Even smarter cards

An IST team is developing secure chips designed to prevent would-be attackers cracking protective codes stored on smart cards using off-the-shelf technology.



‘It takes little more than an oscilloscope and a standard PC to mount a digital attack on an unprotected smartcard,’ said Klaus-Michael Koch, coordinator of the IST project SCARD.



Using techniques such as side-channel analysis (SCA), attackers can reveal part of a secret key. Methods include examining a chip’s power leakage as it performs computations or scrutinising its thermal or electromagnetic radiation.



To tackle leaky circuits, the SCARD partners developed two main countermeasures. The first introduced circuits with constant power consumption, irrespective of the tasks being performed. ‘Each clock cycle has the same energy. But these circuits must be perfectly executed, since even a three or four percent difference in energy can be seen,’ said Koch.



The second involved adding random values to the chip, masking the circuit’s real values. They also considered adding artificial noise, but this is not currently feasible in smartcards due to energy-loss restrictions.



The team also developed an eight-bit test chip, featuring both unprotected and protected versions of the same circuit. The chip includes a microcontroller, is fully programmable and has reduced leakage. It is also capable of resisting over 500,000 attempted measurements, as opposed to the 15,000-measurement threshold for an unprotected chip. As a result, researchers can for the first time directly compare the effect of certain countermeasures on unprotected or protected versions of the same circuit.



‘Our new chip is not one hundred percent secure,’ said Koch. ‘However, it is far more difficult to crack than existing unprotected versions and represents a quantum leap forward in security.’