Python Forensics 简明教程

Python Forensics - Cracking an Encryption

在本章中，我们将了解如何在分析和证据期间破解提取的文本数据。

密码学中的纯文本是一些正常的可读文本，例如一条消息。另一方面，密文是由输入纯文本后提取的加密算法的输出。

我们将明文消息转换为密文消息的简单算法是 Caesar cipher ，这是 Julius Caesar 发明的，用于向他的敌人保密明文。此密码涉及将消息中的每个字母在字母表中向前移动三个位置。

以下是一个演示说明。

a → D

b → E

c → F

w → Z

x → A

y → B

z → C

Example

A message entered when you run a Python script gives all the possibilities of characters, which is used for pattern evidence.

The types of pattern evidences used are as follows −

  1. Tire Tracks and Marks

  2. Impressions

  3. Fingerprints

Every biometric data comprises of vector data, which we need to crack to gather full-proof evidence.

The following Python code shows how you can produce a cipher text from plain text −

import sys

def decrypt(k,cipher):
   plaintext = ''

   for each in cipher:
      p = (ord(each)-k) % 126

      if p < 32:
         p+=95
         plaintext += chr(p)
         print plaintext

def main(argv):
   if (len(sys.argv) != 1):
      sys.exit('Usage: cracking.py')
      cipher = raw_input('Enter message: ')

      for i in range(1,95,1):
         decrypt(i,cipher)

if __name__ == "__main__":
   main(sys.argv[1:])

Output

Now, check the output of this code. When we enter a simple text "Radhika", the program will produce the following cipher text.

Cracking Encryption Output