What is Partial Encryption

In a wireless environment, multimedia transmission is often affected by the error rate; delaying; terminal’s power or bandwidth; and so forth, which brings difficulties to multimedia content protection. In the past decade, wireless multimedia protection technologies have been attracting more and more researchers. Among them, wireless multimedia encryption and watermarking are two typical topics. Wireless multimedia encryption protects multimedia content’s confidentiality in wireless networks, which emphasizes on improving the encryption efficiency and channel friendliness. Some means have been proposed, such as the format-independent encryption algorithms that are time efficient compared with traditional ciphers; the partial encryption algorithms that reduce the encrypted data volumes by leaving some information unchanged; the hardware-implemented algorithms that are more efficient than software based ones; the scalable encryption algorithms that are compliant with bandwidth changes; and the robust encryption algorithms that are compliant with error channels. Compared with wireless multimedia encryption, wireless multimedia watermarking is widely used in ownership protection, traitor tracing, content authentication, and so forth. To keep low cost, a mobile agent is used to partitioning some of the watermarking tasks. To counter transmission errors, some channel encoding methods are proposed to encode the watermark. To keep robust, some means are proposed to embed a watermark into media data of low bit rate. Based on both watermarking and encryption algorithms, some applications arise, such as secure multimedia sharing or secure multimedia distribution. In this chapter, the existing wireless multimedia encryption and watermarking algorithms are summarized according to the functionality and multimedia type; their performances are analyzed and compared; the related applications are presented; and some open issues are proposed.