Abstract. Side-channel attacks are a serious threat to implementations of cryptographic algorithms. Secret information is recovered based on power consumption, electromagnetic emanations or any other form of physical information leakage. Template attacks are probabilistic sidechannel attacks, which assume a Gaussian noise model. Using the maximum likelihood principle enables us to reveal (part of) the secret for each set of recordings (i.e., leakage trace). In practice, however, the major concerns are (i) how to select the points of interest of the traces, (ii) how to choose the minimal distance between these points, and (iii) how many points of interest are needed for attacking. So far, only heuristics were provided. In this work, we propose to perform template attacks in the principal subspace of the traces. This new type of attack addresses all practical issues in principled way and automatically. The approach is validated by attacking stream ciphers such as RC4. We also report analysis results of template style attacks against an FPGA implementation of AES Rijndael. Roughly, the template attack we carried out requires five time less encrypted messages than the best reported correlation attack against similar block cipher implementations.

We report the fabrication of enthalpy arrays and their use to detect molecular interactions, including protein-ligand binding, enzymatic turnover, and mitochondrial respiration. Enthalpy arrays provide a universal assay methodology with no need for specific assay development such as fluorescent labeling or immobilization of reagents, which can adversely affect the interaction. Microscale technology enables the fabrication of 96-detector enthalpy arrays on large substrates. The reduction in scale results in large decreases in both the sample quantity and the measurement time compared with conventional microcalorimetry. We demonstrate the utility of the enthalpy arrays by showing measurements for two proteinligand binding interactions (RNase A ؉ cytidine 2 -monophosphate and streptavidin ؉ biotin), phosphorylation of glucose by hexokinase, and respiration of mitochondria in the presence of 2,4-dinitrophenol uncoupler.U nderstanding the thermodynamics of molecular interactions is central to biology and chemistry. Although a number of methods are available, calorimetry is the only universal assay for the complete thermodynamic characterization of these interactions. Under favorable circumstances, the enthalpy, entropy, free energy, and stoichiometry of a reaction can be determined (1, 2). In addition, calorimetry does not require any labeling or immobilization of the reactants and hence offers a completely generic method for characterizing the interactions. Indeed, titration calorimetry is widely used in both drug discovery and basic science, but its use is severely constrained to a small number of very high-value measurements by the large sample requirements and long measurement times. No currently available methods for calorimetric measurements lend themselves to modern approaches in which large libraries of compounds, ranging from small molecules in combinatorial libraries to proteins and other macromolecules, are studied.Here we report a low-cost nanocalorimetry detector that can be used as a high-throughput assay tool to detect enthalpies of binding interactions, enzymatic turnover, and other chemical reactions. The detectors are made by using microscale fabrication technology, resulting in a nearly 3 orders of magnitude reduction in both the sample quantity and the measurement time over conventional microcalorimetry. The fabrication technology is low-cost and enables fabrication of 96-detector arrays, which we call enthalpy arrays, on large substrates. Accordingly, the technology will scale to high-volume production of disposable arrays. This increase in performance and reduction in cost promises to enable calorimetry to be used to investigate a substantial number of samples. Nanocalorimetry in the enthalpy array format has valuable applications in proteomics for protein interaction and protein chemistry research and in high-throughput screening and lead optimization for drug discovery. Materials and MethodsDevice Fabrication. The schematic cross section of a nanocalorimeter detector is shown in Fig. 1a. The d...

This paper presents analytical solutions for the effect of squeeze film damping on a MEMS torsion mirror. Both the Fourier series solution and the double sine series solution are derived for the linearized Reynold equation which is obtained under the assumption of small displacements. Analytical formulae for the squeeze film pressure variation and the squeeze film damping torque on the torsion mirror are derived. They are functions of the rotation angle and the angular velocity of the mirror. On the other hand, to verify the analytical modeling, the implicit finite difference method is applied to solve the nonlinear isothermal Reynold equation, and thus numerically determine the squeeze film damping torque on the mirror. The damping torques based on both the analytical modeling and the numerical modeling are then used in the equation of motion of the torsion mirror which is solved by the Runge-Kutta numerical method. We find that the dynamic angular response of the mirror based on the analytical damping model matches very well with that based on the numerical damping model. We also perform experimental measurements and obtain results which are consistent with those obtained from the analytical and numerical damping models. Although the analytical damping model is derived under the assumption of harmonic response of the torsion mirror, it is shown that with the air spring effect neglected, this damping model is still valid for the case of nonharmonic response. The dependence of the damping torque on the ambient pressure is also considered and found to be insignificant in a certain regime of the ambient pressure. Finally, the convergence of the series solutions is discussed, and an approximate one term formula is presented for the squeeze film damping torque on the torsion mirror.

Since their publication in 1998 and 2001 respectively, Power and Electromagnetic Analysis (SPA, DPA, EMA) have been successfully used to retrieve secret information stored in cryptographic devices. Both attacks usually model the side-channel leakages using the so-called "Hamming weight" and "Hamming distance" models, i.e. they only consider the number of bit transitions in a device as an image of its leakage. In these models, the main difference between power and electromagnetic analysis is assumed to be the fact that the latter allows space localization (i.e. to observe the leakage of only a part of the cryptographic device). In this paper, we make use of a more accurate leakage model for CMOS devices and investigate its consequences. In particular, we show that it is practically feasible to distinguish between 0 → 1 and 1 → 0 bit transitions in certain implementations and that electromagnetic analysis is particularly efficient in this respect. We denote this model as the "signed distance" leakage model and show how it may be very helpful to defeat some commonly used countermeasures (e.g. data buses precharged with random values). Then, we compare the different models and stress their respective constraints/advantages regarding practical attacks.