Symbol p_i

The passage around this formula

Here is the modelling error to avoid. Suppose a request passes n independent detection layers, each of which fails to catch a given malicious input with probability $p_i$ . It is tempting to write the bypass probability of the stack as $P_{\mathrm{bypass}} = \prod_{i=1}^{n} p_i$. and conclude that four layers at ten percent leakage each give one bypass in ten thousand. That number is an artefact of the independence assumption, and the assumption is the weakest part of the model. The…

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