CODEWITHSUNDEEP
pythonaesvalueerrorpycryptodome
snow monster
snow monster

Reputation: 91

Python Incorrect AES key length despite passing the a 32 bytes bytearray

I have a specific AES key that I have to work with which is 10h,10h,10h,"A",10h,10h,10h,"AAA",10h,10h,10h,10h,10h,10h,10h,10h,10h,"A",10h,"A",10h,10h,"AA",10h,"A",10h,"A",10h,"A"

I have to use this key to encrypt a message. In python I covert it to "\x10,\x10,\x10,A,\x10,\x10,\x10,AAA,\x10,\x10,\x10,\x10,\x10,\x10,\x10,\x10,\x10,A,\x10,A,\x10,\x10,AA,\x10,A,\x10,A,\x10,A" but I get ValueError: Incorrect AES key length (60 bytes).

I tried encoding the key in a different way like key = bytearray("\x10,\x10,\x10,A,\x10,\x10,\x10,AAA,\x10,\x10,\x10,\x10,\x10,\x10,\x10,\x10,\x10,A,\x10,A,\x10,\x10,AA,\x10,A,\x10,A,\x10,A".encode('utf-8')) but I still get a same key length error.

What can I do in this case?

This is my code:

from Crypto.Cipher import AES
from Crypto.Random import get_random_bytes

msg = b"<input><type=\"update\"/></input>"
key = bytearray("\x10,\x10,\x10,A,\x10,\x10,\x10,AAA,\x10,\x10,\x10,\x10,\x10,\x10,\x10,\x10,\x10,A,\x10,A,\x10,\x10,AA,\x10,A,\x10,A,\x10,A".encode('utf-8'))

print(key)

cipher = AES.new(key, AES.MODE_GCM)
encrypted_msg = cipher.encrypt(msg)
print(encrypted_msg)

Upvotes: 0

Views: 761

Answers (1)

Nice Zombies
Nice Zombies

Reputation: 1107

How about using bytes instead?

#pip install pycryptodome
from Crypto.Cipher import AES
from Crypto.Random import get_random_bytes

msg = b"<input><type=\"update\"/></input>"
key = bytearray(b"\x10\x10\x10A\x10\x10\x10AAA\x10\x10\x10\x10\x10\x10\x10\x10\x10A\x10A\x10\x10AA\x10A\x10A\x10A")

print(key)

cipher = AES.new(key, AES.MODE_GCM)
encrypted_msg = cipher.encrypt(msg)
print(encrypted_msg)

This seems to be working. Please note that you can also use bytes.fromhex, which is more readable

#pip install pycryptodome
from Crypto.Cipher import AES

msg = b"<input><type=\"update\"/></input>" 
key = bytearray(bytes.fromhex("1010104110101041414110101010101010101041104110104141104110411041"))

print(key)

cipher = AES.new(key, AES.MODE_GCM)
encrypted_msg = cipher.encrypt(msg)
print(encrypted_msg)

Now, the good question: why does this happen? Well, utf-8 encodes the non ascii characters differently, pseudocode:

 '\x80    \x81    \x82    \x83    \x84    \x85    \x86    \x87    \x88    \x89    \x8a    \x8b    \x8c    \x8d    \x8e    \x8f    \x90    \x91    \x92    \x93    \x94    \x95    \x96    \x97    \x98    \x99    \x9a    \x9b    \x9c    \x9d    \x9e    \x9f    \xa0    \xa1    \xa2    \xa3    \xa4    \xa5    \xa6    \xa7    \xa8    \xa9    \xaa    \xab    \xac    \xad    \xae    \xaf    \xb0    \xb1    \xb2    \xb3    \xb4    \xb5    \xb6    \xb7    \xb8    \xb9    \xba    \xbb    \xbc    \xbd    \xbe    \xbf    '.encode()
b'\xc2\x80\xc2\x81\xc2\x82\xc2\x83\xc2\x84\xc2\x85\xc2\x86\xc2\x87\xc2\x88\xc2\x89\xc2\x8a\xc2\x8b\xc2\x8c\xc2\x8d\xc2\x8e\xc2\x8f\xc2\x90\xc2\x91\xc2\x92\xc2\x93\xc2\x94\xc2\x95\xc2\x96\xc2\x97\xc2\x98\xc2\x99\xc2\x9a\xc2\x9b\xc2\x9c\xc2\x9d\xc2\x9e\xc2\x9f\xc2\xa0\xc2\xa1\xc2\xa2\xc2\xa3\xc2\xa4\xc2\xa5\xc2\xa6\xc2\xa7\xc2\xa8\xc2\xa9\xc2\xaa\xc2\xab\xc2\xac\xc2\xad\xc2\xae\xc2\xaf\xc2\xb0\xc2\xb1\xc2\xb2\xc2\xb3\xc2\xb4\xc2\xb5\xc2\xb6\xc2\xb7\xc2\xb8\xc2\xb9\xc2\xba\xc2\xbb\xc2\xbc\xc2\xbd\xc2\xbe\xc2\xbf'

Upvotes: 2

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