Many of the public cloud computing services have appeared for data storage in group applications. Two important problems that arise when sharing group data in public cloud are the privacy and security of group member’s data. Cloud service providers are separate administrative entities and users don’t have access to the cloud internal operational details. Because of the semi trust nature of cloud service provider, the traditional security technologies cannot be directly applied to the public cloud based group data sharing applications. The authors propose an efficient secure framework for public cloud based group application. This framework combines proxy signature scheme, incremental proxy re-encryption scheme and cipher text policy attribute based encryption together into a protocol.