Described is a method and system for controlling usage of software on a computing device. An authorization key is generated as a function of a device string and a software string. The device string is a unique string stored in the device. The software string is a unique string stored in a software authorized for use on the device. The authorization key is encrypted using a private key and stored in the device. Upon a request to use software on the device, the authorization key is decrypted using a public key corresponding to the private key. A test key is generated as a function of the device string and a request software string. The request software string is a unique string stored in the software for which use has been requested. The authorization key is compared to the test key. When the test key matches the authorization key, usage of the software for which use has been requested on the device is permitted.