April 27, 2017

Archives for January 2008

MySpace Photos Leaked; Payback for Not Fixing Flaw?

Last week an anonymous person published a file containing half a million images, many of which had been gathered from private profiles on MySpace. This may be the most serious privacy breach yet at MySpace. Kevin Poulsen’s story at Wired News implies that the leak may have been deliberate payback for MySpace failing to fix the vulnerability that allowed the leaks.

“I think the greatest motivator was simply to prove that it could be done,” file creator “DMaul” says in an e-mail interview. “I made it public that I was saving these images. However, I am certain there are mischievous individuals using these hacks for nefarious purposes.”

The MySpace hole surfaced last fall, and it was quickly seized upon by the self-described pedophiles and ordinary voyeurs who used it, among other things, to target 14- and 15-year-old users who’d caught their eye online. A YouTube video showed how to use the bug to retrieve private profile photos. The bug also spawned a number of ad-supported sites that made it easy to retrieve photos. One such site reported more than 77,000 queries before MySpace closed the hole last Friday following Wired News’ report.

MySpace plugged a a href=”http://grownupgeek.blogspot.com/2006/08/myspace-closes-giant-security-hole.html”>similar security hole in August 2006 when it made the front page of Digg, four months after it surfaced.

The implication here, not quite stated, is that DMaul was trying to draw attention to the flaw in order to force MySpace to fix it. If this is what it took to get MySpace to fix the flaw, this story reflects very badly on MySpace.

Anyone who has discovered security flaws in commercial products knows that companies react to flaws in two distinct ways. Smart companies react constructively: they’re not happy about the flaws or the subsequent PR fallout, but they acknowledge the truth and work in their customers’ interest to fix problems promptly. Other companies deny problems and delay addressing them, treating security flaws solely as PR problems rather than real risks.

Smart companies have learned that a constructive response minimizes the long-run PR damage and, not coincidentally, protects customers. But some companies seem to lock themselves into the deny-delay strategy.

Now suppose you know that a company’s product has a flaw that is endangering its customers, and the company is denying and delaying. There is something you can do that will force them to fix the problem – you can arrange an attention-grabbing demonstration that will show customers (and the press) that the risk is real. All you have to do is exploit the flaw yourself, get a bunch of private data, and release it. Which is pretty much what DMaul did.

To be clear, I’m not endorsing this course of action. I’m just pointing out why someone might find it attractive despite the obvious ethical objections.

The really interesting aspect of Poulsen’s article is that he doesn’t quite connect the dots and say that DMaul meant to punish MySpace. But Poulsen is savvy enough that he probably wouldn’t have missed the implication either, and he could have written the article to avoid it had he wanted to. Maybe I’m reading too much into the article, but I can’t help suspecting that DMaul was trying to punish MySpace for its lax security.

New $2B Dutch Transport Card is Insecure

The new Dutch transit card system, on which $2 billion has been spent, was recently shown by researchers to be insecure. Three attacks have been announced by separate research groups. Let’s look at what went wrong and why.

The system, known as OV-chipkaart, uses contactless smart cards, a technology that allows small digital cards to communicate by radio over short distances (i.e. centimeters or inches) with reader devices. Riders would carry either a disposable paper card or a more permanent plastic card. Riders would “charge up” a card by making a payment, and the card would keep track of the remaining balance. The card would be swiped past the turnstile on entry and exit from the transport system, where a reader device would authenticate the card and cause the card to deduct the proper fare for each ride.

The disposable and plastic cards use different technologies. The disposable card, called Mifare Ultralight, is small, light, and inexpensive. The reusable plastic card, Mifare Classic, uses more sophisticated technologies.

The first attack, published in July 2007, came from Pieter Sieckerman and Maurits van der Schee of the University of Amsterdam, who found vulnerabilities in the Ultralight system. Their main attacks manipulated Ultralight cards, for example by “rewinding” a card to a previous state so it could be re-used. These attacks looked fixable by changing the system’s software, and Sieckerman and van der Schee described the necessary fixes. But it was also evident that a cleverly constructed counterfeit Ultralight card would be able to defeat the system in a manner that would be very difficult to defense.

