet.com/zdnn/stories/comment/0,5859,2814256,00.html>
<http://www.msnbc.com/news/633709.asp?0dm=B12MT>


** *** ***** ******* *********** *************

                      News



I am not opposed to using force against the terrorists.  I am not opposed 
to going to war -- for retribution, deterrence, and the restoration of the 
social contract -- assuming a suitable enemy can be 
identified.  Occasionally, peace is something you have to fight for.  But I 
think the use of force is far more complicated than most people 
realize.  Our actions are important; messing this up will only make things 
worse.

Written before September 11: A former CIA operative explains why the 
terrorist Usama bin Laden has little to fear from American intelligence.
<http://www.theatlantic.com/issues/2001/07/gerecht.htm>
And a Russian soldier discusses why war in Afghanistan will be a nightmare.
<http://www.latimes.com/news/printedition/asection/la-000075191sep19.story>
A British soldier explains the same:
<http://www.sunday-times.co.uk/news/pages/sti/2001/09/23/stiusausa02023.html?>
Lessons from Britain on fighting terrorism:
<http://www.salon.com/news/feature/2001/09/19/fighting_terror/index.html>
1998 Esquire interview with Bin Ladin:
<http://www.esquire.com/features/articles/2001/010913_mfe_binladen_1.html>

Phil Agre's comments on these issues:
<http://commons.somewhere.com/rre/2001/RRE.War.in.a.World.Witho.html>
<http://commons.somewhere.com/rre/2001/RRE.Imagining.the.Next.W.html>

Why technology can't save us:
<http://www.osopinion.com/perl/story/13535.html>

Hactivism exacts revenge for terrorist attacks:
<http://news.cnet.com/news/0-1003-201-7214703-0.html?tag=owv>
FBI reminds everyone that it's illegal:
<http://www.nipc.gov/warnings/advisories/2001/01-020.htm>
<http://www.ananova.com/news/story/sm_400565.html?menu=>

Hackers face life imprisonment under anti-terrorism act:
<http://www.securityfocus.com/news/257>
Especially scary are the "advice or assistance" components.  A security 
consultant could face life imprisonment, without parole, if he discovered 
and publicized a security hole that was later exploited by someone 
else.  After all, without his "advice" about what the hole was, the 
attacker never would have accomplished his hack.

Companies fear cyberterrorism:
<http://cgi.zdnet.com/slink?140433:8469234>
<http://computerworld.com/nlt/1%2C3590%2CNAV65-663_STO63965_NLTSEC%2C00.html>
They're investing in security:
<http://www.washtech.com/news/software/12514-1.html>
<http://www.theregister.co.uk/content/55/21814.html>

Upgrading government computers to fight terrorism:
<http://www.zdnet.com/zdnn/stories/news/0,4586,5096868,00.html>

Risks of cyberterrorism attacks against our electronic infrastructure:
<http://www.businessweek.com/bwdaily/dnflash/sep2001/nf20010918_8931.htm?&_r 
ef=1732900718>
<http://cgi.zdnet.com/slink?143569:8469234>

Now the complaint is that Bin Laden is NOT using high-tech communications:
<http://www.theregister.co.uk/content/57/21790.html>

Larry Ellison is willing to give away the software to implement a national 
ID card.
<http://www.siliconvalley.com/docs/news/svfront/ellsn092301.htm>
Security problems include: inaccurate information, insiders issuing fake 
cards (this happens with state drivers' licenses), vulnerability of the 
large database, potential privacy abuses, etc.  And, of course, no 
trans-national terrorists would be listed in such a system, because they 
wouldn't be U.S. citizens.  What do you expect from a company whose origins 
are intertwined with the CIA?


** *** ***** ******* *********** *************

         Protecting Privacy and Liberty



Appalled by the recent hijackings, many Americans have declared themselves 
willing to give up civil liberties in the name of security.  They've 
declared it so loudly that this trade-off seems to be a fait 
accompli.  Article after article talks about the balance between privacy 
and security, discussing whether various increases of security are worth 
the privacy and civil-liberty losses.  Rarely do I see a discussion about 
whether this linkage is a valid one.

Security and privacy are not two sides of a teeter-totter.  This 
association is simplistic and largely fallacious.  It's easy and fast, but 
less effective, to increase security by taking away liberty.  However, the 
best ways to increase security are not at the expense of privacy and liberty.

