Crypto-Gram Newsletter

December 15, 2007

by Bruce Schneier
Founder and CTO
BT Counterpane

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

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You can read this issue on the web at <>. These same essays appear in the "Schneier on Security" blog: <>. An RSS feed is available.

In this issue:

How to Secure Your Computer, Disks, and Portable Drives

Computer security is hard. Software, computer and network security are all ongoing battles between attacker and defender. And in many cases the attacker has an inherent advantage: He only has to find one network flaw, while the defender has to find and fix every flaw.

Cryptography is an exception. As long as you don't write your own algorithm, secure encryption is easy. And the defender has an inherent mathematical advantage: Longer keys increase the amount of work the defender has to do linearly, while geometrically increasing the amount of work the attacker has to do.

Unfortunately, cryptography can't solve most computer-security problems. The one problem cryptography *can* solve is the security of data when it's not in use. Encrypting files, archives -- even entire disks -- is easy.

All of this makes it even more amazing that Her Majesty's Revenue & Customs in the United Kingdom lost two disks with personal data on 25 million British citizens, including dates of birth, addresses, bank-account information and national insurance numbers. On the one hand, this is no bigger a deal than any of the thousands of other exposures of personal data we've read about in recent years -- the U.S. Veteran's Administration loss of personal data of 26 million American veterans is an obvious similar event. But this has turned into Britain's privacy Chernobyl.

Perhaps encryption isn't so easy after all, and some people could use a little primer. This is how I protect my laptop.

There are several whole-disk encryption products on the market. I use PGP Disk's Whole Disk Encryption tool for two reasons. It's easy, and I trust both the company and the developers to write it securely. (Disclosure: I'm also on PGP Corp.'s Technical Advisory Board.)

Setup only takes a few minutes. After that, the program runs in the background. Everything works like before, and the performance degradation is negligible. Just make sure you choose a secure password -- PGP's encouragement of passphrases makes this much easier -- and you're secure against leaving your laptop in the airport or having it stolen out of your hotel room.

The reason you encrypt your entire disk, and not just key files, is so you don't have to worry about swap files, temp files, hibernation files, erased files, browser cookies or whatever. You don't need to enforce a complex policy about which files are important enough to be encrypted. And you have an easy answer to your boss or to the press if the computer is stolen: no problem; the laptop is encrypted.

PGP Disk can also encrypt external disks, which means you can also secure that USB memory device you've been using to transfer data from computer to computer. When I travel, I use a portable USB drive for backup. Those devices are getting physically smaller -- but larger in capacity -- every year, and by encrypting I don't have to worry about losing them.

I recommend one more complication. Whole-disk encryption means that anyone at your computer has access to everything: someone at your unattended computer, a Trojan that infected your computer and so on. To deal with these and similar threats I recommend a two-tier encryption strategy. Encrypt anything you don't need access to regularly -- archived documents, old e-mail, whatever -- separately, with a different password. I like to use PGP Disk's encrypted zip files, because it also makes secure backup easier (and lets you secure those files before you burn them on a DVD and mail them across the country), but you can also use the program's virtual-encrypted-disk feature to create a separately encrypted volume. Both options are easy to set up and use.

There are still two scenarios you aren't secure against, though. You're not secure against someone snatching your laptop out of your hands as you're typing away at the local coffee shop. And you're not secure against the authorities telling you to decrypt your data for them.

The latter threat is becoming more real. I have long been worried that someday, at a border crossing, a customs official will open my laptop and ask me to type in my password. Of course I could refuse, but the consequences might be severe -- and permanent. And some countries -- the United Kingdom, Singapore, Malaysia -- have passed laws giving police the authority to demand that you divulge your passwords and encryption keys.

To defend against both of these threats, minimize the amount of data on your laptop. Do you really need 10 years of old e-mails? Does everyone in the company really need to carry around the entire customer database? One of the most incredible things about the Revenue & Customs story is that a low-level government employee mailed a copy of the entire national child database to the National Audit Office in London. Did he have to? Doubtful. The best defense against data loss is to not have the data in the first place.

