A Practical Bare-Metal Secure Boot Kit for Cortex-M

What is secure boot ? Secure boot is one of those topics that sits at the intersection of embedded software, system security, and real products. Everyone has heard of it. Many projects mention it. Fewer actually implement it correctly — especially on bare-metal microcontrollers. This post does two things: Explains what secure boot really means on a bare-metal Cortex-M MCU Introduces a reference kit that demonstrates this flow end-to-end ⭐ If you’re a hobbyist or learner, this will help you understand why secure boot exists and how it works. ⭐ If you’re working on a serious prototype or early product, it will also show what a minimal, correct baseline looks like. What “secure boot” actually means on a bare-metal MCU At its core, secure boot answers one simple question: Should this firmware be allowed to run on this device? On a PC or smartphone, secure boot is handled by firmware layers, ROM code, and complex certificate chains. On a bare-metal Cortex-M MCU, you are responsible for that