CASI: Compression-Based Structural Integrity Analysis for Cryptographic Validation

Abstract

CASI is a universal permutation-normalized exchangeability test for detecting residual structure in byte streams. CASI=1.0 means pseudorandom, CASI>1.5 means detectable structure. IEEE-validated at ICECET 2026. Characterizes all three NIST PQC standards (ML-KEM, ML-DSA, HQC). The compress_d function in ML-KEM masks the LWE distributional signature. Available as live-casi on PyPI.