Nokia Citrix UK National Cyber Security Centre PQShield This document provides guidance on integrating Post-Quantum Cryptography (PQC) into resource-constrained devices, such as IoT nodes and lightweight Hardware Security Modules (HSMs). These systems often operate with strict limitations on processing power, RAM, and flash memory, and may even be battery-powered. The document emphasizes the role of hardware security as the basis for secure operations, supporting features such as seed-based key generation to minimize persistent storage, efficient handling of ephemeral keys, and the offloading of cryptographic tasks in low-resource environments. It also explores the implications of PQC on firmware update mechanisms in such constrained systems.