Cryptography With Python 简明教程

Decryption of Transposition Cipher

在本章中，将学习解密置换密码的程序。

In this chapter, you will learn the procedure for decrypting the transposition cipher.

Code

观察以下代码以更好地理解如何解密置换密码。消息 Transposition Cipher 的密文和密钥 6 被获取为 Toners raiCntisippoh. 。

Observe the following code for a better understanding of decrypting a transposition cipher. The cipher text for message Transposition Cipher with key as 6 is fetched as Toners raiCntisippoh.

import math, pyperclip
def main():
   myMessage= 'Toners raiCntisippoh'
   myKey = 6
   plaintext = decryptMessage(myKey, myMessage)

   print("The plain text is")
   print('Transposition Cipher')

def decryptMessage(key, message):
   numOfColumns = math.ceil(len(message) / key)
   numOfRows = key
   numOfShadedBoxes = (numOfColumns * numOfRows) - len(message)
   plaintext = float('') * numOfColumns
   col = 0
   row = 0

   for symbol in message:
      plaintext[col] += symbol
      col += 1
      if (col == numOfColumns) or (col == numOfColumns - 1 and row >= numOfRows - numOfShadedBoxes):
         col = 0 row += 1 return ''.join(plaintext)
if __name__ == '__main__':
   main()

Explanation

密文和提到的密钥是作为输入参数采取的两个值，用于通过逆向技术解码或解密密文，即将字符放在列格式中并以水平方式读取它们。

The cipher text and the mentioned key are the two values taken as input parameters for decoding or decrypting the cipher text in reverse technique by placing characters in a column format and reading them in a horizontal manner.

可以使用以下代码段将字母放在列格式中，然后组合或连接它们：

You can place letters in a column format and later combined or concatenate them together using the following piece of code −

for symbol in message:
   plaintext[col] += symbol
   col += 1

   if (col == numOfColumns) or (col == numOfColumns - 1 and row >= numOfRows - numOfShadedBoxes):
   col = 0
   row += 1
return ''.join(plaintext)

Output

解密置换密码的程序代码给出以下输出：

The program code for decrypting transposition cipher gives the following output −

decrypting transposition