Failing that, you can try to convince the authorities that you don't have the encryption key. This works better if it's a zipped archive than the whole disk. You can argue that you're transporting the files for your boss, or that you forgot the key long ago. Make sure the time stamp on the files matches your claim, though.

There are other encryption programs out there. If you're a Windows Vista user, you might consider BitLocker. This program, embedded in the operating system, also encrypts the computer's entire drive. But it only works on the C: drive, so it won't help with external disks or USB tokens. And it can't be used to make encrypted zip files. But it's easy to use, and it's free. And many people like the open-source and free program, TrueCrypt. I know nothing about it.

This essay previously appeared on

Why was the UK event such a big deal? Certainly the scope: 40% of the British population. Also the data: bank account details; plus information about children. There's already a larger debate on the issue of a database on kids that this feeds into. And it's a demonstration of government incompetence (think Hurricane Katrina). In any case, this issue isn't going away anytime soon. Prime Minister Gordon Brown has apologized. The head of the Revenue and Customs office has resigned. More fallout is probably coming.

UK's privacy Chernobyl:

U.S. VA privacy breach:

PGP Disk:

Choosing a secure password:

Risks of losing small memory devices:

Laptop snatching:
Microsoft BitLocker:


Defeating the Shoe Scanning Machine at Heathrow Airport

For a while now, Terminal 3 at Heathrow Airport has had a unique setup for scanning shoes. Instead of taking your shoes off during the normal screening process, as you do in U.S. airports, you go through the metal detector with your shoes on. Then, later, there is a special shoe scanning X-ray machine. You take your shoes off, send them through the machine, and put them on at the other end.

It's definitely faster, but it's an easy system to defeat. The vulnerability is that no one verifies that the shoes you walked through the metal detector with are the same shoes you put on the scanning machine.

Here's how the attack works. Assume that you have two pairs of shoes: a clean pair that passes all levels of screening, and a dangerous pair that doesn't. (Ignore for a moment the ridiculousness of screening shoes in the first place, and assume that an X-ray machine can detect the dangerous pair.) Put the dangerous shoes on your feet and the clean shoes in your carry-on bag. Walk through the metal detector. Then, at the shoe X-ray machine, take the dangerous shoes off and put them in your bag, and take the clean shoes out of your bag and place them on the X-ray machine. You've now managed to get through security without having your shoes screened.

This works because the two security systems are decoupled. And the shoe screening machine is so crowded and chaotic, and so poorly manned, that no one notices the switch.

U.S. airports force people to put their shoes through the X-ray machine and walk through the metal detector shoeless, ensuring that all shoes get screened. That might be slower, but it works.


Dan Bernstein wrote an interesting paper on the security lessons he's learned from qmail.

Possible Hizbullah mole inside the FBI and CIA

I previously wrote about Dan Egerstad, a security researcher who ran a Tor anonymity network and was able to sniff some pretty impressive usernames and passwords. Swedish police arrested him last month.
My previous essay:
Here's a good article on what he did; it was published just before the arrest.
The World War II factoring machine, Colossus, is back online.
Not surprisingly, a modern PC is faster.

Hacking a soda machine: an instructional video. The idea is simple: prevent the machine from completing an action and place it in an error state, and then exploit that state. In this instance, the hacker prevents the machine from dispensing the drink bottle. The machine refunds the money, but the bottle stays on the conveyor belt. Then the hacker purchases a second bottle, and receives them both.

This is a story of hard drives sold with pre-installed Trojans. I don't know if it's true, but it's certainly possible:

More "War on the Unexpected."
In Australia, a man was kicked out of a pub for reading a book called "The Unknown Terrorist."
At the US/Canadian border, a fire truck responding to a fire -- with lights and sirens -- was stopped for about eight minutes.
Police tasered a man on a Leeds bus when he went into a diabetic coma.
A mixture of flour and sugar closed down a Maine airport:
A blind calypso musician and his band removed from an airplane:
A Jewish man removed from a train for praying:
A bomb squad in Sarasota, Florida, is called in to detonate a typewriter:
Fear is winning. Refuse to be terrorized, people.

