Government Computer News
Smart cards play it safe
Upcoming version of cryptographic standard tackles the emerging threat of power analysis
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Image: Rick Steele
KEEPING UP: Ray Snouffer says NIST has learned a lot about power analysis since the last standard, Federal Information Processing Standard 140-2, was approved in 2001.
“It’s going through our regular release review,” before being presented for a 90-day comment period, said Ray Snouffer, manager of the security testing and metrics group at the National Institute of Standards and Technology.
The third iteration of the standard, FIPS 140-3, contains the usual sorts of updates and clarifications that every maturing standard undergoes, but it also tackles a novel problem of growing concern — protecting smart cards from power analysis attacks. In those attacks, a hacker reads the power fluctuations in a working cryptographic module to crack its code.
Power analysis was a relatively new technique for cracking codes in single-chip processors when the last version of FIPS, FIPS 140-2, was approved in 2001, said Stan Kladko, director of the FIPS validation lab at BKP Security Labs. “At that time, there was not enough time to include it” in the standard.
Today, though, “this is one of the bread-and-butter attacks,” said Paul Kocher, president of Cryptography Research.
Power users
Power analysis was first described in 1999 by Kocher, along with researchers Joshua Jaffe and Benjamin Jun.
“Immediately, a number of smart cards were compromised,” Kladko said. All that is required is an oscilloscope, access to a smart card and reader, “and one week of work will get you the key.”
The hacker must get access to the power line source going into the chip or to an output pin to measure the power fluctuation. “The voltage in that pin will sag as power consumption increases,” Kocher said.
Feeding the voltage into an oscilloscope gives a visual output that can be correlated with the input and output of the processor. This is simple power analysis that works if you can get a simple one-to-one correlation between power consumption and the bits the processor is using.
If the correlation is not so simple, there is a more complex differential power analysis, which uses statistical analysis with a much larger group of measurements and statistical techniques to separate the signal from the noise and pull out the key.
Power analysis works with single-chip processors, including smart cards, and there are a growing number of government smart cards with cryptography. The Defense Department has issued more than 10 million Common Access Cards, and civilian agencies are supposed to be ramping up to replace millions more traditional identification cards with the Personal ID Verification smart card mandated in Homeland Security Presidential Directive 12.
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