Provided are a method of updating firmware of a device, a device, and a mobile system including the device. The method includes: receiving, from a host, a first hash value and a signature, the first hash value corresponding to a firmware image at the host; performing a pre-verify operation for at least one of integrity verification and signature certification on the firmware image using the received first hash value and the received signature; receiving the firmware image from the host according to a result of the pre-verify operation; and obtaining a second hash value from the received firmware image to perform a post-verify operation for at least one of integrity verification and signature certification on the received firmware image.