Pierre-Yvan Liardet

Leak Resistant Arithmetic

In this paper we show how the usage of Residue Number Systems (RNS) can easily be turned into a natural defense against many side-channel attacks (SCA). We introduce a Leak Resistant Arithmetic (LRA), and present its capacities to defeat timing, power (SPA, DPA) and electromagnetic (EMA) attacks.

Voltage Spikes on the Substrate to Obtain Timing Faults

Fault attacks are widely deployed against secure devices by hardware evaluation centers. While the least expensive fault injection techniques, like clock or voltage glitches, are well taken into account in secure devices by dedicated hardware counter-measures, more advanced techniques, such as light based attacks, require huge investments. This paper presents a new way to induce faults at a moderate cost that may defeat already in place hardware counter-measures. To demonstrate its effectiveness we applied this technique on an ASIC component. For this demonstration, fault exploitation is operated using the classic Bell core attack applied on a modular exponentiation supported by a modular arithmetic co-processor.

Random Euclidean Addition Chain Generation and Its Application to Point Multiplication

Efficiency and security are the two main objectives of every elliptic curve scalar multiplication implementations. Many schemes have been proposed in order to speed up or secure its computation, usually thanks to efficient scalar representation [30,10,24], faster point operation formulae [8,25,13] or new curve shapes [2]. As an alternative to those general methods, authors have suggested to use scalar belonging to some subset with good computational properties [15,14,36,41,42], leading to faster but usually cryptographically weaker systems. In this paper, we use a similar approach. We propose to modify the key generation process using a small Euclidean addition chain c instead of a scalar k. This allows us to use a previous scheme, secure against side channel attacks, but whose efficiency relies on the computation of small chains computing the scalar. We propose two different ways to generate short Euclidean addition chains and give a first theoretical analysis of the size and distribution of the obtained keys. We also propose a new scheme in the context of fixed base point scalar multiplication.

Collision Based Attacks in Practice

Chosen-Message Simple Power Analysis, also called Collision Based Attacks (CBA), have been proposed by Fouque, Yen and Homma. These attacks aim at inducing and detecting collisions during modular operations. However, detecting collisions is a challenging task in real environments. Doing it in an automated manner is even more challenging. In this paper, we propose and compare some methods and criteria allowing to automatically (without any visual inspection) detect the occurrence of collisions in leakage traces acquired on modern (and thus noisy) circuits.

Reverse engineering of embedded software using syntactic pattern recognition

When a secure component executes sensitive operations, the information carried by the power consumption can be used to recover secret information Many different techniques have been developped to recover this secret, but only few of them focus on the recovering of the executed code itself Indeed, the code knowledge acquired through this step of Simple Power Analysis (SPA) can help to identify implementation weaknesses and to improve further kinds of attacks In this paper we present a new approach improving the SPA based on a pattern recognition methodology, that can be used to automatically identify the processed instructions that leak through power consumption We firstly process a geometrical classification with chosen instructions to enable the automatic identification of any sequence of instructions Such an analysis is used to reverse general purpose code executions of a recent secure component.

From theory to practice: horizontal attacks on protected implementations of modular exponentiations

Nowadays, horizontal or single-shot side-channel attacks against protected implementations of RSA and similar algorithms constitute a theoretic threat against secure devices. Nevertheless, in practice their application remains very difficult not only because of their complexity, but also because of environmental countermeasures integrated by designers that render their application even more difficult. Horizontal side-channel attacks take place in multiple steps. Among them, the most important are the acquisition of a complete trace with a sufficiently high sampling rate, its cutting into regular patterns, the realignment of the obtained patterns, the reduction as far as possible of noise in the acquired trace, the identification of the points of interest and the application of an effective distinguisher. Each of these steps is crucial and leads, if performed without enough attention, to an unsuccessful attack. In this context, this paper introduces effective solutions to efficiently perform all these steps, i.e., practicable means for implementing efficient horizontal attacks.

Shape analysis for power signal cryptanalysis on secure components

Abstract: This paper presents an application of pattern recognition techniques in reverse engineering for smart cards. The aim of the study is to design algorithms based on shape classification and to determine instructions executed on a chip as well as processed data sets. Information is extracted from the power consumption in order to recover secret information. Then geometrical features are determined and a syntactic analysis is achieved in order to recover secret algorithms and data. Some examples are given showing how code execution can be reversed on a recent secure component. These examples are essentially focused on instruction recovery but the algorithms also work on data recovery or on a combination of both instruction and data recovery.