HTC implemented robust security layers to prevent unauthorized flashing, leading to a "cat and mouse" game between HTC and the modding community.
Every HTC phone shipped with a "CID" stored in the bootloader. A generic unbranded phone had a CID of HTC__001 , while a T-Mobile device might have T-MOB010 . An RUU file would only flash if its internal CID list matched the device CID. This prevented users from flashing generic firmware onto carrier-locked devices. htc android phone rom update utility