Chapter 9 – The Transposition Cipher, Decrypting 127

32. plaintext = [''] * numOfColumns


33. 
    


34. 
    

    The col and row variables point to where in the grid the next

    
    


35. 
    

    character in the encrypted message will go.

    
    


36. col = 0


37. row = 0


38. 
    


39. for symbol in message:


40. plaintext[col] += symbol


41. col += 1 # point to next column


42. 
    


43. 
    

    If there are no more columns OR we're at a shaded box, go back to

    
    


44. 
    

    the first column and the next row.

    
    


45. if (col == numOfColumns) or (col == numOfColumns - 1 and row >=
    numOfRows - numOfShadedBoxes):


46. col = 0


47. row += 1


48. 
    


49. return ''.join(plaintext)


50. 
    


51. 
    


52. 
    

    If transpositionDecrypt.py is run (instead of imported as a module) call

    
    


53. 
    

    the main() function.

    
    


54. if name == 'main':


55. main()

When you run the above program, it produces this output:

Common sense is not so common.|

If you want to decrypt a different message, or use a different key, change the value assigned to
the myMessage and myKey variables on lines 5 and 6.

How the Program Works..........................................................................................................................................

transpositionDecrypt.py

1. 
   

   Transposition Cipher Decryption

   
   


2. 
   

   http://inventwithpython.com/hacking (BSD Licensed)

   
   


3. 
   


4. import math, pyperclip


5. 
   


6. def main():


7. myMessage = 'Cenoonommstmme oo snnio. s s c'


8. myKey = 8


9.