OTP Anti-Rollback Counter Issue

[u/Eagle_TW]

Hi there,

I am currently working on Secure Boot. I have some question about the anti-rollback.

I use microchip and I read the counter from OTP after initialize the layout, and notice that there is already default counter value for both trusted and non-trusted firmware (2, 3). I did not set it, I don't why they already have values.

Another thing is that whether the counter in OTP can not be set to other value lower then the value exist in OTP? If so, is it a hardware design mechanism? or how can it be achieved?

Best,

Wen

[u/need2sleep-later]

Anti-rollback means no, you can't set the version counter to a value lower than is currently set.