Entropy-Driven Inconsistencies in Shared Secrets with CRYSTALS-Kyber on Heterogeneous Platforms

Post-Quantum Cryptography (PQC) is essential to secure future Internet-of-Things (IoT) systems against quantum adversaries. CRYSTALS-Kyber, recently standardized by NIST, provides efficient key encapsulation for constrained devices. This paper investigates Kyber’s interoperability across heterogeneous IoT platforms—Raspberry Pi, ESP32, and x86-64 laptops—using the MQTT protocol. We demonstrate successful key exchanges among homogeneous platforms and mixed Raspberry Pi–laptop systems, but observe failures in ESP32 cross-platform exchanges. Analysis indicates that inconsistent shared secrets originate from entropy variations in platform-specific Random Number Generators (RNGs). Our results highlight the need for standardized entropy handling in PQC implementations for seamless IoT integration.