Key recovery against 3DES in CPU smart card based on improved correlation power analysis

The security of CPU smart cards, which are widely used throughout China, is currently being threatened by side-channel analysis. Typical countermeasures to side-channel analysis involve adding noise and filtering the power consumption signal. In this paper, we integrate appropriate preprocessing methods with an improved attack strategy to generate a key recovery solution to the shortcomings of these countermeasures. Our proposed attack strategy improves the attack result by combining information leaked from two adjacent clock cycles. Using our laboratory-based power analysis system, we verified the proposed key recovery solution by performing a successful correlation power analysis on a Triple Data Encryption Standard (3DES) hardware module in a real-life 32-bit CPU smart card. All 112 key bits of the 3DES were recovered with about 80 000 power traces.