I have a bootable flash disk and it contains customized Ubunto, I want to pass the flash disk to an unknown person and it has some security issues. I want to be sure an unknown person couldn't change flash disk contents. hence I want to calculate hash of flash content and verify it on each boot and prevent booting OS if the verification failed or the hash goes mismatch.
for this purpose, I should do bootloader programming, I looking for UEFI programming but I found a few documents and videos, And also I do not know whether to select UEFI or BIOS.
so I would appreciate you if you could help me and provide a Comprehensive solution or suggest any other solution(except bootloader programming) for my problem.