transpositionHacher

对于换位加密算法，我们知道，破译密文最重要的是搞到正确的key

---

所以我们重点关注key的取值

key的所有取值是   1 到 len(message) 

　　为什么不是0到 len(message)呢？

　　第一是因为默认密文是加密后的，第二如果key = 0, 那么在执行计算多少个格子时使用了

    numOfColumns = math.ceil(len(message) / key)

　　结果就是会出现除以0错误！

    。。。。。。

  File "d:PiaYiejczhang密码学py密码学编程教学代码	ranspositionHacker.py", line 11, in main
    hackedMessage = hackTransposition(myMessage)
  File "d:PiaYiejczhang密码学py密码学编程教学代码	ranspositionHacker.py", line 32, in hackTransposition
    decryptedText = transpositionDecrypt.decryptMessage(key, message)
  File "d:PiaYiejczhang密码学py密码学编程教学代码	ranspositionDecrypt.py", line 30, in decryptMessage
    numOfColumns = math.ceil(len(message) / key)
ZeroDivisionError: division by zero

破译算法：

# Transposition Cipher Hacker
# http://inventwithpython.com/hacking (BSD Licensed)

import pyperclip, detectEnglish, transpositionDecrypt

def main():
    # You might want to copy & paste this text from the source code at
    # http://invpy.com/transpositionHacker.py
    myMessage = """Cb b rssti aieih rooaopbrtnsceee er es no npfgcwu  plri ch nitaalr eiuengiteehb(e1  hilincegeoamn fubehgtarndcstudmd nM eu eacBoltaeteeoinebcdkyremdteghn.aa2r81a condari fmps" tad   l t oisn sit u1rnd stara nvhn fsedbh ee,n  e necrg6  8nmisv l nc muiftegiitm tutmg cm shSs9fcie ebintcaets h  aihda cctrhe ele 1O7 aaoem waoaatdahretnhechaopnooeapece9etfncdbgsoeb uuteitgna.rteoh add e,D7c1Etnpneehtn beete" evecoal lsfmcrl iu1cifgo ai. sl1rchdnheev sh meBd ies e9t)nh,htcnoecplrrh ,ide hmtlme. pheaLem,toeinfgn t e9yce da' eN eMp a ffn Fc1o ge eohg dere.eec s nfap yox hla yon. lnrnsreaBoa t,e eitsw il ulpbdofgBRe bwlmprraio po  droB wtinue r Pieno nc ayieeto'lulcih sfnc  ownaSserbereiaSm-eaiah, nnrttgcC  maciiritvledastinideI  nn rms iehn tsigaBmuoetcetias rn"""

    hackedMessage = hackTransposition(myMessage)

    if hackedMessage == None:
        print('Failed to hack encryption.')
    else:
        print('Copying hacked message to clipboard:')
        print(hackedMessage)
        pyperclip.copy(hackedMessage)


def hackTransposition(message):
    print('Hacking...')

    # Python programs can be stopped at any time by pressing Ctrl-C (on
    # Windows) or Ctrl-D (on Mac and Linux)
    print('(Press Ctrl-C or Ctrl-D to quit at any time.)')

    # brute-force by looping through every possible key
    for key in range(1, len(message)):
        print('Trying key #%s...' % (key))

        decryptedText = transpositionDecrypt.decryptMessage(key, message)

        if detectEnglish.isEnglish(decryptedText):
            # Check with user to see if the decrypted key has been found.
            print()
            print('Possible encryption hack as you check:')
            print('Key %s: %s' % (key, decryptedText[:100]))
            print()
            print('Enter D for done, or just press Enter to continue hacking:')
            response = input('> ')

            if response.strip().upper().startswith('D'):
                return decryptedText

    return None

if __name__ == '__main__':
    main()

看起来这么短，实际上有

import pyperclip, detectEnglish, transpositionDecrypt 

调用了大量的方法。

 

strip()方法

　　返回字符串首尾去掉空白（空格字符、制表符、换行符）后的版本

            # response.strip().upper().startswith('D')返回true or Flase  用来做好的用户体验

            # 灵活输入即可（而非严格的输入）