Encryption as Evidence of Criminal Intent
An appeals court in Minnesota has ruled that the presence of encryption software on a computer may be viewed as evidence of criminal intent.
I am speechless.
Edited to add: The complete text is online.
Entries Tagged "cryptography"
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AES Timing Attack
Nice timing attack against AES.
For those of you who don’t know, timing attacks are an example of side-channel cryptanalysis: cryptanalysis using additional information about the inner workings of the cryptographic algorithm. I wrote about them here.
What’s the big idea here?
There are two ways to look at a cryptographic primitive: block cipher, digital signature function, whatever. The first is as a chunk of math. The second is a physical (or software) implementation of that math.
Traditionally, cryptanalysis has been directed solely against the math. Differential and linear cryptanalysis are good examples of this: high-powered mathematical tools that can be used to break different block ciphers.
On the other hand, timing attacks, power analysis, and fault analysis all makes assumptions about implementation, and uses additional information garnered from attacking those implementations. Failure analysis assumes a one-bit feedback from the implementation—was the message successfully decrypted—in order to break the underlying cryptographic primitive. Timing attacks assumes that an attacker knows how long a particular encryption operation takes.
SecurityFocus Interview
This is an interview with me from SecurityFocus.
The Potential for an SSH Worm
SSH, or secure shell, is the standard protocol for remotely accessing UNIX systems. It’s used everywhere: universities, laboratories, and corporations (particularly in data-intensive back office services). Thanks to SSH, administrators can stack hundreds of computers close together into air-conditioned rooms and administer them from the comfort of their desks.
When a user’s SSH client first establishes a connection to a remote server, it stores the name of the server and its public key in a known_hosts database. This database of names and keys allows the client to more easily identify the server in the future.
There are risks to this database, though. If an attacker compromises the user’s account, the database can be used as a hit-list of follow-on targets. And if the attacker knows the username, password, and key credentials of the user, these follow-on targets are likely to accept them as well.
A new paper from MIT explores the potential for a worm to use this infection mechanism to propagate across the Internet. Already attackers are exploiting this database after cracking passwords. The paper also warns that a worm that spreads via SSH is likely to evade detection by the bulk of techniques currently coming out of the worm detection community.
While a worm of this type has not been seen since the first Internet worm of 1988, attacks have been growing in sophistication and most of the tools required are already in use by attackers. It’s only a matter of time before someone writes a worm like this.
One of the countermeasures proposed in the paper is to store hashes of host names in the database, rather than the names themselves. This is similar to the way hashes of passwords are stored in password databases, so that security need not rely entirely on the secrecy of the database.
The authors of the paper have worked with the open source community, and version 4.0 of OpenSSH has the option of hashing the known-hosts database. There is also a patch for OpenSSH 3.9 that does the same thing.
The authors are also looking for more data to judge the extent of the problem. Details about the research, the patch, data collection, and whatever else thay have going on can be found here.
RFID Passport Security
According to a Wired article, the State Department is reconsidering a security measure to protect privacy that it previously rejected.
The solution would require an RFID reader to provide a key or password before it could read data embedded on an RFID passport’s chip. It would also encrypt data as it’s transmitted from the chip to a reader so that no one could read the data if they intercepted it in transit.
The devil is in the details, but this is a great idea. It means that only readers that know a secret data string can query the RFID chip inside the passport. Of course, this is a systemwide global secret and will be in the hands of every country, but it’s still a great idea.
It’s nice to read that the State Department is taking privacy concerns seriously.
Frank Moss, deputy assistant secretary for passport services, told Wired News on Monday that the government was “taking a very serious look” at the privacy solution in light of the 2,400-plus comments the department received about the e-passport rule and concerns expressed last week in Seattle by
participants at the Computers, Freedom and Privacy conference. Moss said recent work on the passports conducted with the National Institute of Standards and Technology had also led him to rethink the issue.“Basically what changed my mind was a recognition that the read rates may have actually been able to be more than 10 centimeters, and also recognition that we had to do everything possible to protect the security of people,” Moss said.
The next step is for them to actually implement this countermeasure, and not just consider it. And the step after that is for us to get our hands on some test passports to see if they’ve implemented it well.
The Doghouse: ExeShield
Yes, there are companies that believe that keeping cryptographic algorithms secret makes them more secure.
ExeShield uses the latest advances in software protection and encryption technology, to give your applications even more protection. Of course, for your security and ours, we won’t divulge the encryption scheme to anyone.
If anyone reading this needs a refresher on exactly why secret cryptography algorithms are invariably snake oil, I wrote about it three years ago.
The Doghouse: Xavety
It’s been a long time since I doghoused any encryption products. CHADSEA (Chaotic Digital Signature, Encryption, and Authentication) isn’t as funny as some of the others, but it’s no less deserving.
Read their “Testing the Encryption Algorithm” section: “In order to test the reliability and statistical independency of the encryption, several different tests were performed, like signal-noise tests, the ENT test suite (Walker, 1998), and the NIST Statistical Test Suite (Ruhkin et al., 2001). These tests are quite comprehensive, so the description of these tests are subject of separate publications, which are also available on this website. Please, see the respective links.”
Yep. All they did to show that their algorithm was secure was a bunch of statistical tests. Snake oil for sure.
More Hash Function Attacks
Here’s a pair of valid X.509 certificates that have identical signatures. The hash function used is MD5.
And here’s a paper demonstrating a technique for finding MD5 collisions quickly: eight hours on 1.6 GHz computer.
RFID Security Analysis
A very impressive analysis of the Texas Instruments RFID technology used in a variety of security systems, such as vehicle immobilizers and ExxonMobil’s SpeedPass system.
Mistake number 1: The cryptographic algorithm is a proprietary 40-bit cipher.
Flaw in Winkhaus Blue Chip Lock
The Winkhaus Blue Chip Lock is a very popular, and expensive, 128-bit encrypted door lock. When you insert a key, there is a 128-bit challenge/response exchange between the key and the lock, and when the key is authorized it will pull a small pin down through some sort of solenoid switch. This allows you to turn the lock.
Unfortunately, it has a major security flaw. If you put a strong magnet near the lock, you can also pull this pin down, without authorization—without damage or any evidence.
The worst part is that Winkhaus is in denial about the problem, and is hoping it will just go away by itself. They’ve known about the flaw for at least six months, and have done nothing. They haven’t told any of their customers. If you ask them, they’ll say things like “it takes a very special magnet.”
From what I’ve heard, the only version that does not have this problem is the model without a built-in battery. In this model, the part with the solenoid switch is aimed on the inside instead of the outside. The internal battery is a weak spot, since you need to lift a small lid to exchange it. So this side can never face the “outside” of the door, since anyone could remove the batteries. With an external power supply you do not have this problem, since one side of the lock is pure metal.
A video demonstration is available here.
Sidebar photo of Bruce Schneier by Joe MacInnis.