License key based application security

I need a simple application locking mechanism with licensing key. The application should execute if it is bundled with the right license key. There will be 2 applications. One, that takes in a mac and generates a key file. Two, the main applications which reads this key file and exits if its invalid key file. Use case: 1. The user will provide the mac of the device to key generating app. This will take MAC and a private key to generate a key using SHA1/2/3 2. The key file is copied to the folder of the main application. 3. When the main application is run, it takes the MAC of the device/pc on which it is running, use the same private key to generate the key. This is compared with the key in the file provisioned by the user. If they match, the application will continue to run. Otherwise it will throw an error and exit. You may use any opensource library under liberal opensource license like BSD and not GPL.