At first, I discounted this story of fake dynamite prompting an evacuation as another example of knee-jerk overreaction to a nonexistent threat. Evacuating everyone within a mile radius seemed excessive, even for real dynamite.
But assuming that the information in this article is correct, it might not have been that big an overreaction. It was an intentional bomb threat hoax.

No two-person control or complicated safety features: until 1998, you could arm British nukes with a bicycle lock key. Certainly most of the security was procedural. But still....

"Passengers at Liverpool's Lime Street station face airport-style searches and bag-screening, under swingeing new anti-terror measures unveiled yesterday. And security barriers, vehicle exclusion zones and blast-resistant buildings will be introduced at airports, ports and up to 250 of the busiest train stations, Gordon Brown announced." What the headline should have read: "UK Spends Billions to Force Rail Terrorists to Drive a Little Further." Less busy stations are only a few minutes away by car.
Clever way of using Google to crack hashed passwords:
Excellent article on the problem with copyright law by John Tehranian: "Infringement Nation: Copyright Reform and the Law/Norm Gap." The point of the article is how, simply by acting normally, all of us are technically lawbreakers many times over every day. When laws are this far outside the social norms, it's time to change them.
In yet another front on the war on the unexpected, firefighters are being asked to look out for terrorism while doing their normal jobs. "Unlike police, firefighters and emergency medical personnel don't need warrants to access hundreds of thousands of homes and buildings each year, putting them in a position to spot behavior that could indicate terrorist activity or planning." Because it's such a good idea for people to start fearing firefighters....
Good article on cybercrime vs. cyberterrorism, and stuff I've been saying for a while now.

Animal rights activists are being forced to hand over encryption keys, based on a new UK law.
More about the new law here. If you remember, this was sold to the public as essential for fighting terrorism. It's already being misused.

How to harvest passwords: Just put up a password strength meter and encourage people to submit their passwords for testing. You might want to collect names and e-mail addresses, too.
Note that I am not accusing Codeassembly of harvesting passwords, only pointing out that you could harvest passwords that way. For the record, here's how to choose a secure password:

Movie-plot threat described in the press as a movie-plot threat.
In the end, it was nothing more than fiction (of course).

Trucker drives through the front gate of the Guinness brewery in Dublin and steals 450 kegs of beer. Moral, look like you belong.
It seems they were caught before they drank it all.

Every year SANS publishes a list of the 20 most important vulnerabilities. It's always a great list, and this year is no different.

MI5 sounds alarm on internet spying from China. This has been going on for years, so why did MI5 go public -- or, at least, send out a private document that was sure to be leaked? At first, I thought that someone in MI5 was pissed off at China. But now I think that someone in MI5 was pissed that he wasn't getting any budget.
Microsoft's wireless keyboard encryption cracked:
California's Secretary of State doubts that electronic voting machines will ever be good enough to use in her state's elections:
Ed Felten comments:
I've written a lot on this issue:

Man-in-the-middle attack by Tor exit node. So often man-in-the-middle attacks are theoretical; it's fascinating to see one in the wild.
The guy claims that he just misconfigured his Tor node. I don't know enough about Tor to have any comment about this.
I've written about anonymity and the Tor network before.

Fascinating article on how an overdependence on technology hurt us in Iraq.
Bizarre new security risk: blankets.

Monopoly sets with real money for World War II POWs:

Interesting blog post on defeating CAPTCHAs:
This group is the best out there at defeating CAPTCHAs:

The "Handbook of Applied Cryptography" is available online -- legitimately. This is a good book, and well worth downloading.

Teen secretly records his police interrogation session, resulting in a perjury case against a detective. My guess is that this sort of perjury occurs more than we realize. If there's one place I think cameras should be rolling at all times, it's in police station interrogation rooms.

Local police are putting yellow stickers on cars with visible packages, making it easier for thieves to identify which cars are worth breaking into.
Interesting study on the effects of security-breach notification laws in the U.S.

Secret bank vault plans found in German trash:
"Time Magazine" article on Chinese hackers.

"Security Question," short fiction by Ramon Rozas III.

