Trusted software copyright protection is one of the most important issues in digital rights management. However, most of the current solutions could not meet the demand of End User License Agreement (EULA) in security and efficiency. In this paper, a new and secure authentication protocol for trusted copyright protection based on dynamic license is proposed to solve the above problem. A third part Certificate Authority (CA) is adopted for an atomic authorization and a forced revocation of software license dynamically according to the software and hardware identity and their usage status. Thus under the control of the dynamic license, the copyright is protected safely and the software entity can be transferred freely without copyright damage and resource leakage. Considering the integrity and security of the dynamic license, symmetric and public key cryptography algorithms are used for data encryption and digital signature respectively, while random verification of coding signature is adopted to resist possible attack and runtime crack. Analysis manifests that the proposed protocol is feasible and secure with a high integrity. It can meet the demand of EULA and provide a new and reliable approach for software copyright management.