Smart Grid facilitates real-time communication network between the user and the grid company by smart terminals, which utilizes bidirectional data transmission and information control. In Smart Grid, the smart meters play important role by measuring the amount of electricity consumption and sending various information to the power generators and substations. The communication of such information raises privacy concerns from the users about their private information leakage. Therefore, Confidentiality and integrity of smart meter readings are important as altering such data can lead to incorrect billing and false energy usage approximations. In order to insure the security of communication in Smart Grid, we propose the use of ID-based signcryption scheme using bilinear pairing and time factor. It satisfies the requirements for secure communication. It is also efficient, which makes it suitable for low power, low storage sensors in home appliances devices.