I. Introduction
Smart grid is considered as one of the most important trends in next-generation power grids, which integrates the traditional power grid system with advanced information and communication technology [1]–[4]. A reliable, secure, flexible, and manageable information and communication network is the backbone of smart grids [5]. To support various network functions, many intelligent electronic devices, such as intelligent terminals and smart meters, have been deployed and used in smart grid systems [6]. Due to the installation of smart meters at user side, two-way communication (which can implement request and response) is established, and demand response is possible [7]. However, attackers can eavesdrop on the communication channel between user and control center, and identify the user’s electricity demand [8]. They can then track the user’s living habits or lifestyle, which are private information of the residents [9], [10]. Therefore, privacy protection is a very important issue during deployment of smart grids.