May 15, 2000
by Bruce Schneier
Founder and CTO
Counterpane Internet Security, Inc.
A free monthly newsletter providing summaries, analyses, insights, and commentaries on computer security and cryptography.
Back issues are available at http://www.schneier.com. To subscribe or unsubscribe, see below.
Copyright (c) 2000 by Counterpane Internet Security, Inc.
In this issue:
- Computer Security: Will We Ever Learn?
- Counterpane Internet Security News
- The Doghouse: Cybercrime Treaty
- More on Microsoft Kerberos
- Trusted Client Software
- ILOVEYOU Virus
- Comments from Readers
If we've learned anything from the past couple of years, it's that computer security flaws are inevitable. Systems break, vulnerabilities are reported in the press, and still many people put their faith in the next product, or the next upgrade, or the next patch. "This time it's secure," they say. So far, it hasn't been.
Security is a process, not a product. Products provide some protection, but the only way to effectively do business in an insecure world is to put processes in place that recognize the inherent insecurity in the products. The trick is to reduce your risk of exposure regardless of the products or patches.
Consider denial-of-service attacks. DoS attacks are some of the oldest and easiest attacks in the book. Even so, in February 2000, coordinated, distributed DoS attacks easily brought down several high-traffic Web sites, including Yahoo, eBay, Amazon.com and CNN.
Consider buffer overflow attacks. They were first talked about as early as the 1960s -- time-sharing systems suffered from the problem -- and were known by the security literati even earlier than that. In the 1970s, they were often used as a point of attack against early networked computers. In 1988, the Morris Worm exploited a buffer overflow in the Unix fingerd daemon: a very public use of this type of attack.
Today, over a decade after Morris and about 35 years after these attacks were first discovered, you'd think the security community would have solved the problem of security vulnerabilities based on buffer overflows. Think again. Over two-thirds of all CERT advisories in 1998 were for vulnerabilities caused by buffer overflows. During an average week in 1999, buffer overflow vulnerabilities were found in the RSAREF cryptographic toolkit (oops), HP's operating system, the Solaris operating system, Microsoft IIS 4.0 and Site Server 3.0, Windows NT, and Internet Explorer. A recent study named buffer overflows as the most common security problem.
Consider encryption algorithms. Proprietary secret algorithms are regularly published and broken. Again and again, the marketplace learns that proprietary secret algorithms are a bad idea. But companies and industries -- like Microsoft, the DVD consortium, cellular phone providers, and so on -- continue to choose proprietary algorithms over public, free alternatives.
Is Anyone Paying Attention?
Sadly, the answer to this question is: not really. Or at least, there are far fewer people paying attention than should be. And the enormous need for digital security products necessitates people to design, develop and implement them. The resultant dearth of experts means that the percentage of people paying attention will get even smaller.
Most products that use security are not designed by anyone with security expertise. Even security products are generally designed and implemented by people who have only limited security expertise. Security cannot be functionality tested -- no amount of beta testing will uncover security flaws -- so the flaws end up in fielded products.
I'm constantly amazed by the kinds of things that break security products. I've seen a file encryption product with a user interface that accidentally saves the key in the clear. I've seen VPNs where the telephone configuration file accidentally allows a random person to authenticate himself to the server, or that allows one remote client to view the files of another remote client. There are a zillion ways to make a product insecure, and manufacturers manage to stumble on a lot of those ways again and again.
No one is paying attention because no one has to.
Computer security products, like software in general, have a very odd product quality model. It's unlike an automobile, a skyscraper, or a box of fried chicken. If you buy a product, and get harmed because of a manufacturer's defect, you can sue...and you'll win. Car-makers can't get away with building cars that explode on impact; chicken shops can't get away with selling buckets of fried chicken with the odd rat mixed in. It just wouldn't do for building contractors to say thing like, "Whoops. There goes another one. Sorry. But just wait for Skyscraper 1.1; it'll be 100% collapse-free!"
Software is different. It is sold without any claims whatsoever. Your accounts receivable database can crash, taking your company down with it, and you have no claim against the software company. Your word processor can accidentally corrupt your files and you have no recourse. Your firewall can turn out to be completely ineffectual -- hardly better than having nothing at all -- and yet it's your fault. Microsoft fielded Hotmail with a bug that allowed anyone to read the accounts of 40 or so million subscribers, password or no password, and never bothered to apologize.
