384 http://inventwithpython.com/hacking

Email questions to the author: [email protected]

19. p = rabinMiller.generateLargePrime(keySize)


20. print('Generating q prime...')


21. q = rabinMiller.generateLargePrime(keySize)


22. n = p * q


23. 
    


24. 
    

    Step 2: Create a number e that is relatively prime to (p-1)*(q-1).

    
    


25. print('Generating e that is relatively prime to (p-1)*(q-1)...')


26. while True:


27. 
    

    Keep trying random numbers for e until one is valid.

    
    


28. e = random.randrange(2 (keySize - 1), 2 (keySize))


29. if cryptomath.gcd(e, (p - 1) * (q - 1)) == 1:


30. break


31. 
    


32. 
    

    Step 3: Calculate d, the mod inverse of e.

    
    


33. print('Calculating d that is mod inverse of e...')


34. d = cryptomath.findModInverse(e, (p - 1) * (q - 1))


35. 
    


36. publicKey = (n, e)


37. privateKey = (n, d)


38. 
    


39. print('Public key:', publicKey)


40. print('Private key:', privateKey)


41. 
    


42. return (publicKey, privateKey)


43. 
    


44. 
    


45. def makeKeyFiles(name, keySize):


46. 
    

    Creates two files 'x_pubkey.txt' and 'x_privkey.txt' (where x is the

    
    


47. 
    

    value in name) with the the n,e and d,e integers written in them,

    
    


48. 
    

    delimited by a comma.

    
    


49. 
    


50. 
    

    Our safety check will prevent us from overwriting our old key files:

    
    


51. if os.path.exists('%s_pubkey.txt' % (name)) or
    os.path.exists('%s_privkey.txt' % (name)):


52. sys.exit('WARNING: The file %s_pubkey.txt or %s_privkey.txt already
    exists! Use a different name or delete these files and re-run this program.' %
    (name, name))


53. 
    


54. publicKey, privateKey = generateKey(keySize)


55. 
    


56. print()


57. print('The public key is a %s and a %s digit number.' %
    (len(str(publicKey[0])), len(str(publicKey[1]))))


58. print('Writing public key to file %s_pubkey.txt...' % (name))


59. fo = open('%s_pubkey.txt' % (name), 'w')


60. fo.write('%s,%s,%s' % (keySize, publicKey[0], publicKey[1]))