Power grids are complex systems whose security and reliability depend on the collaboration among all the concerning entities, including peer operators, government authorities, etc. Data sharing in the manner of centralizing the data of peer operators in a common data center is highly desirable and even necessary to the collaboration and, in particular, applications such as global situational awareness in response to critical events. However, due to the concerns about privacy and security of data, the operators are reluctant to outsource their data. Hence, we propose , a mechanism that enables secure and efficient data sharing. The proposed scheme is demonstrated to achieve secure and unlinkable storage as well as fine-grained access control.