Software manufacturers don't have to produce a quality product because there is no liability if they don't. And the effect of this for security products is that manufacturers don't have to produce products that are actually secure, because no one can sue them if they make a bunch of false claims of security.
The upshot of this is that the marketplace does not reward real security. Real security is harder, slower, and more expensive, both to design and to implement. Since the buying public has no way to differentiate real security from bad security, the way to win in this marketplace is to design software that is as insecure as you can possibly get away with.
Microsoft knows that reliable software is not cost effective. According to studies, 90% to 95% of all bugs are harmless. They're never discovered by users, and they don't affect performance. It's much cheaper to release buggy software and fix the 5% to 10% of bugs people find and complain about.
Microsoft also knows that real security is not cost-effective. They get whacked with a new security vulnerability several times a week. They fix the ones they can, write misleading press releases about the ones they can't, and wait for the press fervor to die down (which it always does). And six months later they issue the next software version with new features and all sorts of new insecurities, because users prefer cool features to security.
The only solution is to look for security processes.
There's no such thing as perfect security. Interestingly enough, that's not necessarily a problem. In the U.S. alone, the credit card industry loses $10 billion to fraud per year; neither Visa nor MasterCard is showing any sign of going out of business. Shoplifting estimates in the U.S. are currently between $9.5 billion and $11 billion per year, but you never see "shrinkage" (as it is called) cited as the cause when a store goes out of business. Recently, I needed to notarize a document. That is about the stupidest security protocol I've ever seen. Still, it works fine for what it is.
Security does not have to be perfect, but the risks have to be manageable. The credit card industry understands this. They know how to estimate the losses due to fraud. Their problem is that losses from phone credit card transactions are about five times the losses from face-to-face transactions (when the card is present). Losses from Internet transactions are many times those of phone transactions, and are the driving force behind SET.
My primary fear about cyberspace is that people don't understand the risks, and they are putting too much faith in technology's ability to obviate them. Products alone cannot solve security problems.
The digital security industry is in desperate need of a perceptual shift. Countermeasures are sold as ways to counter threats. Good encryption is sold as a way to prevent eavesdropping. A good firewall is a way to prevent network attacks. PKI is sold as trust management, so you can avoid mistakenly trusting people you really don't. And so on.
This type of thinking is completely backward. Security is old, older than computers. And the old-guard security industry thinks of countermeasures not as ways to counter threats, but as ways to avoid risk. This distinction is enormous. Avoiding threats is black and white: either you avoid the threat, or you don't. Avoiding risk is continuous: there is some amount of risk you can accept, and some amount you can't.
Security processes are how you avoid risk. Just as businesses use the processes of double-entry bookkeeping, internal audits, and external audits to secure their financials, businesses need to use a series of security processes to protect their networks.
Security processes are not a replacement for products; they're a way of using security products effectively. They can help mitigate the risks. Network security products will have flaws; processes are necessary to catch attackers exploiting those flaws, and to fix the flaws once they become public. Insider attacks will occur; processes are necessary to detect the attacks, repair the damages, and prosecute the attackers. Large systemwide flaws will compromise entire products and services (think digital cell phones, Microsoft Windows NT password protocols, or DVD); processes are necessary to recover from the compromise and stay in business.
Here are two examples of how to focus on process in enterprise network security:
1. Watch for known vulnerabilities. Most successful network-security attacks target known vulnerabilities for which patches already exist. Why? Because network administrators either didn't install the patches, or because users reinstalled the vulnerable systems. It's easy to be smart about the former, but just as important to be vigilant about the latter. There are many ways to check for known vulnerabilities. Network vulnerability scanners like Netect and SATAN test for them. Phone scanners like PhoneSweep check for rogue modems inside your corporation. Other scanners look for Web site vulnerabilities. Use these sorts of products regularly, and pay attention to the results.
2. Continuously monitor your network products. Almost everything on your network produces a continuous stream of audit information: firewalls, intrusion detection systems, routers, servers, printers, etc. Most of it is irrelevant, but some of it contains footprints from successful attacks. Watching it all is vital for security, because an attack that bypassed one product might be picked up by another. For example, an attacker might exploit a flaw in a firewall and bypass an IDS, but his attempts to get root access on an internal server will appear in that server's audit logs. If you have a process in place to watch those logs, you'll catch the intrusion in progress.
In this newsletter and elsewhere I have written pessimistically about the future of computer security. The future of computers is complexity, and complexity is anathema to security. The only reasonable thing to do is to reduce your risk as much as possible. We can't avoid threats, but we can reduce risk.
