Cloud computing is an emerging technology that uses the concepts of storage, virtualization, connectivity and processing power to store resources and share them between computers and other devices via the internet and central remote servers. Ensuring the security of cloud computing is the challenging issue in the cloud environments. According to the importance of security in this technology, this book offers a real-time method for maintaining the client-based security in cloud computing communications to ensure the establishment of a secure and trust-based access. The proposed model will contain an eligible algorithm to solve the identified problems. For achieving to this purpose, a client-based encryption system should develop to share an encrypted key between the intended recipients for transparently and securely sharing. Moreover, this client-base system should contain user authentication evaluation for validating user legal identities and acquiring their access control privileges for the resources according to the role information. By developing this model, the author can investigate the effects of this system on trustable and reliable cloud computing communications.