古典多表密码体系的改进

The Improvement of The Classical Polyalphabetic Substitution

本文介绍了古典多表密码体系及其分析方法,根据该体系的弱点提出了改进的方法,并用同一实例对改进前、后体系进行了对比分析。分析结果表明,采用改进后的多表密码体系,密文周期是原来的26倍(当明文是英语字母时),可用于字数较少的报文加密,尤其适用于随机字母序列(如密码、口令等)的加密。

The classical polyalphabetic substitution and its cryptanalysis have been introduced by the article. A improvement has been put forward after the analysis of the polyalphabetic substitution. And a comparative test has been made using a same plain text. The result shows that the periodicity of the cryptograph is 26 multiple (when the plain text is written by English) of the classical. So it is useful to encrypt a short telegram, specially in random series of letters(such as cipher or password).