RP2350 Laser Attack: Ledger Donjon Re-Enables Debug
Here is your shopping list for reproducing this RP2350 attack: one RP2350-A4 chip pulled off its board and de-encapsulated, a focused infrared laser, specialised microscopy gear, and roughly $250,000 to pay for all of it. Ledger Donjon's security team did exactly that, and Raspberry Pi wrote up the findings.
What the researchers pulled off
RP2350 launched in August 2024 as Raspberry Pi's secure microcontroller, and the first of two Hacking Challenges went after its protections. Ledger Donjon mapped which spots on the die respond to a tightly aimed laser pulse. Hitting the right spots flipped specific register contents, which turned the debug interface back on for a chip that was meant to keep it locked, and that opened up OTP readout.
Why Raspberry Pi is not respinning the chip
The attack destroys the package, since the chip has to be removed and de-encapsulated first. If each device carries its own key, a stolen secret unlocks only that one unit. So A4 stays as it is. An earlier prizewinner, Courk, used a homebrew IR laser rig to glitch the older A2 stepping, and the boot ROM revision in A4 already closed that hole.
What it means for your own boards
- Secure boot and locked debug on the SWD pins (SWCLK and SWDIO) still stop casual probing.
- Give every board its own key rather than one shared secret across a whole batch.
- Treat the RP2350 datasheet security chapter as required reading before you ship anything.
The second Hacking Challenge, on side-channel analysis, is still unbeaten. A Pico 2 from circuit.rocks plus a logic analyser on a spare GPIO is enough to start measuring boot timing yourself. Read the full disclosure on the Raspberry Pi news page before you start.
Originally published on blog.circuit.rocks.
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