现有分数阶傅里叶变换（FRFT）由于旋转因子的单一性很少应用于视频实时加密，而当前单纯混沌加密算法的安全性又存在着诸多缺陷。为此，提出一种新的视频实时加密算法——混沌密钥调制DFRFT旋转因子。该算法将混沌加密与分数阶傅里叶变换进行了有机结合。首先将离散分数阶傅里叶变换（DFRFT）的旋转因子用混沌密钥进行调制，然后用调制后的旋转因子对视频数据进行分数阶傅里叶变换，最终完成了对视频数据的加密系统。该加密系统在技术上实现了视频数据在客户端的实时采集、实时加密；密文在网络上的实时传输、密文在接收端的接收、实时解密和播放。实验结果表明，加、解密效果很好，满足了实时性与安全性的要求。对实验结果的理论、安全性分析表明，该算法简单易行、安全性高。该算法的安全性优于单纯的混沌加密算法或单纯傅里叶视频加密算法，且满足了实时性要求。为解决实时性与安全性冲突问题提供了一条新的途径。

Because of the singleness of the rotation factor, fractional Fourier transform (FRFT) is rarely used in real-time video encryption. While at present,the simple chaotic encryption algorithms have many security problems. Consequently,a new real-time video encryption algorithm-chaotic key modulating discrete fractional Fourier transform (DFRFT) rotation factor is proposed. This algorithm combines chaotic encryption with DFRFT. First, we modulate the DFRFT rotation factor by a chaotic key. Second,we use the modulated rotation factor to carry on fractional Fourier transform,so as to complete the encryption operation for video data. The encryption system realizes real-time acquisition,real-time encryption and transmission, as well as real-time reception,real-time decryption and playing at the receiving terminal. The experimental results show that the system has a good effect in the encryption and decryption and can meet our real-time and security requirements. The theoretical analysis on the experiment results indicate that this algorithm is simple and practicable, with a high-level of security. The security of the algorithm is better than simple chaotic encryption algorithm or the simple FRFT encryption algorithm. We can draw a conclusion from results that this algorithm provides a novel mechanism for resolving the dispute between real-time and security.