[microtonal]

For all practical purposes it's possible to do this. The boot ROM only boots a vendor-signed bootloader, the bootloader verifies the OS kernel, etc., until you have a fully verified boot chain. A secure enclave, which is completely separated from the main CPU and OS performs the attestation using a private key in its tamper-resistant storage and embeds the results of verification by the bootloader. There may be some vulnerabilities, but most of them can be fixed in updates, with exception of the boot ROM.

The reason why the system gets broken in Android occasionally is that most Android phones have terrible security and do not use a secure enclave/processor, etc. (which the iPhone had since 5s + Google/Samsung for quite some years through Titan M/Knox Vault). Instead they use TrustZone, which set up a TEE on the same CPU/RAM as the main OS. Of course, it uses memory protection for separation, but is often vulnerable to side-channel attacks. This is also the reason many Android phones will be cracked by Cellebrite in seconds (recently such a Mediatek TEE vulnerability was made public [1]).

[1] https://www.malwarebytes.com/blog/news/2026/03/this-android-...

[summm]

Nope. It is still not possible to give someone else (the government, or the bank) control over your phone while at the same time run software that you alone control with higher privileges. Please don't mix that up with "is practically hard to implement because of sloppy code. Also your attacker model is still "occasional evil government agency or evil private corporation wants to crack and read your messages", while what is discussed here is more fundamental "evil government or abusive corporation controls your phone in the first place, and can just remote control it you can't use really secure apps"

[whazor]

I want governments and banks to allow open-source software, not control my phone.

For example, I essentially trust the ROM I download from the GrapheneOS website. What I want is for governments, banks, or some independent open foundation to be able to approve that ROM too, so attestation can work with it.

More like how CA certificates work: not perfect, but not locked to one vendor either.

[summm]

So now you have the choice between two approved ROMs. Not a lot of improvement? And as soon as GrapheneOS implements something beneficial to the users that the government does not like, the approval will be taken back. That's also why GrapheneOS will probably not even think about doing that. So you want some OS functionality neither Google nor Graphene offer, you're, again, out of luck. CA is something completely different, and much more limited in what can be centrally controlled. Everybody can go to a CA, get a certificate for their domain, and use it with any server software, even with software they compiled themselves.