Abstract: Cloud storage is a model of data storage, whose demand is greatly increasing. The data sharing is one of the concerning functionality in today’s world of information as it involves security, efficiency and flexibility as their important aspects. Various schemes and methodologies are implemented to make data sharing more effective. With the introduction of encryption and decryption schemes, the storing, sharing and securing of data became rampant. The storing of these ciphertexts and the decryption keys is one of the major issues. There is a need for a mechanism which can minimize the cost of storing these ciphertexts and keys in a secured way. In this paper, we explore the various encryption schemes which were proposed to solve this problem. In this era of information, where there is presence of rich data, the true value lies in sharing, securing and storing them. Protecting users’s data privacy is one of the critical goal of cloud storage. The present research efforts concentrates more on aggregation of these keys into a single aggregate key which will in turn reduce the burden on the network overhead.

Keywords: Cloud storage, data sharing, ciphertexts, encryption schemes