I nearly falafel my chair when I read about the Israeli researchers who've designed a device that can derive crypto keys from the unintentional radio signals emitted by a computer's CPU—and miniaturized it until it can fit into a pita.
Deriving keys by sniffing radio emissions from CPUs is a much-loved sport in the security research community, but this hack can do its mischief from 19" away — earlier versions had to be in physical contact with metal on the computer's case. The gadget cost $300 to prototype, and need not be disguised as a pita sandwich (it could pose as a trash-can, hotel phone, etc).
The researchers disclosed their findings to the GnuPG (GPG) project in advance, and there will be a new version of GPG that prevents the attack that comes out simultaneous with the paper, in September.
But the Tel Aviv researchers' technique uses that same form of radio spying to target a laptop—a far more electromagnetically complicated target than a key fob or a monitor—and also to do it on the cheap. The team cleverly reduced the resources necessary for their attack by sampling the radio emanations from the processor only intermittently, while the chip does its decryption work of reading those emissions at a much faster frequency. PITA takes its samples at 100 kiloherz compared with the processor's 20,000-times-faster computation rate of two gigaherz. But by tricking the target into decrypting a carefully chosen message, they were able to "twist the algorithm's arm" into leaking more sensitive information, creating more clues in the leaked emanations for their PITA radio to pick up.1
"It's like someone's reciting secrets in a room, and you only get to hear a syllable a day to try to reconstruct what they're saying," says Tromer. "You can force that person in the room to always say one syllable over and over if the secret is 'zero,' and another syllable over and over if the secret is 'one'…That allows us to take a very low frequency sample and still extract information."
This Radio Bug Can Steal Laptop Crypto Keys, Fits Inside a Pita [Andy Greenberg/Wired]
(Image: Falafel – Kamil's Kebabs QV AUD1, Alpha, CC-BY-SA)