Mixed Boolean-Arithmetic expressions are presented as a strong protection in the context of data flow obfuscation. As there is very little literature on the analysis of such obfus-cated expressions, two important subjects of interest are: to define what simplifying those expressions means, and how to design a simplification solution. We focus on evaluating the resilience of this technique, by giving theoretical elements to justify its efficiency and proposing a simplification algorithm using a pattern matching approach. The implementation of this solution is capable of simplifying the public examples of MBA-obfuscated expressions, demonstrating that at least a subset of MBA obfuscation lacks resilience against pattern matching analysis.