Nowhere else in society do we put so much faith in technology. No one has ever said, "This door lock is so effective that we don't need police protection, or breaking-and-entering laws." Products work to a certain extent, but you need processes in place to leverage their effectiveness.
A version of this essay originally appeared in the April issue of Information Security magazine.
You've probably been wondering what Counterpane has been doing since last summer. We've changed our name to Counterpane Internet Security, Inc. We're no longer providing consulting services. We've hired 95 people. The old Counterpane Systems has become Counterpane Labs, the research arm of the larger company. And we're addressing the real problems of computer security.
You never see a door lock advertised with the slogan: "This lock will prevent burglaries." In computer security, you see this kind of thing all the time. "Encryption prevents eavesdropping." "Firewalls prevent network penetration." "PKI prevents impersonation." It's actually not true.
When you buy a safe, it comes with a rating. "30TL" -- 30 minutes, tools. "60TLTR" -- 60 minutes, tools and torch. What this means is that a professional safecracker, with safecracking tools and an oxyacetylene torch, will need an hour to break open the safe. If the alarm doesn't sound, and guards don't come running, within that hour, the safe is worthless. All that safe buys you is time; you have to spend it wisely.
Prevention. Detection. Response. The computer-security industry has concentrated on protection, and has largely ignored detection and response. Intrusion-detection systems sound alarms, but unless there is someone to respond, it is no better than a car alarm that everyone ignores. This doesn't make sense.
If the protection mechanisms were perfect, you wouldn't need detection and response. If the safe could withstand safecrackers indefinitely, you wouldn't have to bother with alarms. If your firewalls never had any security bugs or were never misconfigured, if the encryption were always perfect, and if the PKI never had any vulnerabilities, you wouldn't need detection and response.
But no computer security product is perfect. Every day new security vulnerabilities are discovered in operating systems, server software, Internet applications, firewalls and other security devices. These products show no signs of getting more secure; if anything, the increasing complexity of the Internet is driving them towards being even less secure. You need detection and response.
Counterpane Internet Security, Inc. provides that detection and response. We're a managed security monitoring service. We don't replace your existing security products: your firewalls, VPNs, IDSs, PKIs, servers, routers. We love those products, and want them to get better and better. What we do is watch them.
We send their alerts to our trained security analysts, and contact you when we notice a security breach. We're your Internet alarm company. We augment your prevention products with a detection and response service. It's the only way to maintain security in today's networked world.
Counterpane Internet Security, Inc. does not sell security products; we only sell the service. We've realized that the fundamental problems in security are no longer about technology; they're about how to use the technology. Visit the Counterpane Web site; I look forward to explaining our company further.
Company Web site:
A white paper on what we're doing:
The importance of vigilance (written by Schneier):
Yet another classified laptop stolen, this time a U.S. State Department one:
And still more:
Intel is dropping the unique serial number in its microprocessors. This is good news, and Intel should be applauded for this move.
After almost two years of study, a secret committee of the German government has concluded that Internet attacks will supplant military conflicts in coming years.
An article on U.S. military security classifications:
No one was surprised when the Russian government said that they were going to eavesdrop on the Internet, but now the UK government wants to read your e-mail:
Interesting commentary on the "backdoor password" in Red Hat Linux.
A balanced, and skeptical, article on Echelon:
Yet another reason why it makes no sense to hide the lists of URLs that content filters filter:
Convicted hacker Kevin Mitnick was released from jail on probation a few months ago. Since then he's written for magazines, testified in front of Congress, and done various public speaking gigs. Suddenly his parole officer wants him to shut up. Mitnick responds, publicly:
More invasions of privacy on the way, this one via your ISP:
Good article on _Database Nation_:
<http://www.oreillynet.com/pub/a/network/2000/04/27/...> ...which is an excellent book (by the way).
More information on UCITA. The moral seems to be that it's smarter to spend your lobbying dollars at the state level than to risk it in an all-or-none federal bill. This whole thing is VERY dangerous.
Microsoft is touting biometrics as the solution to its security problems.
