A data storage device including a non-volatile memory and a micro-controller is provided. The non-volatile memory stores a firmware file. The micro-controller is coupled to the non-volatile memory, and performs an encryption procedure on the firmware file. The encryption procedure includes: using a first key and a first algorithm to encrypt the firmware file to generate a signature, using the first key and a second algorithm to scramble the signature to generate a scrambled signature, and attaching the scrambled signature to the firmware file.