Cloud computing is a virtualized compute power and storage delivered via platform-agnostic infrastructures of abstracted hardware and software accessed over the Internet. Data sharing is an important functionality in cloud storage. Describe new public-key crypto systems which produce constant-size cipher texts such that efficient delegation of decryption rights for any set of cipher texts are possible. Show how to securely, efficiently, an flexibly share data with Decoy technology in secure cloud storage. Cipher texts are possible. The novelty is that one can aggregate any set of secret keys and make them as compact as a single key but encompassing the force of all the keys being aggregated. So provide formal security analysis of our schemes in the standard model and describe other application of our schemes. In other words, the secret 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. It Decoy technology provide security, Flexibility and confidentiality in data sharing.