It's easy to refute the notion that all security comes at the expense of 
liberty.  Arming pilots, reinforcing cockpit doors, and teaching flight 
attendants karate are all examples of security measures that have no effect 
on individual privacy or liberties.  So are better authentication of 
airport maintenance workers, or dead-man switches that force planes to 
automatically land at the closest airport, or armed air marshals traveling 
on flights.

Liberty-depriving security measures are most often found when system 
designers failed to take security into account from the beginning.  They're 
Band-aids, and evidence of bad security planning.  When security is 
designed into a system, it can work without forcing people to give up their 
freedoms.

Here's an example: securing a room.  Option one: convert the room into an 
impregnable vault.  Option two: put locks on the door, bars on the windows, 
and alarm everything.  Option three: don't bother securing the room; 
instead, post a guard in the room who records the ID of everyone entering 
and makes sure they should be allowed in.

Option one is the best, but is unrealistic.  Impregnable vaults just don't 
exist, getting close is prohibitively expensive, and turning a room into a 
vault greatly lessens its usefulness as a room.  Option two is the 
realistic best; combine the strengths of prevention, detection, and 
response to achieve resilient security.  Option three is the worst.  It's 
far more expensive than option two, and the most invasive and easiest to 
defeat of all three options.  It's also a sure sign of bad planning; 
designers built the room, and only then realized that they needed 
security.  Rather then spend the effort installing door locks and alarms, 
they took the easy way out and invaded people's privacy.

A more complex example is Internet security.  Preventive countermeasures 
help significantly against script kiddies, but fail against smart 
attackers.  For a couple of years I have advocated detection and response 
to provide security on the Internet.  This works; my company catches 
attackers -- both outside hackers and insiders -- all the time.  We do it 
by monitoring the audit logs of network products: firewalls, IDSs, routers, 
servers, and applications.  We don't eavesdrop on legitimate users or read 
traffic.  We don't invade privacy.  We monitor data about data, and find 
abuse that way.  No civil liberties are violated.  It's not perfect, but 
nothing is.  Still, combined with preventive security products it is more 
effective, and more cost-effective, than anything else.

The parallels between Internet security and global security are 
strong.  All criminal investigation looks at surveillance records.  The 
lowest-tech version of this is questioning witnesses.  In this current 
investigation, the FBI is looking at airport videotapes, airline passenger 
records, flight school class records, financial records, etc.  And the 
better job they can do examining these records, the more effective their 
investigation will be.

There are copycat criminals and terrorists, who do what they've seen done 
before.  To a large extent, this is what the hastily implemented security 
measures have tried to prevent.  And there are the clever attackers, who 
invent new ways to attack people.  This is what we saw on September 
11.  It's expensive, but we can build security to protect against 
yesterday's attacks.  But we can't guarantee protection against tomorrow's 
attacks: the hacker attack that hasn't been invented, or the terrorist 
attack yet to be conceived.

Demands for even more surveillance miss the point.  The problem is not 
obtaining data, it's deciding which data is worth analyzing and then 
interpreting it.  Everyone already leaves a wide audit trail as we go 
through life, and law enforcement can already access those records with 
search warrants.  The FBI quickly pieced together the terrorists' 
identities and the last few months of their lives, once they knew where to 
look.  If they had thrown up their hands and said that they couldn't figure 
out who did it or how, they might have a case for needing more surveillance 
data.  But they didn't, and they don't.

More data can even be counterproductive.  The NSA and the CIA have been 
criticized for relying too much on signals intelligence, and not enough on 
human intelligence.  The East German police collected data on four million 
East Germans, roughly a quarter of their population.  Yet they did not 
foresee the peaceful overthrow of the Communist government because they 
invested heavily in data collection instead of data interpretation.  We 
need more intelligence agents squatting on the ground in the Middle East 
arguing the Koran, not sitting in Washington arguing about wiretapping laws.

People are willing to give up liberties for vague promises of security 
because they think they have no choice.  What they're not being told is 
that they can have both.  It would require people to say no to the FBI's 
power grab.  It would require us to discard the easy answers in favor of 
thoughtful answers.  It would require structuring incentives to improve 
overall security rather than simply decreasing its costs.  Designing 
security into systems from the beginning, instead of tacking it on at the 
end, would give us the security we need, while preserving the civil 
liberties we hold dear.

