Post-Quantum Overhead Lands Hardest on Low-End IoT Devices

Post-quantum cryptography adds overhead that most systems absorb without noticing, and that embedded and IoT deployments have to plan for explicitly. Integration is described as particularly challenging on low-end devices, where computational resources and processing power are limited by design rather than by oversight.

The overhead is not primarily arithmetic, which is the common misconception. Lattice-based schemes are computationally reasonable on modest cores. The pressure comes from size: keys and signatures substantially larger than their elliptic-curve equivalents have to fit in flash, pass through RAM during a handshake, and travel over a radio link that may be duty-cycle limited by regulation. On an LPWAN device sending a few dozen bytes per message, a signature measured in kilobytes is not a performance question but a feasibility one.

That is why the migration for constrained hardware is a design decision rather than a software update. A device already deployed with fixed flash and a bootloader that cannot be replaced has limited options regardless of what standards arrive. The teams with room to manoeuvre are the ones who left headroom deliberately, which is an argument for specifying more flash than today's firmware needs on any product expected to outlive the current decade.