Cloud computing is an innovation of existing technology which provides long-dreamed vision of computing as utility. The emergence of this novel technology in IT business has decoyed most of organizations in both private and public sector. Cloud services can be availed without capital investment as they are commoditized. Cloud users get services in pay per use fashion and enjoy many benefits of cloud including low cost and accessibility from anywhere in the world. However, users have security concerns as they outsource their valuable business data to cloud and treat the cloud as "Untrusted".