TL;DR

— Photon-emission microscopy allowed us to locate a register responsible for the enabling of debug features on the Raspberry Pi microcontroller.

— Laser pulses at two nearby positions then restored debugger access to the chip’s Secure world, even though debug had been permanently disabled.

— Using that access after a rescue reset, we recovered a secret from one-time-programmable memory. The reset halted the chip before firmware could apply its runtime lock, so the page stayed Secure-readable.

— The attack requires physical access, destructive preparation, and approximately $250,000 of laboratory equipment.

The RP2350 security model

The RP2350 is Raspberry Pi’s dual-core microcontroller: each processor socket can select either an Arm Cortex-M33 or a RISC-V Hazard3 core at boot.…