Abstract: Bu and Wang ever put forward the way that using scalar signal to modulate the chaos carrier wave to enhance the security of the chaos secret communication，and defend the regression mapping attack of Preze and Cerdeira.Through transmission mode analysis of the Bu and Wang method，the authors discover the flaw of this method，i.e.，it can restore the parameter of the scalar signal from the modulation signal，and utilize the regression mapping to extract information from the demodulation chaos carrier signal.Therefore，in this paper the authors improve the Bu and Wang method，i.e.，increase a switching function that is bigger than 1 in the cryptograph.The numerical simulation of the generalized Rössler system indicates that the improved method can overcome the above flaw and enhance the communication security.

Key words: chaos carrier, regression mapping, secret communication, security

摘要： Bu和Wang曾提出利用标量信号调制混沌载波的方法，以提高混沌保密通信的安全性，并防御Preze和Cerdeira的回归映射攻击。通过对Bu和Wang方法的传输模式分析，发现了该方法的缺陷，即可从调制信号中恢复标量信号的参数，并利用回归映射从解调混沌载波信号中提取出消息。在此基础上改进了Bu和Wang的方法，即在密文中增加一个大于1的开关函数。通过对广义Rössler系统的数值模拟，表明改进方法既克服上述缺陷，又提高了通信的安全性。

关键词: 混沌载波, 回归映射, 保密通信, 安全性