UPDATE: The keys are not in TZ. The bootloader is not unlockable, and we have the source of it now. In short, unless we find an exploit into ABOOT or into the Qualcomm stack itself to bypass the authentication altogether, even if we manage to flash some ramdon images we find they will not start. The boot process uses signature/certificate. There is NO key to be found in Vector. He is using asymetrical crypto. The only keys that exists are the private key of QC, and the private key of anki (they will never disclose them and there is no computational way to recover them). The updates ares encrypted with a plain text key (found) and the manifest.ini contains the hash of the images to be flashed. This manifest is then signed by another certificate (Anki only, self signed). During the update process the validity of the signature is verified with the public part of that certitficate (which is part of the system fs - the /anki/etc/ota.pub). At last, they are using dm-verity as a tamper/corruption detection against the filesystem it sefl (which is read only). The dm-verity hashes are stored in the cmdline param in the boot.img (signed if you've followed until then). ABOOT is patching that command line to set the correct partition number to verify. This thing is quite tough... but we are actively working around this!!