随着Internet带宽的不断增长，基于流媒体传输的视频应用得到了迅速的发展。然而，由于数字电视、视频邮件、可视电话等具体视频流应用在网络环境中很容易遭受人为的攻击，因此，视频流的网络安全成为当前亟待解决的重要研究课题之一。近年来，虽然出现了很多图像和视频的加密算法，然而很多算法在安全性或加密速度上存在缺陷。为此，结合其他算法的优点，提出了一种流密码与块密码相结合的加密算法。其中流密码用来产生伪随机序列，块密码用来置乱数据。由于Baker映射经改进后可以抵挡已知明文攻击，并且实现简单，而4维超混沌方程则不但可提高加密速度，还可增加密码的复杂度，因此可将Baker映射与4维混沌伪随机序列发生器相结合，前者用于块密码加密，后者用于流密码加密，其不但具有安全性高、速度快的特点，并且与视频压缩算法相独立．实现简单。实验结果表明．该算法可以进行实时视频传输和处理。

With the increase of Internet bandwidth, applications based on video stream have been developed rapidly. But the applications, such as digital video, videomail or videophone, are very vulnerable in network environment. Therefore video security has become an important research field. In recent years, a lot of image and video encryption algorithms and techniques have been used to solve the problem. However, most of them have drawbacks in security or speed. Combining with other algorithms’virtues, this article puts forward amethod that uses both stream ciphers to generate pseudo random numbers and block ciphers to do permutation. A 4 dimensional hyperchaotic function is chosen as stream ciphers, and Baker map as block ciphers. The improved Bakermap canwithstand known plain text attack in simple form. And the 4 dimensional hyperchaotic function can not only enhance encryption speed but also increase cipher complexity. This method, which can be simply realized by software, is independent of any kind of video compression algorithms, while providing high security for real time digital video with fast encryption speed.