进行字母频率攻击的单字母替代密码程序

The challenge is to display the top five probable plain texts which could be decrypted from the supplied monoalphabetic cypher utilizing the letter frequency attack from a string Str with size K representing the given monoalphabetic cypher.

Let us see what exactly is frequency attack.

频率分析的基础是确信特定的字母和字母组合在任何给定的书面语言部分中以不同的频率出现。此外，事实上，该语言的每个样本在字母分布上都有一个共同的模式。为了更清楚地说明，

英语字母表有26个字母，但并不是所有字母在书面英语中使用频率都相同。某些字母的使用频率是不同的。例如，如果你查看一本书或报纸上的字母，你会注意到字母E、T、A和O在英语单词中出现得非常频繁。然而，英语文本很少使用字母J、X、Q或Z。这个事实可以用来解密维吉尼亚密码的信息。术语"频率分析"就是指这种方法。

Each letter found in the plaintext is substituted with a different letter in a basic substitution cypher, and any given character in its plaintext is perpetually changed to an identical letter in the text of the cypher. A ciphertext message with several repetitions of the letter Y, for instance, would imply to the cryptanalyst that Y stands in for the letter a if every instance of the letter a are converted to the letter X.

示例示例1

Let us take string T,

按照英文字母在英语字母表中的降序连接形成的字符串。

String T=ETAOINSHRDLCUMWFGYPBVKJXQZ” Given string Str = "SGHR HR SGD BNCD"; 登录后复制