This announcement borders on ludicrous. Biometrics will do nothing to improve the general state of Windows security, and will have no effect on most of the security problems they have been suffering. And even on a good day, biometrics doesn't do what the industry proponents claim. See my other writing on the topic:
There's some news on the quantum cryptography front. I was not going to even bother mentioning this, but I have received enough press calls to indicate that most people don't understand the ramifications. As a scientist, I find this interesting. As a security professional, I know it's irrelevant. Elsewhere I've described a reliance on cryptography as putting a tall spike in the ground and hoping the enemy runs right into it. The real problems are not crypto-related: they're implementation errors, trust-model screw-ups, intentional misuse, misconfiguration, etc. Quantum cryptography is an interesting development, but it's akin to arguing whether the spike is one mile tall or 1.5 miles tall. (For anyone who's wondering what quantum cryptography is, there's a lucid explanation in the last chapter of Simon Singh's _The Code Book_.) Much more useful is to start worrying about all the non-crypto-related vulnerabilities.
I've long considered the lack of vendor liability to be one of the primary reasons the Internet is insecure. I also predicted a spate of lawsuits this year. Lawyers were trained in computers to prepare for the Y2K litigations, and they're bored. Here's a first inkling of what might come: one lawyer is suing US West because his DSL connection left his files exposed. As much as I don't like solving problems by litigation, he does have a point.
Excellent Village Voice story on the DeCCS DVD copy protection case:
President Clinton has signed a bill requiring law enforcement to document how frequently it intercepts encrypted conversations between suspected criminals.
<http://www.wired.com/news/politics/0,1283,36067,00.html> Clinton's statement:
<http://www.politechbot.com/docs/...> Wiretap stats from 1999:
Analyzing privacy policies: Major Web sites have privacy policies, right? Have you ever tried to read one of them? USA Today tried to, and failed.
A good introduction to IPSec:
Another essay on the open-source security debate:
The Council of Europe has released a draft of a proposed treaty on crime in cyberspace. (The Council of Europe consists of over 40 signatory nations, including the U.S., Canada, Japan, Russia, and South Africa.) While well-intentioned, it has a provision that could effectively cripple research.
The offending paragraph states:
> Article 6 Illegal Devices
> Each Party shall adopt such legislative and other measures as
> may be necessary to establish as criminal offences under its
> domestic law when committed intentionally and without right:
> a.the production, sale, procurement for use, import,
> distribution or otherwise making available of:
> 1.a device, including a computer program, designed
> or adapted [specifically] [primarily] [particularly] for the
> purpose of committing any of the offences established in
> accordance with Article 2
This would make it illegal to create, post, or download any piece of software that is "designed or adapted" to break into computer systems.
This is one of those "throwing the baby out with the bathwater" sorts of provisions.
Many legitimate computer-security tools -- vulnerability scanners, for example -- fall into this category. So does most of the computer-security research that discovers and fixes existing vulnerabilities. The effects of this treaty, if enforced, will only enable more insecure software.
I don't see how this law will affect the computer criminals. They're already distributing attack tools, and most of them do so anonymously. This will primarily affect legitimate computer-security research.
Microsoft has made its proprietary Kerberos extensions available, sort of.
You can download a document outlining the changes from the Microsoft Web site. However, the document is delivered as a self-extracting executable archive. But when you run the .exe, you are shown a license agreement that you must agree to to see the document. Here's the relevant paragraph:
"b. The Specification is confidential information and a trade secret of Microsoft. Therefore, you may not disclose the Specification to anyone else (except as specifically allowed below), and you must take reasonable security precautions, at least as great as the precautions you take to protect your own confidential information, to keep the Specification confidential. If you are an entity, you may disclose the Specification to your full-time employees on a need to know basis, provided that you have executed appropriate written agreements with your employees sufficient to enable you to comply with the terms of this Agreement."
What we have here is a way to distribute the spec while making it illegal to build compatible implementations. This completely defeats the IETF's interoperability goals, and helps Microsoft leverage their desktop monopoly into the server market.
Microsoft Web site:
It gets worse. It seems that there was a discussion of the Microsoft Kerberos specification on Slashdot. Some of this discussion violated the terms of the ridiculous license agreement above. So Microsoft sent Slashdot an angry lawyer letter, claiming that the postings were in violation of the DMCA (the Digital Millemium Copyright Act, the one that prohibits reverse-engineering). At this writing Slashdot has not removed the offending postings, but this could get ugly. My hope is that this acutally goes to court, and that some of the more bizarre provisions of the DMCA (and UCITA) get thrown out.
