NXP, which makes the Mifare transit cards used in several countries, has sued Radboud University Nijmegen (in the Netherlands), to block publication of a research paper, "A Practical Attack on the MIFARE Classic," that is scheduled for publication at the ESORICS security conference in October. The new paper reportedly shows fatal security flaws in NXP's Mifare Classic, which appears to be the world's most commonly used contactless smartcard.

I wrote back in January about the flaws found by previous studies of Mifare. After the previous studies, there wasn't much left to attack in Mifare Classic. The new paper, if its claims are correct, shows that it's fairly easy to defeat MIFARE Classic completely.

It's not clear what legal argument NXP is giving for trying to suppress the paper. There was a court hearing last week in Arnheim, but I haven't seen any reports in the English-language press. Perhaps a Dutch-speaking reader can fill in more details. An NXP spokesman has called the paper "irresponsible" but that assertion is hardly a legal justification for censoring the paper.

Predictably, a document purporting to be the censored paper showed up on Wikileaks, and BoingBoing linked to it. Then, for some reason, it disappeared from Wikileaks, though BoingBoing commenters quickly pointed out that it was still available in Google's cache of Wikileaks, and also at Cryptome. But why go to a leak-site? The same article has been available on the Web all along at arxiv, a popular repository of sci/tech research preprints run by the Cornell University library.

[UPDATE (July 15): It appears that Wikileaks had the wrong paper, though one that came from the same Radboud group. The censored paper is called "Dismantling Mifare Classic".]

As usual in these cases of censorship-by-lawsuit, it's hard to see what NXP is trying to achieve with the suit. The research is already done and peer-reviewed,. The suit will only broaden the paper's readership. NXP's approach will alienate the research community. The previous Radboud paper already criticizes NXP's approach, in a paragraph written before the lawsuit:

We would like to stress that we notified NXP of our findings before publishing our results. Moreover, we gave them the opportunity to discuss with us how to publish our results without damaging their (and their customers) immediate interests. They did not take advantage of this offer.

What is really puzzling here is that the paper is not a huge advance over what has already been published. People following the literature on Mifare Classic – a larger group, thanks to the lawsuit – already know that the system is unsound. Had NXP reacted responsibly to this previous work, admitting the Mifare Classic problems and getting to work on migrating customers to newer, more secure products, none of this would have been necessary.

You've got to wonder what NXP was thinking. The lawsuit is almost certain to backfire: it will only boost the audience of the censored paper and of other papers criticizing Mifare Classic. Perhaps some executive got angry and wanted to sue the university out of spite. Things can't be comfortable in the executive suite: NXP's failure to get in front of the Mifare Classic problems will (rightly) erode customers' trust in the company and its products.

UPDATE (July 18): The court ruled against NXP, so the researchers are free to publish. See Mrten's comment below.

Yesterday the National Football League punished the New England Patriots and their coach, Bill Belichick, for videotaping an opposing team's defensive signals. The signals in question are used by coaches to tell their on-field defensive unit how to line up and which tactics to use for the next play. The coach typically makes hand signals and arm movements that the on-field players know how to interpret. (The offense also needs to send signals to players from the sidelines before each play, but they use radios.) The opposition gets an advantage if they know what play is coming, so they will try to figure out what the signals mean.

This is essentially a weak form of cryptography. The coaches apply a kind of encryption to translate the desired play into a ciphertext, which is a sequence of hand and arm movements. They transmit the ciphertext (by making the indicated movements) to the on-field players, who then decrypt it, recovering the original play that the coaches wanted to send. An adversary who can see the ciphertext is supposed to be unable to recover the original message.

I don't know what systems NFL teams use, but Belichick and the Patriots apparently thought they had a chance of breaking their opponents' code.

There's an interesting technical problem here: how to encrypt defensive plays into sideline signals securely, in a way that's practical for real coaches and players in a game situation. I can think of at least one solution that is secure and practical. (Exercise for geeky readers: How would you do this?)

You might think that any solution would be too complicated for a mere football player to decode. If you think that, you're underestimating the players involved. NFL defensive captains already cope with complex information and plans, and their teams' current signaling systems already require decoding of symbols. Clever solutions can be pretty simple.

Crypto applies not only to designing a team's signals, but also to analyzing rivals' signals. Who will be the first NFL team to hire a cryptographer?