Abstract: A method and apparatus for authenticating gaming machine software is disclosed. In one embodiment the method and apparatus is used to authenticate the contents of a removable media. Use of a removable media provides means to store large amounts of software on a single media to install software, perform software updates, diagnose gaming machines, authenticate software, or configure gaming machines. An authentication file may contain a listing of each file on the removable media and an associated hash value calculated with a hash function. The hash values are calculated and stored in an authentication file and encryption of the one or more hash values may occur. A hash value re-calculation is performed on each file at a later time to determine the hash value at the time of use. The re-calculated hash values are compared to the decrypted hash values stored in the authentication file.