Using eFuses is a popular way of implementing downgrade prevention, but also for permanently disabling debug flags/interfaces in production hardware.

Some vendors (AMD) also use eFuses to permanently bond a CPU to a specific motherboard (think EPYC chips for certain enterprise vendors).

OnePlus just chose the hardware way, versus Apple the signature way

Whether for OnePlus or Apple, there should definitively be a way to let users sign and run the operating system of their choice, like any other software.

(still hating this iOS 26, and the fact that even after losing all my data and downgrading back iOS 18 it refused to re-sync my Apple Watch until iOS 26 was installed again, shitty company policy)

They don't want the hardware to be under your control. In the mind of tech executives, selling hardware does not make enough money, the user must stay captive to the stock OS where "software as a service" can be sold, and data about the user can be extracted.

Android's normal bootloader unlock procedure allows for doing so, but ensures that the data partition (or the encryption keys therefore) are wiped so that a border guard at the airport can't just Cellebrite the phone open.

Without downgrade protection, the low-level recovery protocol built into Qualcomm chips would permit the attacker to load an old, vulnerable version of the software, which has been properly signed and everything, and still exploit it. By preventing downgrades through eFuses, this avenue of attack can be prevented.

This does not actually prevent running custom ROMs, necessarily. This does prevent older custom ROMs. Custom ROMs developed with the new bootloader/firmware/etc should still boot fine.

This is why the linked article states:

> The community recommendation is that users who have updated should not flash any custom ROM until developers explicitly announce support for fused devices with the new firmware base.

Once ROM developers update their ROMs, the custom ROM situation should be fine again.

Realize that many of these manufacturers sell their hardware in and employ companies in highly policed societies. Just the fact that they are allowed to continue to operate implies that they are playing ball and may well have to perform a couple of favors. And that's assuming they are fully aware of what they are shipping, which may not be always the case.

I don't think it is a bad model at all to consider any cell phone to be compromised in multiple ways even though you don't have hard proof.

Pre-prod (etc.) devices will also have different fuses burnt.

But to answer your question: we know iPhones have a foolproof kill switch, it's a feature. Just mark your device as lost in Find My and it'll be locked until someone can provide your login details. Assuming it requires logging in to your Apple account (which it does, AFAIK; I don't think logging in to a local account is enough), this is the same as a remote kill switch; Apple could simply make a device enter this locked-down state and then tweak their server systems to deny logins.

My ownership is proved by my receipt from the store I bought it from.

This vandalization at scale is a CFAA violation. I'd also argue it is a fraudulent sale since not all rights were transferred at sale, and misrepresented a sale instead of an indefinite rental.

And its likely a RICO act, since the C levels and BOD likely knew and/or ordered it.

And damn near everything's wire fraud.

But if anybody does manage to take them to court and win, what would we see? A $10 voucher for the next Oneplus phone? Like we'd buy another.

Can you explain it in simpler terms such that an idiot like me can understand? Like what would an alternative OS have to do to be compatible with the "current eFuse states"?

There is when the device becomes hard bricked and triggers an unnecessary need for a new one.

[1] https://dontkillmyapp.com/oneplus

You may not want trusted computing and root/jailbreak everything as a consumer, but building one is not inherently evil.