Univariate side channel attacks and leakage modeling

Abstract

Differential power analysis is a powerful cryptanalytic technique that exploits information leaking from physical implementations of cryptographic algorithms. During the two last decades, numerous variations of the original principle have been published. In particular, the univariate case, where a single instantaneous leakage is exploited, has attracted much research effort. In this paper, we argue that several univariate attacks among the most frequently used by the community are not only asymptotically equivalent, but can also be rewritten one in function of the other, only by changing the leakage model used by the adversary. In particular, we prove that most univariate attacks proposed in the literature can be expressed as correlation power analyses with different leakage models. This result emphasizes the major role plays by the model choice on the attack efficiency. In a second point of this paper, we hence also Research associate of the Belgian Fund for Scientific Research (FNRS-F.R.S.). J. Doget (B) · E. Prouff Oberthur Technologies, 71-73 rue des Hautes Pâtures, discuss and evaluate side channel attacks that involve no leakage model but rely on some general assumptions about the leakage. Our experiments show that such attacks, named robust, are a valuable alternative to the univariate differential power analyses. They only loose bit of efficiency in case a perfect model is available to the adversary, and gain a lot in case such information is not available.

Behind the Scene of Side Channel Attacks

“…This study was motivated by the observation that the classical LRA distinguisher value for one leakage time is not comparable as such to that computed for another leakage time. Figure 1(a) illustrates this claim for an LRA targeting the device B described in Section 2.5: when directly applying the protocol given in [11,31], the correct key candidate does not maximize the distinguisher value globally but only in a local area, which makes the attack unsuccessful unless this area is known by the adversary (which is not assumed here). This observation led us to study the handling of distinguishing values in SCA attacks.…”

“…More generally, our study relies on a well studied problem which is the comparison of the results of two different instantaneous attacks [11,20,33,34,36,38]. For the LRA, it will lead to a modification of the candidate selection rule.…”

“…the highest correlation coefficient in a Correlation Power Analysis -CPA- [8]). Nevertheless we argue that this strategy can be ineffective for some attack categories, including the case of the Linear Regression Analysis (LRA) [11,30,31]. For the latter one, we propose a new strategy to select the most likely candidate and we demonstrate its effectiveness in practice.…”

“…Initially, they were presented with a profiling step and were viewed as an alternative to the template attacks [13]. In [11], the authors have shown how to express the linear regression attacks such that the profiling stage is no longer required. They also argued that the LRA can be applied in the same context as the CPA, but with weaker assumption on the device behavior.…”

“…[8,9,11,12,31]). In order to to compare and classify them, theoretical frameworks have then been introduced [11,22,35,39]. Their main purpose is to identify the attacks similarities and differences, and to exhibit contexts where one is better than another.…”