Multi-Channel Leakage Detection Based on χ² Test of Independence

Side-channel analysis (SCA) is a critical tool for evaluating the security of cryptographic devices, as physical leakage can reveal sensitive information such as cryptographic keys. Multi-channel fusion attacks (MCFAs) have proven to be efficient in exploiting side-channel leakages. However, a crucial step before performing MCFA is to assess whether the leakages from different channels can be effectively fused. To address this, we propose a black-box approach based on the χ<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> test of independence to assess multi-channel leakage suitability for fusion. By treating the leakages as categorical variables, our method evaluates their association without requiring knowledge of the cryptographic key or device implementation.