The smart grid, as the next generation of power grids, has attracted tremendous attention from both academia and the industrial community. Due to the two-way flows of energy and information, the smart grid enables utilities to sense and monitor the status in the power grid and respond to changes in power demand, supply, and cost in a close-loop way. The two-way communication, however, also raises new security and privacy challenges to power systems. In this chapter, we first describe a conceptual framework of the smart grid and propose some critical data security and privacy issues in the smart grid. Then, we review several popular data access control models and discuss their suitability to be adopted for ensuring data security and privacy in the smart grid. After that, we propose a privacy-preserving energy consumption data access control (ECDAC) scheme as a cryptographic implementation of attribute-based access control in the smart grid. Finally, we summarize this chapter and point out some open problems in the design of data access control schemes for the smart grid.