任何一种保密通信系统,都应在密码分析者具有加密体制的全部知识和一段相当长的密信码以及适当长的相应的信码条件(即保密通信体制处于最恶劣条件)下,仍具有一定的保密性能。为此,可在信码加密之前,对信码进行予处理,再用密码加密。这种予处理可以“展平”信码的统计特性,减少或者消除信码的多余度。本文只讨论这种予处理方法。 Any kind of secure communication system should still have the knowledge that the cryptanalyst has all the knowledge of the cryptographic system and a fairly long secret code and the appropriate length of the corresponding code conditions (ie, the worst-case confidential communication system) A certain degree of confidentiality. For this purpose, the code can be pre-encrypted and then encrypted with the code before the code is encrypted. This preprocessing can “flatten” the statistics of the code, reducing or eliminating the redundancy of the code. This article discusses only this pre-treatment method.