The fundamental security problem with the disposable Ultralight card is that it doesn’t use cryptography, so the card cannot keep any secrets from an attacker. An attacker who can read a card (e.g., by using standard equipment to emulate a card reader) can know exactly what information is stored on the card, and therefore can make another device that will behave identically to the card. Except, of course, that the attacker’s device can always return itself to the “fully funded” state. Roel Verdult of Raboud University implemented this “cloning” attack and demonstrated it on Dutch television, leading to the recent uproar.

The plastic Mifare Classic card does use cryptography: legitimate cards contain secret keys that they use to authenticate themselves to readers. So attackers cannot straightforwardly clone a card. Mifare Classic was designed to use a secret encryption algorithm.

Karsten Nohl, “Starbug,” and Henryk Plötz announced an attack that involved opening up a Mifare Classic card and capturing a high-resolution image of the circuitry, which they then used to reverse-engineer the cryptographic algorithm. They didn’t publish the algorithm, but their work shows that a real attacker could get the algorithm too.

Unmasking of the algorithm should have been no problem, had the system been engineered well. Kerckhoffs’s Principle, one of the bedrock maxims of cryptography, says that security should never rely on keeping an algorithm secret. It’s okay to have a secret key, if the key is randomly chosen and can be changed when needed, but you should never bank on an algorithm remaining secret.

Unfortunately the designers of Mifare Classic did not follow this principle. Instead, they chose to combine a secret algorithm with a relatively short 48-bit key. This is a problem because once you know the algorithm it’s possible for an attacker to search the entire 48-bit key space, and therefore to forge cards, in a matter or days or weeks. With 48 key bits, there are only about 280 trillion possible keys, which sounds like a lot to the person on the street but isn’t much of a barrier to today’s computers.

Now the Dutch authorities have a mess on their hands. About $2 billion have been invested in this project, but serious fraud seems likely if it is deployed as designed. This kind of disaster would have been less likely had the design process been more open. Secrecy was not only an engineering mistake (violating Kerckhoffs’s Principle) but also a policy mistake, as it allowed the project to get so far along before independent analysts had a chance to critique it. A more open process, like the one the U.S. government used in choosing the Advanced Encryption Standard (AES) would have been safer. Governments seem to have a hard time understanding that openness can make you more secure.

Could Use-Based Broadband Pricing Help the Net Neutrality Debate?

Yesterday, thanks to a leaked memo, it came to light that Time Warner Cable intends to try out use-based broadband pricing on a few of its customers. It looks like the plan is for several tiers of use, with the heaviest users possibly paying overage charges on a per-byte basis. In confirming its plans to Reuters, Time Warner pointed out that its heaviest-using five percent of customers generate the majority of data traffic on the network, but still pay as though they were typical users. Under the new proposal, pricing would be based on the total amount of data transferred, rather than the peak throughput on a connection.

If the current, flattened pricing is based on what the connection is worth to a typical customer, who makes only limited use of the connection, then the heaviest five percent of users (let’s call them super-users as shorthand) are reaping a surplus. Bandwidth use might be highly elastic with respect to price, but I think it is also true that the super users do reap a great deal more benefit from their broadband connections than other users do – think of those who pioneer video consumption online, for example.

What happens when network operators fail to see this surplus? They have marginally less incentive to build out the network and drive down the unit cost of data transfer. If the pricing model changed so that network providers’ revenue remained the same in total but was based directly on how much the network is used, then the price would go down for the lightest users and up for the heaviest. If a tiered structure left prices the same for most users and raised them on the heaviest, operators’ total revenue would go up. In either case, networks would have an incentive to encourage innovative, high-bandwidth uses of their networks – regardless of what kind of use that is.

Gigi Sohn of Public Knowledge has come out in favor of Time Warner’s move on these and other grounds. It’s important to acknowledge that network operators still have familiar, monopolistic reasons to intervene against traffic that competes with phone service or cable. But under the current pricing structure, they’ve had a relatively strong argument to discriminate in favor of the traffic they can monetize, and against the traffic they can’t. By allowing them to monetize all traffic, a shift to use based pricing would weaken one of the most persuasive reasons network operators have to oppose net neutrality.