Bdtyktl

so I have been trying to build an AES encryption program based off of the github pycrypto guide link to github however when I go to decode an error shows up:

Traceback (most recent call last):

File "/home/pi/Desktop/aes/newAES.py", line 24, in <module>

    print(decrypt(key,msg,iv))

File "/home/pi/Desktop/aes/newAES.py", line 13, in decrypt

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

File "/usr/lib/python3/dist-packages/Crypto/Cipher/AES.py", line 94, in new

    return AESCipher(key, *args, **kwargs)

File "/usr/lib/python3/dist-packages/Crypto/Cipher/AES.py", line 59, in __init__

blockalgo.BlockAlgo.__init__(self, _AES, key, *args, **kwargs)

File "/usr/lib/python3/dist-packages/Crypto/Cipher/blockalgo.py", line 141, in __init__

    self._cipher = factory.new(key, *args, **kwargs)

ValueError: IV must be 16 bytes long

my code is:

from Crypto.Cipher import AES

from Crypto.Random import get_random_bytes

def encrypt(key,msg):

    if key == 0:

        key=get_random_bytes(16)

        print("key: "+key)

    iv = get_random_bytes(16)

    print('iv: '+str(iv))

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

    ciphertext= cipher.decrypt(msg)

    return("your encrypted message: "+str(ciphertext))

def decrypt(key,ciphertext,iv):

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

    msg = cipher.decrypt(ciphertext)

ed = input('(e)ncrypt or (d)ecrypt: ')

if ed=='e':

    key = input('16 digit key: ')

    msg = input('message: ')

    print(encrypt(key,msg))

elif ed =='d':

    key = input('16 digit key: ')

    iv = bytes(input('iv: '),'utf-8')

    msg = bytes(input('encrypted message:'),'utf-8')

    print(decrypt(key,msg,iv))

I would appreciate any help offered on solving this issue, hopefully it isn't some stupid error

The problem with iv is that it consists of random bytes, but it is being read into your program as a string. Calling bytes on that string does not do what you expect.

>>> iv = b'xbax0eyO8x17xcfx97=xf2&l34#('

>>> siv = str(iv)

>>> siv

"b'\xba\x0eyO8\x17\xcf\x97=\xf2&l34#('"   # Note 'b' is part of the string

>>> biv = bytes(siv, 'utf-8')

>>> biv

b"b'\xba\x0eyO8\x17\xcf\x97=\xf2&l34#('"  # Now there are two 'b's!

You can resolve this by using ast.literal_eval:

>>> ast.literal_eval(siv)

b'xbax0eyO8x17xcfx97=xf2&l34#('

Here's a working version of your code - I removed the need to copy/paste iv, but the same observations about inputting bytes applies to the ciphertext.

import ast



from Crypto.Cipher import AES

from Crypto.Random import get_random_bytes





def encrypt(key, msg):

    iv = get_random_bytes(16)

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

    ciphertext = cipher.encrypt(msg)    # Use the right method here

    return iv + ciphertext





def decrypt(key, ciphertext):

    iv = ciphertext[:16]

    ciphertext = ciphertext[16:]

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

    msg = cipher.decrypt(ciphertext)

    return msg.decode("utf-8")





if __name__ == "__main__":

    ed = input("(e)ncrypt or (d)ecrypt: ")

    if ed == "e":

        key = input("16 digit key: ")

        msg = input("message: ")

        print("Encrypted message: ", encrypt(key, msg))

    elif ed == "d":

        key = input("16 digit key: ")

        smsg = input("encrypted message: ")

        msg = ast.literal_eval(smsg)

        print("Decrypted message: ", decrypt(key, msg))

The code in action:

(e)ncrypt or (d)ecrypt: e

16 digit key: abcdabcdabcdabcd

message: Spam, spam, spam

Encrypted message:  b'xa4?xa9RI>x1fxb5*xb2,NWNx0cxfd"yB|x1fx82x96xd5xb4xd4x1d&x8bMxdbx07'



(e)ncrypt or (d)ecrypt: d

16 digit key: abcdabcdabcdabcd

encrypted message: b'xa4?xa9RI>x1fxb5*xb2,NWNx0cxfd"yB|x1fx82x96xd5xb4xd4x1d&x8bMxdbx07'

Decrypted message:  Spam, spam, spam