Cryptography With Python 简明教程

Decryption of Simple Substitution Cipher

在本章中，您可以了解替换密码的简单实现，该实现根据简单替换密码技术中使用的逻辑显示加密和解密消息。这可以认为是编码的另一种方法。

In this chapter, you can learn about simple implementation of substitution cipher which displays the encrypted and decrypted message as per the logic used in simple substitution cipher technique. This can be considered as an alternative approach of coding.

Code

您可以使用以下代码执行使用简单替换密码的解密 −

You can use the following code to perform decryption using simple substitution cipher −

import random
chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ' + \
   'abcdefghijklmnopqrstuvwxyz' + \
   '0123456789' + \
   ':.;,?!@#$%&()+=-*/_<> []{}`~^"\'\\'

def generate_key():
   """Generate an key for our cipher"""
   shuffled = sorted(chars, key=lambda k: random.random())
   return dict(zip(chars, shuffled))

def encrypt(key, plaintext):
   """Encrypt the string and return the ciphertext"""
   return ''.join(key[l] for l in plaintext)

def decrypt(key, ciphertext):
   """Decrypt the string and return the plaintext"""
   flipped = {v: k for k, v in key.items()}
   return ''.join(flipped[l] for l in ciphertext)

def show_result(plaintext):
   """Generate a resulting cipher with elements shown"""
   key = generate_key()
   encrypted = encrypt(key, plaintext)
   decrypted = decrypt(key, encrypted)

   print 'Key: %s' % key
	print 'Plaintext: %s' % plaintext
   print 'Encrypted: %s' % encrypted
   print 'Decrypted: %s' % decrypted
show_result('Hello World. This is demo of substitution cipher')

Output

上面的代码给出了如下所示的输出 −

The above code gives you the output as shown here −

implementation