readout protection bug https://www.aisec.fraunhofer.de/en/FirmwareProtection.html even level 2 can be circumvented by cheap tools on STM32F series

[WojtekP1]

The question - is it fixed on STM32G and C series?

[Bubbles]

Hi @Community member​,

it's modified - improved. However some weakness remain in design. It's still true that the RDP defaults to level 1 in case of mismatch. But that's actually a requirement.

Completely different protection was introduced with STM32H5, which is now certified with security labs, being probably the best secure GP MCU offer on the market.

BR,

J

[Pavel A.]

@JHOUD​ Is your reply about the F series only or also about L, G or H7?

Documentation on RDP level 2 says that it is like a fuse, this means that undoing level 2 should be physically impossible? Isn't this the requirement for level 2?

Apologies for jumping in.

[Bob S]

Also apologies for jumping in :)

My understanding is that RDP 2 is "like" a fuse as treated by the internal microcode/boot code. But it is not a physical fuse, just FLASH bits. The attack in the referenced document requires de-encapsulating the chip and exposing the die to strong UV-C light in an attempt to sufficiently change the gate charge on a FLASH cell in the OPTIONS RDP bits to flip at least 1 bit. That changes the RDP from level 2 to level 1. They then use other methods to extract code from RDP 1.

[S.Ma]

The usual fight and defense evolution level of any product. The level of defense grows with cost, and I guess most want security for free?