Trusted Cloud for Data Sharing.

Cloud computing is a general term for anything that involves delivering hosted services over the internet. These services are broadly divided into three categories: Infrastructure-as-a-Service (IaaS), Platform-as-a Service (PaaS) and Software-as-a-Service (SaaS). A cloud service has three distinct characteristics that differentiate it from traditional hosting. It is sold on demand, typically by the minute or the hour; it is elastic - a user can have as much or as little of a service as they want at any given time and the service is fully managed by the cloud service provider (the consumer needs nothing but a personal computer and Internet access).The advantage of cloud is cost savings. The prime disadvantage is security. Cloud computing is used by many software industries nowadays. Since the data placed in the cloud is accessible to everyone, security is not guaranteed. Cloud Computing provides the way to share distributed resources and services that belong to different organizations or sites. Since Cloud Computing share distributed resources via network in the open environment thus it makes security problems. All types of users who require the secure transmission or storage of data in any kind of media or network. By this new technology, users also start worrying about losing control of their own data. The data processed on clouds are often outsourced, leading to a number of issues related to accountability, including the handling of personally identifiable information. Such fears are becoming a significant barrier to the wide adoption of cloud services. To allay users’ concerns, it is essential to provide an effective mechanism for users to monitor the usage of their data in the cloud. For example, users need to be able to ensure that their data are handled according to the service level agreements made at the time they sign on for services in the cloud.