By definition, it could be more secure if people actually would be able to inspect it. Is it regardless the most secure? Hard to say. GrapheneOS is quite secure, probably more.
I for one am not comfortable with anyone having that much power over something that is supposed to be mine, so they are the same to me. Untrustable black boxes.
The signatures enable the update client to verify the releases and the firmware to verify the OS with the public key flashed by the user as part of installing the OS. Signed updates and verified boot fully work with any build of GrapheneOS following our build instructions. Auditor and AttestationServer also work once they're rebuilt with the new verified boot hash included.
This one is not really a fault of GrapheneOS, and more a reality that Android is not actually an open platform and never will be. I require a lot more control of a device I need to be able to trust than anything in the android ecosystem can offer anymore.
Replicant was the right approach but sadly never got the resources to pursue it at the required scale to support new devices.
You can litteraly build and sign GrapeheneOS yourself and you can audit it, if this is your concern. While in the chain of trust there is still Google Root key first, is this far away from "run any software they want on your device at any time, and even remotely brick it"
(and ofc you could also block updates on grapheneOS, which would also prevent this aswell)
And a black box is not something that you dont understand, applying that logic anything becomes a black box.
Also what setup are you using then ?
edit: and i mean i understand the idea of not trusting devices, but this is just a false equivalence. While at the same time, if you dont want to live with technology from like 100 years ago, at some point do you have to trust a black box, if you want to call it that.
GrapheneOS is 100% open source and supports reproducible builds. It is in no way a black box.
If you do not want anyone to hold your signing keys, you will need to stop using nearly all modern hardware and software.
This is not the fault of the Graphene team so much as a fundamental problem in the mobile chipset market.
Desktop/Laptop CPUs give you dramatically more control, especially with OpenSIL etc.
There are simply are no sovereign software solutions for modern mobile hardware.
The Linux distro I founded has zero blobs. Built completely from source and boots and runs on real laptops and desktops. That is what 100% open source looks like. Meanwhile every Android distro requires a vendor partition with dozens of black box blobs.