A Review Paper on Secure authentication and data sharing in cloud storage using key aggregate cryptosystem

Cryptography is the study of mathematical techniques related to aspects of information security such as confidentiality, data integrity, entity authentication and data again authentication. We describe new public-key cryptosystems that produce constant-size cipher texts such that efficient delegation of decryption rights for any set of cipher texts is possible. Cryptosystem or cryptographic system is any sort of methodology for encoding and accessing that information. In this technique the master key holder can release a constant-size aggregate key for flexible choices of cipher text set in cloud storage, but the other encrypted files outside the set remain confidential. This compact aggregate key can be conveniently sent to others or be stored in a smart card with very limited secure storage. We provide formal security analysis of our schemes in the standard model. We also describe other application of our schemes. In particular, one can aggregate any set of secret keys and make them compact as a single key but encompassing the power of all the keys being aggregated.