The thread Microsoft objects to:
Microsoft's lawyer letter and SlashDot's initial reply:
More SlashDot commentary:
Mirrored copy of the Kerberos specfication (live link at the time of writing):
Recently there has been a spate of news articles on client-side computer security topics. Several companies claim to sell e-mail security solutions where the e-mail cannot be read after a certain date, effectively "deleting" it. Other companies claim to sell rights-management software: audio and video files that can't be copied or redistributed, data that can be read but cannot be printed, software that can't be copied. The common thread in all of these "solutions" is that they postulate a situation where the owner of a file can control what happens to that file after it is sent to someone else.
It's complete nonsense.
Controlling what the client can do with a piece of data assumes a trusted (from the point of view of the initial owner of the file) piece of software running on the client. Such a thing does not exist, so these solutions don't work.
As an example, look at the on-line gaming community. Many games allow for multi-player interaction over the Internet, and some games even have tournaments for cash prizes. Hackers have written computer "bots" that assist play for some of these games, particularly Quake and NetTrek. The idea is that the bots can react much quicker than a human, and that the player becomes much more effective with the assistance of these bots. An arms race has ensued, as the game designers try to disable these bots and force fairer play, and the hackers make the bots cleverer.
These games are trying to rely on trusted client software, and the hacker community has managed to break every trick the game designers have thrown at them. I am continuously amazed by the efforts hackers will go through to break the security. The lessons are twofold: not only is there no reasonable way to trust a client-side program in real usage, but there's no possible way to ever achieve that level of protection.
Against all of these systems -- disappearing e-mail, rights management for music and videos, fair game playing -- there are two types of attackers: the average user and the skilled attacker. Against the average user anything works; there's no need for complex security software. Against the skilled attacker nothing works. And even worse, most systems need to be secure against the smartest attacker. If one person hacks Quake (or Intertrust or DisappearingInc), he can write a point-and-click software tool that anyone can use. Suddenly a security system that is secure against almost everyone can now be compromised by everyone.
Building a trusted client in software, and trying to limit the abilities of a user, on a general purpose computer is doomed to failure. For now, though, it provides a nice false sense of security.
What strikes me the most about this virus is how well it social engineers the user. It comes from someone the user knows. It has an enticing subject line. In Microsoft Outlook the ".vbs" extension is supressed by default, so it looks like an innocuous ".txt" file. Even with all the admonitions not to open attachments you're not expecting, the average user doesn't stand a chance against a virus like this.
Expect even worse in the future. Systems running either Microsoft Office 2000 or Internet Explorer 5.0 can be infected with these sorts of viruses even if the recipient doesn't open the attachment. That's right; if the system is running Internet Explorer with the default settings, it is vulnerable. The problem is
caused by a programming bug in an Internet Explorer ActiveX control. Thank you, Microsoft.
Back to the ILOVEYOU virus. Read James Gleick's excellent essay:
And Phil Agre's commentary is so perfect, I'm just going to reprint it here. You can subscribe to his newsletter, "Red Rock Eater News Service," at:
I received about 60 copies of the latest Microsoft e-mail virus and its variants. How many did you get? Fortunately I manage my e-mail with Berkeley mailx and Emacs keyboard macros, so I wasn't at risk. But if we're talking about billions of dollars in damage, which equates roughly to millions of lost work days, then I think that we and Microsoft need to have a little talk.
Reading the press reports, Microsoft's stance toward this situation has been disgraceful. Most of their sound bites have been sophistry designed to disassociate the company from any responsibility for the problem. One version goes like this quote from Scott Culp of Microsoft Public Relations, excuse me, I mean Microsoft Security Response Center:
This is a general issue, not a Microsoft issue. You can write a
virus for any platform. (New York Times 5/5/00)
Notice the public relations technology at work here: defocusing the issue so as to move attention away from the specific vulnerabilities of Microsoft's applications architecture and toward the fuzzy concept of "a virus". Technologists will understand the problem here, but most normal people will not. Mr. Culp also says this (CNET 5/5/00):
This is by-design behavior, not a security vulnerability.
More odd language. It's like saying, "This is a rock, not something that can fall to the ground". It's confusing to even think about it. Even though Microsoft had been specifically informed of the security vulnerability in its software, it had refused to fix it. Microsoft even tried to blame its problem on Netscape, which *had* fixed it:
The next step is to blame the users. The same Mr. Culp read on the radio the text of a warning that the users who spread the virus had supposedly ignored. That warning concludes with a statement to the effect that you shouldn't execute attachments from sources that you do not trust. He read that part kind of fast, as you might expect, given that the whole point of this virus is that people receive an attachment from a person who has included them in their address book. This particular blame-shifting tactic is particularly disingenuous given that the virus spread rapidly through Microsoft itself, to the point that the company had to block all incoming e-mail (Wall Street Journal 5/5/00).
