SDS2: Secure Data-Sharing Scheme for Crowd Owners in Public Cloud Service

In a public cloud, a data owner outsources encrypted data in order to protect its privacy. However, when sharing data with particular users, it is neither willing to share the decryption key nor reluctant to download and decrypt data. The former may reveal its identity and the latter can cause high computing and communication cost. In this paper, we proposed a half-decryption scheme (SDS2) for crowd owners to share privacy data with authorized users securely in a public cloud. Our scheme allows the owner to upload confidential data to a cloud, and deliver two half-decryption keys to a trusted authority and a user respectively according to our protocol. The trusted authority transfers the half-decryption key to the cloud after receiving a data sharing request. Then the user gets half-decrypted data from the cloud for further decryption. Experimental results show that computing and communication cost of our scheme is lower than other schemes with the increasing data and sharing requests.