Gitmo Manual Leaked

A 2003 "Camp Delta Standard Operating Procedures" manual has been leaked to the Internet. This is the same manual that the ACLU has unsuccessfully sued the government to get a copy of. Others can debate the legality of some of the procedures; on my blog I was interested in comments about the security.

See, for example, this quote on page 27.3:

"b) Upon arrival will enter the gate by entering the number (1998) in the combination lock

"(c) Proceed to the junction box with the number (7012-83) Breaker Box and open the box. The number for the lock on the breaker box is (224)."

Many more comments from readers online.


Other articles:

Blog entry:

Schneier/BT Counterpane News

I did a Q&A on the Freakonomics blog. Nothing regular readers of this blog haven't heard before, but it was fun all the same.
There's also a Slashdot thread on the Q&A.

Security in Ten Years

This is a conversation between myself and Marcus Ranum. Usually, I only reprint my half of these exchanges. But since this one has multiple back and forths, it only really makes sense to include the whole thing.

Bruce Schneier: Predictions are easy and difficult. Roy Amara of the Institute for the Future once said: "We tend to overestimate the effect of a technology in the short run and underestimate the effect in the long run."

Moore's Law is easy: In 10 years, computers will be 100 times more powerful. My desktop will fit into my cell phone, we'll have gigabit wireless connectivity everywhere, and personal networks will connect our computing devices and the remote services we subscribe to. Other aspects of the future are much more difficult to predict. I don't think anyone can predict what the emergent properties of 100x computing power will bring: new uses for computing, new paradigms of communication. A 100x world will be different, in ways that will be surprising.

But throughout history and into the future, the one constant is human nature. There hasn't been a new crime invented in millennia. Fraud, theft, impersonation and counterfeiting are perennial problems that have been around since the beginning of society. During the last 10 years, these crimes have migrated into cyberspace, and over the next 10, they will migrate into whatever computing, communications and commerce platforms we're using.

The nature of the attacks will be different: the targets, tactics and results. Security is both a trade-off and an arms race, a balance between attacker and defender, and changes in technology upset that balance. Technology might make one particular tactic more effective, or one particular security technology cheaper and more ubiquitous. Or a new emergent application might become a favored target.

I don't see anything by 2017 that will fundamentally alter this. Do you?

Marcus Ranum: I think you're right; at a meta-level, the problems are going to stay the same. What's shocking and disappointing to me is that our responses to those problems also remain the same, in spite of the obvious fact that they aren't effective. It's 2007 and we haven't seemed to accept that:

* You can't turn shovelware into reliable software by patching it a whole lot.

*You shouldn't mix production systems with non-production systems.

* You actually have to know what's going on in your networks.

* If you run your computers with an open execution runtime model you'll always get viruses, spyware and Trojan horses.

* You can pass laws about locking barn doors after horses have left, but it won't put the horses back in the barn.

* Security has to be designed in, as part of a system plan for reliability, rather than bolted on afterward.

The list could go on for several pages, but it would be too depressing. It would be "Marcus' list of obvious stuff that everybody knows but nobody accepts."

You missed one important aspect of the problem: By 2017, computers will be even more important to our lives, economies and infrastructure.

If you're right that crime remains a constant, and I'm right that our responses to computer security remain ineffective, 2017 is going to be a lot less fun than 2007 was.

I've been pretty dismissive of the concepts of cyberwar and cyberterror. That dismissal was mostly motivated by my observation that the patchworked and kludgy nature of most computer systems acts as a form of defense in its own right, and that real-world attacks remain more cost-effective and practical for terror purposes.

I'd like to officially modify my position somewhat: I believe it's increasingly likely that we'll suffer catastrophic failures in critical infrastructure systems by 2017. It probably won't be terrorists that do it, though. More likely, we'll suffer some kind of horrible outage because a critical system was connected to a non-critical system that was connected to the Internet so someone could get to MySpace -- and that ancillary system gets a piece of malware. Or it'll be some incomprehensibly complex software, layered with Band-Aids and patches, that topples over when some "merely curious" hacker pushes the wrong e-button. We've got some bad-looking trend lines; all the indicators point toward a system that is more complex, less well-understood and more interdependent. With infrastructure like that, who needs enemies?

