Latest Essays
Page 73
Web-Based Encrypted E-Mail
A version of this essay appeared on ZDNet.com.
The idea is enticing. Just as you can log onto Hotmail with your browser to send and receive e-mail, there are Web sites you can log on to to send and receive encrypted e-mail. HushMail, ZipLip, YNN-mail, ZixMail. No software to download and install…it just works.
But how well?
HushMail <http://www.hushmail.com> is basically a PGP or S/MIME-like e-mail application that uses Java (although oddly enough, HushMail is not compatible with either). The sender logs onto the HushMail Web site, and encrypts messages using a Java applet that is automatically downloaded onto his machine. Both the sender and receiver need to have HushMail accounts for this to work. Accounts can be anonymous…
NIST AES News
A version of this essay appeared on ZDNet.com.
AES is the Advanced Encryption Standard, the encryption algorithm that will eventually replace DES. In 1997, the U.S. government (NIST, actually), solicited candidate algorithms for this standard. By June 1998 (the submission deadline), NIST received fifteen submissions. NIST asked for comments on these algorithms, with the intention of pruning the list to five finalists. NIST held an AES conference in Rome in April (this was the second AES conference, the first was the previous August in California), the comment deadline was in June, and last Monday NIST announced the finalists…
Biometrics: Uses and Abuses
Biometrics are seductive. Your voiceprint unlocks the door of your house. Your iris scan lets you into the corporate offices. You are your own key. Unfortunately, the reality isn’t that simple.
Biometrics are the oldest form of identification. Dogs have distinctive barks. Cats spray. Humans recognize faces. On the telephone, your voice identifies you. Your signature identifies you as the person who signed a contract.
In order to be useful, biometrics must be stored in a database. Alice’s voice biometric works only if you recognize her voice; it won’t help if she is a stranger. You can verify a signature only if you recognize it. To solve this problem, banks keep signature cards. Alice signs her name on a card when she opens the account, and the bank can verify Alice’s signature against the stored signature to ensure that the check was signed by Alice…
Cryptography: The Importance of Not Being Different
Suppose your doctor said, “I realize we have antibiotics that are good at treating your kind of infection without harmful side effects, and that there are decades of research to support this treatment. But I’m going to give you tortilla-chip powder instead, because, uh, it might work.” You’d get a new doctor.
Practicing medicine is difficult. The profession doesn’t rush to embrace new drugs; it takes years of testing before benefits can be proven, dosages established, and side effects cataloged. A good doctor won’t treat a bacterial infection with a medicine he just invented when proven antibiotics are available. And a smart patient wants the same drug that cured the last person, not something different…
Why the Worst Cryptography is in the Systems that Pass Initial Analysis
Imagine this situation: An engineer builds a bridge. It stands for a day, and then collapses. He builds another. It stands for three days, and then collapses. Then, he builds a third, which stands for two weeks but collapses during the first rainstorm. So he builds a fourth. It’s been standing for a month, and has survived two rainstorms. Do you believe this fourth bridge is strong, secure and safe? Or is it more likely just another accident waiting to happen?
As bizarre as it may seem, this kind of design process happens all the time in cryptography, a field that is full of people who love to design their own algorithms and protocols. With so many aspiring cryptanalysts out there, however, there’s bound to be a lot of weak designs. The problem is this: Anyone, no matter how unskilled, can design an algorithm that he himself cannot break. Though a competent cryptanalyst can break most of this stuff after a short review, the rest of it survives, and in most cases is never looked at again (especially outside the military world). But just because an algorithm survives an initial review is no reason to trust it…
Intel's Processor ID
Last month Intel Corp. announced that its new processor chips would come equipped with ID numbers, a unique serial number burned into the chip during manufacture. Intel said that this ID number will help facilitate e-commerce, prevent fraud and promote digital content protection.
Unfortunately, it doesn’t do any of these things.
To see the problem, consider this analogy: Imagine that every person was issued a unique identification number on a national ID card. A person would have to show this card in order to engage in commerce, get medical care, whatever. Such a system works, provided that the merchant, doctor, or whoever can examine the card and verify that it hasn’t been forged. Now imagine that the merchants were not allowed to examine the card. They had to ask the person for his ID number, and then accept whatever number the person responded with. This system is only secure if you trust what the person says…
Security in the Real World: How to Evaluate Security
The following remarks are excerpted from a general session presentation delivered at CSI’s NetSec Conference in St. Louis, MO, on June 15th, 1999.
At Counterpane Systems, we evaluate security products and systems for a living. We do a lot of breaking of things for manufacturers and other clients. Over the years, I’ve built a body of lore about the ways things tend to fail. I want to share my “top 20 list” of what’s wrong with security products these days.
Cryptography is a really neat technology, because it allows us to take existing business and social constructs from the real world and move them into the world of computer networks. This is actually the big idea of cryptography. It doesn’t do anything new, it doesn’t do anything magical…
The 1998 Crypto Year-in-Review
1998 was an exciting year to be a cryptographer, considering all the developments in algorithms, attacks and politics. At first glance, the important events of the year seem completely unrelated: done by different people, at different times and for different reasons. But when we step back and reflect on the year-that-was, some common threads emerge—as do important lessons about the evolution and direction of cryptography.
New Algorithms
In June, the NSA declassified KEA and Skipjack. KEA is a public-key Key Exchange Algorithm, while Skipjack is a block cipher first used in the ill-fated Clipper Chip. The NSA wanted Fortezza in software, and the only way they could get that was to declassify both algorithms…
WORD IN EDGEWISE: Scrambled Message
Key recovery is like trying to fit a square peg into a round hole. No matter how much you finagle it, it's simply not going to work.
In the September issue of Information Security, Commerce Undersecretary William Reinsch suggests that U.S. crypto export policy hinges on the concept of “balance” (Q&A: “Crypto’s Key Man”).
For key recovery policy to be successful, he argues, it must achieve a balance between privacy and access, between the needs of consumers and the requirements of the law-enforcement community.
For those who have followed the key recovery debate, Reinsch’s comments will have a familiar ring. Ever since the Clipper chip first made headlines in 1993, the crypto community has debated the notion of key recovery (or key escrow, or data recovery, or trusted third party or any other marketing term used to describe the same concept)…
The Crypto Bomb Is Ticking
Today’s faster, less expensive computers can crack current encryption algorithms easier than ever before. So what’s next?
Cryptographic algorithms have a way of degrading over time. It’s a situation that most techies aren’t used to: Compression algorithms don’t compress less as the years go by, and sorting algorithms don’t sort slower. But encryption algorithms get easier to break; something that sufficed three years ago might not today.
Several things are going on. First, there’s Moore’s law. Computers are getting faster, better networked, and more plentiful. The table “Cracking for Dollars” on page 98 illustrates the vulnerability of encryption to computer power. Cryptographic algorithms are all vulnerable to brute force—trying every possible encryption key, systematically searching for hash-function collisions, factoring the large composite number, and so forth—and brute force gets easier with time. A 56-bit key was long enough in the mid-1970s; today that can be pitifully small. In 1977, Martin Gardner wrote that 129-digit numbers would never be factored; in 1994, one was…
Sidebar photo of Bruce Schneier by Joe MacInnis.