This book focuses on three topics. The first topic is the effectiveness of the selective encryption approach. Selective encryption algorithms are very effective, thus have some weak points in their security. In this book, two successful security attacks against I-frame and DCT selective encryption algorithms are performed. Two algorithms are then proposed and evaluated accordingly. Our second topic is the coordination of multimedia security services. The conflict of data security algorithms and compression has introduced performance degradation and defective results. We invented an algorithm to completely eliminate compression from the fingerprinting loop to optimize performance. A second algorithm was invented for entertainment-level fast/effective encryption, particularly suitable for mobile devices, without noticeable compression overhead. The third topic is about how to detect and distinguish malicious attacks from allowable modifications in authentication. Using the hypothesis of decision border surface, an ideal solution of content authentication is proposed using a combination of generic authentications with classification techniques.