Similarly, CNET (5/4/00) quoted an unnamed "Microsoft representative" as saying that companies must educate employees "not to run a program from an origin you don't trust". Notice the nicely ambiguous word "origin". The virus arrives in your mailbox clearly labeled as having been sent by a particular individual with whom you probably have an established relationship. It bears no other signs of its "origin" that an ordinary user will be able to parse, short of executing the attachment.
So what on earth is Microsoft doing allowing attachments to run code in a full-blown scripting language that can, among many other things, invisibly send e-mail? Says the "Microsoft representative",We include scripting technologies because our customers ask us to put them there, and they allow the development of business-critical productivity applications that millions of our customers use.
There needs to be a moratorium on expressions such as "customers ask us to". Does that mean all of the customers? Or just some of them? Notice the some/all ambiguity that is another core technology of public relations. Do these "customers" really specifically ask for fully general scripts that attachments can execute, or do they only ask for certain features that can be implemented in many ways, some of which involve attachments that execute scripts? Do the customers who supposedly ask for these crazy things understand the consequences of them? Do they ask for them to be turned on by default, so that every customer in the world gets the downside of them so that a few customers can more conveniently get the upside? And notice how the "Microsoft representative" defocuses the issue again, shifting from the specific issue of scripts that can be executed by attachments to the fuzzy concept of "scripting technologies", as if anybody were suggesting that scripting technologies, as such, in general, were to blame.
Microsoft shouldn't be broken up. It should be shut down.
Agre has even more examples of Microsoft doublespeak at:
From: David Wadsworth <dwadswetna.demon.co.uk>
Subject: Stolen Enigma Machine
Apparently the stolen machine was an Abwehr Enigma, as used by the German Intelligence service during the war. It does seem feasible that there are only three of these surviving in the world, they were taken better care of than the ordinary Enigmas, and the operators were more likely to destroy them to prevent capture. It was of particular interest to cryptographers, since it had two innovations: Firstly the fourth (reflecting) rotor stepped instead of being static, and each wheel stepped the next wheel several times per rotation instead of only once. The book "The Codebreakers" describes this machine in chapter 16, and suggests that BP would have had trouble breaking it if it wasn't for the fact that the Germans omitted the plug board which was used on the normal Enigmas.
From: David Jones <dejinode.org>
Subject: UCITA, remote self-help and implications for firewalls
UCITA in theory permits vendors to remotely disable software over the Internet. How, precisely, is this to be done?
All commercial enterprises that I know of that use commercial software have firewalls that prevent access to internal resources from outside. Even at home, I have my own LAN and a firewall.
In order for a vendor to be able to remotely disable software through the Internet, the vendor would need to access the software's license server, through the customer's firewall.
This opens up a number of issues. Vendors would have to document the protocols required to perform remote disable (e.g. what ports to use) so that customers could open up their firewalls. Vendors would need to ensure that customers indeed permit access, perhaps by requiring network licenses to be refreshed periodically. Different packages may have differing disable requirements. In the case of software that uses a common licensing technique (e.g. Globetrotter's FlexLM), the remote disable protocols may conflict with one another. (How many different license servers are running in your business?) Of course, vendors will likely also require that everyone do it the same way, since vendors won't want to keep track of which ports are used for each customer. As an I.T. director, would you want to handle all of this?
CRYPTO-GRAM is a free monthly newsletter providing summaries, analyses, insights, and commentaries on computer security and cryptography.
To subscribe, visit <http://www.schneier.com/crypto-gram.html> or send a blank message to email@example.com. To unsubscribe, visit <http://www.schneier.com/crypto-gram-faq.html>. Back issues are available on <http://www.counterpane.com>.
Please feel free to forward CRYPTO-GRAM to colleagues and friends who will find it valuable. Permission is granted to reprint CRYPTO-GRAM, as long as it is reprinted in its entirety.
CRYPTO-GRAM is written by Bruce Schneier. Schneier is founder and CTO of Counterpane Internet Security Inc., the author of "Applied Cryptography," and an inventor of the Blowfish, Twofish, and Yarrow algorithms. He served on the board of the International Association for Cryptologic Research, EPIC, and VTW. He is a frequent writer and lecturer on computer security and cryptography.
Counterpane Internet Security, Inc. is a venture-funded company bringing innovative managed security solutions to the enterprise.