The pixel has a TPM chip (Trusted Protection Module). This is a device that has an internal cryptographic key set that can never be accessed outside of a lab with access to the die, like using red fuming nitric acid to get to the die without damaging the gold bond wires – type/class of access.
The internal key of the device is used to create any additional keys you would like to make. It can also test the validity of any key it has generated and check the hash of any file. Hashing a file is ensuring it is unchanged using a key to ensure no one in the middle has altered or added to the file.
Graphene uses this TPM chip to create a chain of trust with the device. It is essentially like secure boot on a computer. Anyone with control over a key like this is able to make changes to your device.
No mobile devices contain documented hardware for the system on chip or the modem. Both of these are black boxes. Obviously the modem is a big concern. Google/Android is a scheme to make it as easy as possible for hardware manufacturers to build with Android using a kernel that only needs the hardware support binaries added at the last possible minute. There is no source code available for these binary kernel modules. The code is never added to the mainline Linux kernel. This is the mechanism used to deprecate your devices. These are orphaned kernels that are proprietary and cannot be properly maintained and updated because of these kernel modules for the physical hardware. The hardware is different enough that no one can reverse engineer it effectively and transfer that effort to other devices.
You can never completely trust this hardware. We simply do not know what is there and what it can do. However, with a TPM module, we can make it irrelevant and simply discard any interaction or activities we do not understand. We can also verify that none of this hardware is altering or interfering with the OS or files on the device. Any changes will alter the result of the files hash. The inability to access or modify the TPM hidden key and its existence outside of the SoC is the reason Pixels are used and why other devices are insecure.
I was interested in using GrapheneOS but didn’t fully understand why the devs trust Google. turns out they don’t have to! thanks for the great explanation!
The pixel has a TPM chip (Trusted Protection Module). This is a device that has an internal cryptographic key set that can never be accessed outside of a lab with access to the die, like using red fuming nitric acid to get to the die without damaging the gold bond wires – type/class of access.
The internal key of the device is used to create any additional keys you would like to make. It can also test the validity of any key it has generated and check the hash of any file. Hashing a file is ensuring it is unchanged using a key to ensure no one in the middle has altered or added to the file.
Graphene uses this TPM chip to create a chain of trust with the device. It is essentially like secure boot on a computer. Anyone with control over a key like this is able to make changes to your device.
No mobile devices contain documented hardware for the system on chip or the modem. Both of these are black boxes. Obviously the modem is a big concern. Google/Android is a scheme to make it as easy as possible for hardware manufacturers to build with Android using a kernel that only needs the hardware support binaries added at the last possible minute. There is no source code available for these binary kernel modules. The code is never added to the mainline Linux kernel. This is the mechanism used to deprecate your devices. These are orphaned kernels that are proprietary and cannot be properly maintained and updated because of these kernel modules for the physical hardware. The hardware is different enough that no one can reverse engineer it effectively and transfer that effort to other devices.
You can never completely trust this hardware. We simply do not know what is there and what it can do. However, with a TPM module, we can make it irrelevant and simply discard any interaction or activities we do not understand. We can also verify that none of this hardware is altering or interfering with the OS or files on the device. Any changes will alter the result of the files hash. The inability to access or modify the TPM hidden key and its existence outside of the SoC is the reason Pixels are used and why other devices are insecure.
I was interested in using GrapheneOS but didn’t fully understand why the devs trust Google. turns out they don’t have to! thanks for the great explanation!