Among side-channel attacks some exploit the timing behavior of IC while others exploit the power consumption or the EM emissions EMside channel efficiency is due to the inner properties ofEMemissions. Investigating Effects of Monetary Reward on Information Disclosure by Online Social Networks Users Their ability to propagate through different materials is the most striking one. Indeed, it allows attackers targeting the bounded hardware area integrating the crypto-module under attack or part of it. Investigating Effects of Monetary Reward on Information Disclosure by Online Social Networks Users This is all the more interesting because it allows getting round global hardware countermeasures against power analysis by focusing the analysis on reduced silicon die areas thanks to tiny probes. Investigating Effects of Monetary Reward on Information Disclosure by Online Social Networks Users Moreover, replacing the large probe of by the tiny one shown allows dividing the number of EM traces required to disclose the key of standard iterative Data Encryption Standard DES mapped into a field-programmable gate array FPGA. However, this requires localizing beforehand the crypto-module that may occupy onlya small fraction of the device area Investigating Effects of Monetary Reward on Information Disclosure by Online Social Networks Users However, focusing EM attacks, using small sensors, requires localizing leaking spots to overcome the quadratic increase with the square of package/probe sizes of the number of points to be attacked using either differential EM analyses DEMA or correlation EM analyses CEMA. Investigating Effects of Monetary Reward on Information Disclosure by Online Social Networks Users Within this context, the contribution of this paper is twofold. First, a localization technique based on spectral coherence analyses is introduced. It allows finding positions where EM attacks might be successful with a reduced set of traces. The technique, called weighted global magnitude squared incoherence WGMSI analysis, has several interesting properties. Investigating Effects of Monetary Reward on Information Disclosure by Online Social Networks Users First, it requires only few EM measurements to be efficiently applied. Investigating Effects of Monetary Reward on Information Disclosure by Online Social Networks Users Thirdly, this noninvasive and contactless technique can be applied even if the circuit under attack is encapsulated. The second contribution is a spectral coherence-based technique allowing performing successful DEMA with a reduced set of traces. This technique, which accelerates the convergence of DEMA based on difference of means DoM test, is denoted by differential global magnitude square incoherence DGMSI analysis afterward. This paper is organized as follows. Section II highlights the localization problem and gives details about the proposed localization technique.This section ends with experimental results demonstrating that WGMSI is efficient to localize the less robust positions against EMattacks. Section III highlights how Spectral Coherence can be furtherused to enhance DEMA based on DoM by reducing the number of traces to be collected and processed to disclose the secret key.Note that DoM is not the sole statistical test that can be used during an EM attack. Indeed there are many other tests; a classification of test is given in Conclusion is drawn in Section IV. WEIGHTED GLOBAL MAGNITUDE SQUARED INCOHERENCE Performing a DEMA, requires collecting a large number of traces. Itis thus time consuming even if the analysis is done at a single position above the device, with a large probe. The situation becomes unpractical when tiny sensors are used by an attacker or an evaluator aiming at demonstrating the robustness of a design against EM analyses.A. Problem Considering an iterative DES mapped onto an FPGA, one may plan collecting, at positions above and around the Spartan core displacement step of EM traces, using a diameter magnetic loop, to determine if EM emissions may be exploited or not.