Security, Privacy and Trust in Cloud Computing: A Comparative Study

``Use the computer without a computer,{''} this is the dream of all managers who believe in ``Cloud Computing{''}. The Cloud has become a dream and an obsession for all fans of the computer because of the many benefits this service offers: availability of services and data is ensured, cost is relative to consumption, ease of deployment, technical infrastructure is adaptable to the volume of business activity, its convenience to the common business applications (CRM, HR, BI, ERP, mail, etc.), the fact that this service provides a business function and not the technical components requiring computer skills. Besides these advantages, there are serious risks related to the use of Cloud computing, such as: temporary or permanent loss of data, security of data, lack of traceability and accountability. These risks are the main challenges faced while adopting a Cloud computing architecture. In this paper, we studied the literature focusing on three major notions on collaborative systems in Cloud computing: Security, privacy and trust. That's why we will try to bring out the main requirements regarding these three concepts from both points of view (user's and provider's), before presenting some related approaches which treat these three concepts.