Controllable software licensing system for sub-licensing

The digital rights management is mainly about license management. Take software licensing as an example. A software license can be assigned to a user, a group of users, or an organization. To protect the copyright against software piracy, a software license is usually bound to the IP of the device or the identity of user. When a user wants to use a software product lawfully on multiple devices he owns, he has to purchase multiple licenses. We consider a scenario of software licensing where upon receiving a software license, the user can legally create a bounded number of licenses for his own devices. Our system is based on a novel chameleon function which is featured with -time trapdoors. By using this feature, we can construct a secure software licensing system, called “controllable -time software licensing system”. We formally prove that our software licenses are unforgeable, thanks to the collision resistance and indistinguishability feature of the proposed chameleon hash. We also provide the experimental results to demonstrate the computational efficiency of our system.