CMOS gates consume different amounts of power whether their output has a falling or a rising edge. Therefore the overall power consumption of a CMOS circuit leaks information about the activity of every single gate. This explains why, using differential power analysis (DPA), one can infer the value of specific nodes within a chip by monitoring its global power consumption only. We model the information leakage in the framework used by conventional cryptanalysis. The information an attacker can gain is derived as the autocorrelation of the Hamming weight of the guessed value for the key. This model is validated by an exhaustive electrical simulation.Our model proves that the DPA signal-to-noise ratio increases when the resistance of the substitution box against linear cryptanalysis increases.This result shows that the better shielded against linear cryptanalysis a block cipher is, the more vulnerable it is to side-channel attacks such as DPA.
Until 2009, Java Cards have been mainly threatened by Logical Attacks based on ill-formed applications. The publication of the Java Card 3.0 Connected Edition specifications and their mandatory on-card byte code verification may have then lead to the end of software-based attacks against such platforms. However, the introduction in the Java Card field of Fault Attacks, well-known from the cryptologist community, has proven this conclusion wrong. Actually, the idea of combining Fault Attacks and Logical Attacks to tamper with Java Cards appears as an even more dangerous threat. Although the operand stack is a fundamental element of all Java Card Virtual Machines, the potential consequences of a physical perturbation of this element has never been studied so far. In this article, we explore this path by presenting both Fault Attacks and Combined Attacks taking advantage of an alteration of the operand stack. In addition, we provide experimental results proving the practical feasibility of these attacks and illustrating their efficiency. Finally, we describe different approaches to protect the operand stack's integrity and compare their cost with a particular interest on the time factor.
Several types of logic gates suitable for leakage-proof computations have been put forward [1,2,3,4]. This paper describes a method, called "backend duplication" to assemble secured gates into leakage-proof cryptoprocessors. To the authors' knowledge, this article is the first CADoriented publication to address all the aspects involved in the backend design of secured hardware. The "backend duplication" method achieves the place-and-route of differential netlists. It allows for 100 % placement density and for balanced routing of dual-rail signals. Wires of every other metal layer are free to make turns. In addition, the method does not require any modification to the design rules passed to the router. The "backend duplication" method has been implemented in 0.13 µm ASIC technology and successfully tested on various ciphers. The example of the design of a DES module resistant against side-channel attacks is described into details.
At CHES 2001, Walter introduced the Big Mac attack against an implementation of rsa. It is an horizontal collision attack, based on the detection of common operands in two multiplications. The attack is very powerful since one single power trace of an exponentiation permits to recover all bits of the secret exponent. Moreover, the attack works with unknown or blinded input. The technique was later studied and improved by Clavier et alii and presented at INDOCRYPT 2012. At SAC 2013, Bauer et alii presented the first attack based on the Big Mac principle on implementations based on elliptic curves with simulation results.In this work, we improve the attack presented by Bauer et alii to considerably increase the success rate. Instead of comparing only two multiplications, the targeted implementation permits to compare many multiplications. We give experiment results with traces taken from a real target to prove the soundness of our attack. In fact, the experimental results show that the original Big Mac technique given by Walter was better that the technique given by Clavier et alii. With our experiments on a real target, we show that the theoretical improvements are not necessarily the more suitable methods depending on the targeted implementations.
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