Ricerc@Sapienza

In this work we focus on Power Analysis Attacks (PAAs) which exploit the dependence of the static current of sub- 50nm CMOS integrated circuits on the internally processed data. Spice level simulations of static current as a function of the input state have been carried out to show that static power consumption of nanometer logic gates continues to exhibit a strong dependence on input vector even for sub-50nm circuits and that the coefficient of variation for a nand gate is strongly increasing with the scaling of CMOS technology. We demonstrate that it is possible to recover the secret key of a cryptographic core by exploiting this data dependence by means of different statistical distinguishers. For the first time in the literature we formulate the Attack Exploiting Static Power (AESP) as a univariate attack by using the mutual information approach to quantify the information that leaks through the static power side channel independently from the adopted leakage model. This analysis shows that countermeasures conceived to protect cryptographic hardware from attacks based on dynamic power consumption (e.g. WDDL, MDPL, SABL) still exhibit a leakage through the static power side channel. Finally, we show that the Time Enclosed Logic (TEL) concept does not leak information through the static power (even in the worst case scenario in which the attacker can stop the clock signal) and is suitable to be used as a countermeasure against both attacks explointig dynamic power and attacks exploiting static power.