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Added more info on distributions.
= Signals, Noise, and Statistics =
Before looking at the details of the template attack, it is important to understand the statistics concepts that are involved. A template is effectively a multivariate distribution that describes several key samples in the power traces. This section will describe what a multivariate distribution is and how it can be used in this context.
== Noise Distributions ==
Electrical signals are inherently noisy. Any time we take a voltage measurement, we don't expect to see a perfect, constant level. For example, if we attached a multimeter to a 5 V source and took 4 measurements, we might expect to see a data set like (4.95, 5.01, 5.06, 4.98). One way of modelling this voltage source is
so we're very unlikely to see a reading of 7 V. We'll use this to our advantage in this attack: if <math>f(x)</math> is very small for one of our subkey guesses, it's probably a wrong guess.
== Multivariate Statistics ==
''TODO: basics of multivariable stats''
= Profiling a Device =
= Points of Interest =