Do it like AAA games that disallow modifications. They ship with a text file that contains every file and its file-hash (crc32, md5, sha1, etc.). And the game e

Do it like AAA games that disallow modifications. They ship with a text file that contains every file and its file-hash (crc32, md5, sha1, etc.). And the game executable checks the hash of text file and then checks the hash of files listed in the text file.