user65165 - 7 months ago 36

Python Question

I have written the following classes to be able to test different encryption schemes. However, I'm having trouble instantiating objects from the different encryption scheme. Could someone point out to something that doesn't make sense that I'm not catching atm? I'm not sure why it doesn't work. It gives a

`TypeError: encrypt() takes exactly 3 arguments (2 given)`

`class AXU:`

def __init__(self, sec_param):

self.sec_param = sec_param

def getHash(self):

# sample a, b and return hash function

a = random.randrange(self.sec_param)

b = random.randrange(self.sec_param)

return lambda x : a*x+b % sec_param

class BC(object):

def __init__(self, sec_param):

# generate a key

self.sec_param = sec_param

def encrypt(self, message, key):

#encrypt with AES?

cipher = AES.new(key, MODE_CFB, sec_param)

msg = iv + cipher.encrypt(message)

return msg

class tBC(object):

def __init__(self, sec_param):

self.sec_param = sec_param

def encrypt(self, tweak, message):

#pass

return AES.new(message, tweak)

class Trivial(tBC):

def __init__(self):

self.bcs = {}

def encrypt(self, tweak, message):

if tweak not in self.bcs.keys():

bc = BC()

self.bcs[tweak] = bc

return self.bcs[tweak].encrypt(message)

class Our(tBC):

def __init__(self, sec_param):

self.bc1 = BC(sec_param)

self.bc2 = BC(sec_param)

self.bc3 = BC(sec_param)

self.bc4 = BC(sec_param)

# encryption over GF field

def encrypt(self, tweak, message):

return self.bc1.encrypt(self.bc2.encrypt(tweak) * self.bc3.encrypt(message) + self.bc4.encrypt(tweak))

edit: my bad sorry. forgot to add this

`message_instance = 'This is a message to the board of directors.'`

tweak = os.urandom(16) #16 bytes=128 bits

our_encr = Our(256)

our_encr.encrypt(message_instance, tweak)

Answer

You are passing in **one** argument to a bound method:

```
return self.bc1.encrypt(
self.bc2.encrypt(tweak) * self.bc3.encrypt(message) +
self.bc4.encrypt(tweak))
```

That's one argument to the `BC.encrypt()`

method each, and this method takes 2 beyond `self`

, `message`

and `key`

.

Either pass in a value for `key`

, or remove that argument from the `BC.encrypt()`

method definition (and get the key from some place else; perhaps from an instance attribute set in `__init__`

).