RE: Hardware based downgrade protection with B0 and mcuboot

Hung Bui — Thu, 22 Oct 2026 12:44:53 GMT

Hi again,
Now I got what you are asking about. You are right , it's not supported if the NISB (B0) is used.
It's explained that bottom of the page I linked to:
https://nrfconnectdocs.nordicsemi.com/ncs/latest/nrf/app_dev/bootloaders_dfu/mcuboot_nsib/bootloader_downgrade_protection.html#downgrade-protection-using-nsib-with-mcuboot

The One Time Programmable (OTP) storage area has limited space and is designed to accommodate only one image. This design means that hardware downgrade protection can be used by the nRF Secure Immutable Bootloader or MCUboot, but not both simultaneously. When the nRF Secure Immutable Bootloader is enabled, MCUboot cannot utilize hardware downgrade protection. However, MCUboot can still use software downgrade protection even while hardware downgrade protection is active for the nRF Secure Immutable Bootloader.

You will have to use the software downgrade protection.

RE: Hardware based downgrade protection with B0 and mcuboot

Hung Bui — Thu, 22 Oct 2026 12:34:47 GMT

Hi Ramakrishnan,
Could you explain why you think downgrade protection is not applied when B0 is used ?
My understanding of MCUBOOT_HARDWARE_DOWNGRADE_PREVENTION is that it only apply to the first image (the application) and not to the second image (network core). The network core has its own mechanism running on the bootloader on the network core.

This is not related to B0.

If you want downgrade protection on B0 (meaning you can only update MCUBoot with equal or increased version) please take a look here: https://nrfconnectdocs.nordicsemi.com/ncs/latest/nrf/app_dev/bootloaders_dfu/mcuboot_nsib/bootloader_downgrade_protection.html#downgrade-protection-using-nsib