I've been asked to improve the security of my company's iot device, and encrypt a storage partition. It's a general purpose arm based device, and currently can boot from a variety of sources (USB, network, sd card, etc).
The company wants to add a TPM chip to perform the partition encryption.
Am I right in thinking that a system lacking secure boot, that can boot whatever OS the user wants via network boot for example, could never be secure? I imagine the network booted OS could ask the TPM chip to decrypt the encrypted partition, showing that there's little actual security on this system.
Finally, if there's a uboot variant that uses a TPM chip to implement secure boot such as sboot, is that actually secure? I can't help but think that a system that allows any bootloader to run, would allow any security mechanism to be reverse engineered given enough time.