You're worried criminals will continue to penetrate into cyberspace, and I'm worried complexity, poor design and mismanagement will be there to meet them.

Bruce Schneier: I think we've already suffered that kind of critical systems failure. The August 2003 blackout that covered much of northeastern United States and Canada -- 50 million people -- was caused by a software bug.

I don't disagree that things will continue to get worse. Complexity is the worst enemy of security, and the Internet -- and the computers and processes connected to it -- is getting more complex all the time. So things are getting worse, even though security technology is improving. One could say those critical insecurities are another emergent property of the 100x world of 2017.

Yes, IT systems will continue to become more critical to our infrastructure -- banking, communications, utilities, defense, everything.

By 2017, the interconnections will be so critical that it will probably be cost-effective -- and low-risk -- for a terrorist organization to attack over the Internet. I also deride talk of cyberterror today, but I don't think I will in another 10 years.

While the trends of increased complexity and poor management don't look good, there is another trend that points to more security -- but neither you nor I is going to like it. That trend is IT as a service.

By 2017, people and organizations won't be buying computers and connectivity the way they are today. The world will be dominated by telcos, large ISPs and systems integration companies, and computing will look a lot like a utility. Companies will be selling services, not products: email services, application services, entertainment services. We're starting to see this trend today, and it's going to take off in the next 10 years. Where this affects security is that by 2017, people and organizations won't have a lot of control over their security. Everything will be handled at the ISPs and in the backbone. The free-wheeling days of general-use PCs will be largely over. Think of the iPhone model: You get what Apple decides to give you, and if you try to hack your phone, they can disable it remotely. We techie geeks won't like it, but it's the future. The Internet is all about commerce, and commerce won't survive any other way.

Marcus Ranum: You're right about the shift toward services -- it's the ultimate way to lock in customers.

If you can make it difficult for the customer to get his data back after you've held it for a while, you can effectively prevent the customer from ever leaving. And of course, customers will be told "trust us, your data is secure," and they'll take that for an answer. The back-end systems that will power the future of utility computing are going to be just as full of flaws as our current systems. Utility computing will also completely fail to address the problem of transitive trust unless people start shifting to a more reliable endpoint computing platform.

That's the problem with where we're heading: the endpoints are not going to get any better. People are attracted to appliances because they get around the headache of system administration (which, in today's security environment, equates to "endless patching hell"), but underneath the slick surface of the appliance we'll have the same insecure nonsense we've got with general-purpose desktops. In fact, the development of appliances running general-purpose operating systems really does raise the possibility of a software monoculture. By 2017, do you think system engineering will progress to the point where we won't see a vendor release a new product and instantly create an installed base of 1 million-plus users with root privileges? I don't, and that scares me.

So if you're saying the trend is to continue putting all our eggs in one basket and blithely trusting that basket, I agree.

Another trend I see getting worse is government IT know-how. At the rate outsourcing has been brain-draining the federal workforce, by 2017 there won't be a single government employee who knows how to do anything with a computer except run PowerPoint and Web surf. Joking aside, the result is that the government's critical infrastructure will be almost entirely managed from the outside. The strategic implications of such a shift have scared me for a long time; it amounts to a loss of control over data, resources and communications.

Bruce Schneier: You're right about the endpoints not getting any better. I've written again and again how measures like two-factor authentication aren't going to make electronic banking any more secure. The problem is if someone has stuck a Trojan on your computer, it doesn't matter how many ways you authenticate to the banking server; the Trojan is going to perform illicit transactions after you authenticate.

It's the same with a lot of our secure protocols. SSL, SSH, PGP and so on all assume the endpoints are secure, and the threat is in the communications system. But we know the real risks are the endpoints.

And a misguided attempt to solve this is going to dominate computing by 2017. I mentioned software-as-a-service, which you point out is really a trick that allows businesses to lock up their customers for the long haul. I pointed to the iPhone, whose draconian rules about who can write software for that platform accomplishes much the same thing. We could also point to Microsoft's Trusted Computing, which is being sold as a security measure but is really another lock-in mechanism designed to keep users from switching to "unauthorized" software or OSes.

