156 http://inventwithpython.com/hacking

Email questions to the author: [email protected]

35. if myMode == 'encrypt':


36. translated = transpositionEncrypt.encryptMessage(myKey, content)


37. elif myMode == 'decrypt':


38. translated = transpositionDecrypt.decryptMessage(myKey, content)


39. totalTime = round(time.time() - startTime, 2)


40. print('%sion time: %s seconds' % (myMode.title(), totalTime))


41. 
    


42. 
    

    Write out the translated message to the output file.

    
    


43. outputFileObj = open(outputFilename, 'w')


44. outputFileObj.write(translated)


45. outputFileObj.close()


46. 
    


47. print('Done %sing %s (%s characters).' % (myMode, inputFilename,
    len(content)))


48. print('%sed file is %s.' % (myMode.title(), outputFilename))


49. 
    


50. 
    


51. 
    

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

    
    


52. 
    

    call the main() function.

    
    


53. if name == 'main':


54. main()

In the directory that frankenstein.txt and transpositionFileCipher.py files are in, there will be a
new file named frankenstein.encrypted.txt that contains the content of frankenstein.txt in
encrypted form. If you double-click the file to open it, it should look something like this:

PtFiyedleo a arnvmt eneeGLchongnes Mmuyedlsu0#uiSHTGA r sy,n t ys
s nuaoGeL
sc7s,
(the rest has been cut out for brevity)

To decrypt, make the following changes to the source code (written in bold) and run the
transposition cipher program again:

transpositionFileCipher.py

7. inputFilename = 'frankenstein.encrypted.txt'


8. 
   

   BE CAREFUL! If a file with the outputFilename name already exists,

   
   


9. 
   

   this program will overwrite that file.

   
   


10. outputFilename = 'frankenstein.decrypted.txt'


11. myKey = 10


12. myMode = 'decrypt' # set to 'encrypt' or 'decrypt'

This time when you run the program a new file will appear in the folder named
frankenstein.decrypted.txt that is identical to the original frankenstein.txt file.