alt Hacker NewsSo that’s how in an event of war US adversaries will be relieved of their devices
> The anti-rollback mechanism uses Qfprom (Qualcomm Fuse Programmable Read-Only Memory), a region on Qualcomm processors containing one-time programmable electronic fuses.
What a nice thoughtful people to build such a feature.
That’s why you sanction the hell out of Chinese Loongson or Russian Baikal pity of CPU — harder to disable than programmatically “blowing a fuse”.
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This kind of thing is generally used to disallow downgrading the bootloader once there is a bug in chain of trust handling of the bootloader. Otherwise once broken is forever broken. It makes sense from the trusted computing perspective to have this. It's not even new, it was still there on p2k motorollas 25 years ago.
You may not want trusted computing and root/jailbreak everything as a consumer, but building one is not inherently evil.
There's so many ways to do this, but a simpler method is to hide a small logic block (somewhere in the 10 billion transistors of your CPU) that detects a specific, long sequence of bits and invokes the kill switch.
eFuses have been a thing forever on almost all MCUs/processors, and aren't some inherently "evil" technology - mostly they're used in manufacturing when you might have the same microcontroller/firmware on separate types of boards. I'm working on a board right now which is either an audio input or an output (depending on which components are fitted) and one or the other eFuse is burned to set which one it is, so subsequent firmware releases won't accidentally set a GPIO as an output rather than an input and potentially damage the device.