I'm reminded of the post-9/11 anti-terrorist hysteria -- we've confused security with control, and instead of building systems for real security, we're building systems of control. Think of ID checks everywhere, the no-fly list, warrantless eavesdropping, broad surveillance, data mining, and all the systems to check up on scuba divers, private pilots, peace activists and other groups of people. These give us negligible security, but put a whole lot of control in the government's hands.

Computing is heading in the same direction, although this time it is industry that wants control over its users. They're going to sell it to us as a security system -- they may even have convinced themselves it will improve security -- but it's fundamentally a control system. And in the long run, it's going to hurt security.

Imagine we're living in a world of Trustworthy Computing, where no software can run on your Windows box unless Microsoft approves it. That brain drain you talk about won't be a problem, because security won't be in the hands of the user. Microsoft will tout this as the end of malware, until some hacker figures out how to get his software approved. That's the problem with any system that relies on control: Once you figure out how to hack the control system, you're pretty much golden. So instead of a zillion pesky worms, by 2017 we're going to see fewer but worse super worms that sail past our defenses.

By then, though, we'll be ready to start building real security. As you pointed out, networks will be so embedded into our critical infrastructure -- and there'll probably have been at least one real disaster by then -- that we'll have no choice. The question is how much we'll have to dismantle and build over to get it right.

Marcus Ranum: I agree regarding your gloomy view of the future. It's ironic the counterculture "hackers" have enabled (by providing an excuse) today's run-patch-run-patch-reboot software environment and tomorrow's software Stalinism.

I don't think we're going to start building real security. Because real security is not something you build -- it's something you get when you leave out all the other garbage as part of your design process. Purpose-designed and purpose-built software is more expensive to build, but cheaper to maintain. The prevailing wisdom about software return on investment doesn't factor in patching and patch-related downtime, because if it did, the numbers would stink. Meanwhile, I've seen purpose-built Internet systems run for years without patching because they didn't rely on bloated components. I doubt industry will catch on.

The future will be captive data running on purpose-built back-end systems -- and it won't be a secure future, because turning your data over always decreases your security. Few possess the understanding of complexity and good design principles necessary to build reliable or secure systems. So, effectively, outsourcing -- or other forms of making security someone else's problem -- will continue to seem attractive.
That doesn't look like a very rosy future to me. It's a shame, too, because getting this stuff correct is important. You're right that there are going to be disasters in our future.

I think they're more likely to be accidents where the system crumbles under the weight of its own complexity, rather than hostile action. Will we even be able to figure out what happened, when it happens?

Folks, the captains have illuminated the "Fasten your seat belts" sign. We predict bumpy conditions ahead.

This essay originally appeared in "Information Security Magazine."

Commentary on the point/counterpoint.

Slashdot thread:

Comments from Readers

There are hundreds of comments -- many of them interesting -- on these topics on my blog. Search for the story you want to comment on, and join in.

CRYPTO-GRAM is a free monthly newsletter providing summaries, analyses, insights, and commentaries on security: computer and otherwise. You can subscribe, unsubscribe, or change your address on the Web at <>. Back issues are also available at that URL.

Please feel free to forward CRYPTO-GRAM, in whole or in part, to colleagues and friends who will find it valuable. Permission is also granted to reprint CRYPTO-GRAM, as long as it is reprinted in its entirety.

CRYPTO-GRAM is written by Bruce Schneier. Schneier is the author of the best sellers "Beyond Fear," "Secrets and Lies," and "Applied Cryptography," and an inventor of the Blowfish and Twofish algorithms. He is founder and CTO of BT Counterpane, and is a member of the Board of Directors of the Electronic Privacy Information Center (EPIC). He is a frequent writer and lecturer on security topics. See <>.

BT Counterpane is the world's leading protector of networked information - the inventor of outsourced security monitoring and the foremost authority on effective mitigation of emerging IT threats. BT Counterpane protects networks for Fortune 1000 companies and governments world-wide. See <>.

Crypto-Gram is a personal newsletter. Opinions expressed are not necessarily those of BT or BT Counterpane.

Copyright (c) 2007 by Bruce Schneier.

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