An ID-Based User Authentication Scheme for Cloud Computing In cloud computing environments, the user authentication scheme is an important security tool because it provides the authentication, authorization, and accounting for cloud users. Therefore, many user authentication schemes for cloud computing have been proposed in recent years. However, we find that most of the previous authentication schemes have some security problems. Besides, it cannot be implemented in cloud computing. To solve the above problems, we propose a new ID-based user authentication scheme for cloud computing in this paper. Compared with the related works, the proposed scheme has higher security levels and lower computation costs. In addition, it can be easily applied to cloud computing environments. Therefore, the proposed scheme is more efficient and practical than the related works.