Digital watermarking is a technology being developed to ensure and facilitate data authentication, security and copyright protection of digital media. The authors have studied about watermarking technique for authentication of cloud users. They propose to use both secure sharing and watermarking schemes to protect users' data in the media cloud. The secure sharing scheme allows users to upload multiple data pieces to different clouds, making it impossible to derive the whole information from any one cloud. In addition, the proposed scalable watermarking algorithm can be used for authentications between personal mobile users and the media cloud.