An Obfuscation Scheme Using Affine Transformation and Its Implementation

Abstract

Program analysis techniques have improved steadily over the past several decades, and these techniques have made algorithms and secret data contained in programs susceptible to discovery. Obfuscation is a technique to protect against this threat. Obfuscation schemes that encode variables have the potential to hide both algorithms and secret data. We define five types of attack — data-dependency attacks, dynamic attacks, instruction-guessing attacks, numerical attacks, and brute force attacks — that can be launched against existing obfuscation schemes. We then propose an obfuscation scheme which encodes variables in a code using an affine transformation. Our scheme is more secure than that of Sato, et al. because it can protect against dependency attacks, instruction-guessing attacks, and numerical attacks. We describe the implementation of our scheme as an obfuscation tool for C/C++ code.