There is provided a method of permitting one or more features on a computer program. The computer program executing on a hardware with a hardware identifier. The method comprises, at the authentication server, receiving an authentication key indicating authorised features of the computer program, generating a server key based on the hardware identifier and a feature list, and comparing the authentication key with the server key. The method further comprises, at the authentication client, receiving a feature request comprising one or more features to be permitted on the computer program, generating a feature verification message based on the one or more features, and transmitting the feature verification message to the authentication server. The method further comprises, at the authentication server, receiving the feature verification message, verifying that the one or more features are within the feature list, generating a response key if the one more or more features are within the feature list and the authentication key matches the server key, and transmitting the response key to the authentication client. The method further comprises, at the authentication client, receiving the response key, and permitting the one or more features on the computer program.