Byon August 7, 2008 10:59 AM
<p>The <a href="http://www.blackhat.com/">Blackhat</a> conference was running this week, and a large number of interesting security issues were raised (even if <a href="http://www.fiercecio.com/story/black-hat-presentation-apple-cancelled-last-minute/2008-08-05">Apple wouldn’t let their devs talk</a>), but one that I found interesting was the discussion of the FasTrak system. FasTrak is a automated Toll paying system used California’s large cities that have toll booths on their major motorways. Researcher <a href="http://www.root.org/~nate/">Nate Lawson of Root Labs</a> discovered that the FastTrak, which I suspect is very similar to New York City’s FastPass system, uses no Authentication, and simply replies with it’s RFID signal to anyone who scan it.</p>
Anyone who’s read Cory Doctorow’s Little Brother will find this familiar. Especially when matched with the next step. Unauthenticated over-the-air upgrading. That’s right, you can change the value of the chip without actually handling the chip. Awesome.
So, what’s this mean? Well, the unauthenticated read allows anyone with a reasonably powerful RFID reader to track anyone with a FasTrak in their car from any location. In Little Brother, the Department of Homeland Security (DHS) uses this system to track people all over the streets of San Francisco. And as bad as it would be for the Government to do something that broad, this system allows anyone who wants to track individual vehicles easily throughout California.
And the unauthenticated update? This makes it trivial to travel for free, as you can easily steal a valid FasTrak code, and re-flash your own FasTrak and travel on someone elses dime. This allows people who have interest in masking their movements to change their FasTrak codes frequently, so that they can not be tracked via FasTrak. Really want to create mayhem? Do what Marcus and the other Little Brothers did, and start just randomly flashing people’s FasTraks.
RFID is an inherently untrusted protocol. It gladly responds to anyone who asks for it’s code, and by default it doesn’t have any method to authenticate even for writes. Over-the-air writes are a dangerous idea in the first place. If someone really needs to recode their pass, they should have no problem taking it somewhere to be safely re-written over a wire, preferably using encryption to verify that the new code was authorized. Over-the-air reads, a fantastically useful thing, should require a strong challenge. This is much harder, though it could be implemented using something like a simple counter and encryption so that the signal is encrypted and can only be decrypted by the software with the other half of the key. It’s harder, and it’s more expensive, but it’s far far safer.
In addition to FasTrak falling apart, the Mifare cards created by NXP Semiconductors, and used for London’s transit among many other systems, has been found to have similar exploits. Bruce Schneier already has a fantastic write up on this on his blog, particularly NXP’s attempt to suppress the researchers who uncovered the flaws.
Security is hard, really hard. It constantly needs to be fixed and updated, but there are certain things that should be so obviously wrong, like RFID update over-the-air, that I can’t believe people base entire businesses on obviously flawed systems. Still, consumers have a right to know, and researchers have a right to research. Plus, by the time the researchers have figured it out and published, there is always a good chance that someone else has already figured it out to, and has been exploiting it for their own gain.