Abstract: Cloud computing enables on-demand access to shared resources. It lets to use files and applications over the internet. This technology uses both the internet and the central servers to maintain data and resources. Many organizations uses cloud computing services to outsource their data into cloud environment for location independent resource pooling, elasticity and usage-based pricing. Since more enterprises store their private data on the cloud storage, privacy and security become major concern. One of the most challenging problem in Cloud computing is about the security of the outsourced data which is mainly handled by untrusted parties. This paper surveyed different types of techniques used to enhance the security of data stored in cloud environment and compare those techniques.