Some broad surveillance, in limited circumstances, might be warranted as a 
temporary measure.  But we need to be careful that it remain temporary, and 
that we do not design surveillance into our electronic 
infrastructure.  Thomas Jefferson once said:  "Eternal vigilance is the 
price of liberty."  Historically, liberties have always been a casualty of 
war, but a temporary casualty.  This war -- a war without a clear enemy or 
end condition -- has the potential to turn into a permanent state of 
society.  We need to design our security accordingly.

The events of September 11th demonstrated the need for America to redesign 
our public infrastructures for security.  Ignoring this need would be an 
additional tragedy.

Quotes from U.S. government officials on the need to preserve liberty 
during this crisis:
<http://www.epic.org/alert/EPIC_Alert_8.17.html>

Quotes from editorial pages on the same need:
<http://www.epic.org/alert/EPIC_Alert_8.18.html>

Selected editorials:
<http://www.nytimes.com/2001/09/16/weekinreview/16GREE.html>
<http://www.nytimes.com/2001/09/23/opinion/23SUN1.html>
<http://www.freedomforum.org/templates/document.asp?documentID=14924>

Schneier's comments in the UK:
<http://www.theregister.co.uk/content/55/21892.html>

War and liberties:
<http://www.salon.com/tech/feature/2001/09/22/end_of_liberty/index.html>
<http://www.washingtonpost.com/wp-dyn/articles/A21207-2001Sep12.html>
<http://www.wired.com/news/politics/0,1283,47051,00.html>

More on Ashcroft's anti-privacy initiatives:
<http://www.theregister.co.uk/content/6/21854.html>

Editorial cartoon:
<http://www.claybennett.com/pages/latest_08.html>

Terrorists leave a broad electronic trail:
<http://www.wired.com/news/politics/0,1283,46991,00.html>

National Review article from 1998: "Know nothings: U.S. intelligence 
failures stem from too much information, not enough understanding"
<http://www.findarticles.com/m1282/n14_v50/21102283/p1/article.jhtml>

A previous version of this essay appeared in the San Jose Mercury News:
<http://www0.mercurycenter.com/premium/opinion/columns/security27.htm>


** *** ***** ******* *********** *************

                     How to Help



How can you help?  Speak about the issues.  Write to your elected 
officials.  Contribute to organizations working on these issues.

This week the United States Congress will act on the most sweeping proposal 
to extend the surveillance authority of the government since the end of the 
Cold War. If you value privacy, there are three steps you should take 
before you open your next email message:

1. Urge your representatives in Congress to protect privacy.
- Call the White House switchboard at 202-224-3121.
- Ask to be connected to the office of your Congressional representative.
- When you are put through, say "May I please speak to the staff member who 
is working on the anti-terrorism legislation?" If that person is not 
available to speak with you, say  "May I please leave a message?"
- Briefly explain that you appreciate the efforts of your representative to 
address the challenges brought about by the September 11th tragedy, but it 
is your view that it would be a mistake to make any changes in the federal 
wiretap statute that do not respond to "the immediate threat of 
investigating or preventing terrorist acts."

2. Go to the In Defense of Freedom web site and endorse the 
statement:  <http://www.indefenseoffreedom.org>

3. Forward this message to at least five other people.

We have less than 100 hours before Congress acts on legislation that will 
(a) significantly expand the use of Carnivore, (b) make computer hacking a 
form of terrorism, (c) expand electronic surveillance in routine criminal 
investigations, and (d) reduce government accountability.

Please act now.

More generally, I expect to see many pieces of legislation that will 
address these matters.  Visit the following Web sites for up-to-date 
information on what is happening and what you can do to help.

The Electronic Privacy Information Center:
<http://www.epic.org>

The Center for Democracy and Technology:
<http://www.cdt.org>

The American Civil Liberties Union:
<http://www.aclu.org>


** *** ***** ******* *********** *************

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CRYPTO-GRAM is written by Bruce Schneier.  Schneier is founder and CTO of 
Counterpane Internet Security Inc., the author of "Secrets and Lies" and 
"Applied Cryptography," and an inventor of the Blowfish, Twofish, and 
Yarrow algorithms.  He is a member of the Advisory Board of the Electronic 
Privacy Information Center (EPIC).  He is a frequent writer and lecturer on 
computer security and cryptography.

Counterpane Internet Security, Inc. is the world leader in Managed Security 
Monitoring.  Counterpane's expert security analysts protect networks for 
Fortune 1000 companies world-wide.

<http://www.counterpane.com/>

Copyright (c) 2001 by Counterpane Internet Security, Inc.