A licensing system is disclosed for performing synchronous encryption with a client over an IP-compliant network. In disclosed embodiments, the system includes a licensing agent configured to pass a data structure unencrypted in an initial communication between the licensing agent/client pair and pass a first key to said client responsive to an initial communication. The licensing agent then receives the data structure from the client having designated fields encrypted according to the first key. The licensing agent then sends a second key to the client for use in subsequent communications.