Wireless networks are poised to enable a variety of existing and emerging video streaming applications. However, video streaming over wireless suffers from piracy and malicious attack. Also, it is well-known that video decompression on the handheld devices is constrained by the power and other computation resource. Therefore, video encryption should be designed to be lightweight and efficient. In this paper, we designed a new lightweight, efficient, scalable, format-compliant video encryption algorithm, which is based on the DCT (Discrete Cosine Transformations) coefficients scrambling. The simulation shows that the proposed video encryption algorithm consumes low computation resource while achieves high scalability and confidentiality, which is in compliance with the design goal of video streaming over wireless applications.