As3Crypto (flex) with PyCrypto - how to make AES work?

Question

I have a client in Flex and a server in Python and i'm trying to make AES work between them but for some reason it doesn't work.

My server code:

import sys
from Crypto.Cipher import AES
from binascii import hexlify, unhexlify

BS = 16
pad = lambda s: s + (BS - len(s) % BS) * chr(BS - len(s) % BS)
unpad = lambda s : s[0:-ord(s[-1])]

def encrypt(str):
    cipher = AES.new(unhexlify('some 64 byte key here'), AES.MODE_CBC, '16 byte iv')
    hex_str = hexlify(cipher.encrypt(pad(str)))
    return hex_str

My client code:

static public function decrypt(txt:String) : String
{
    var k:String = "some 64 byte key here";
    var pad:IPad = new PKCS5();
    var mode:ICipher = Crypto.getCipher("aes-cbc", Hex.toArray(k), pad);
    pad.setBlockSize(mode.getBlockSize());

    var ivmode:IVMode = mode as IVMode;
    ivmode.IV = Hex.toArray(Hex.fromString("16 byte iv"));

    var data:ByteArray = Hex.toArray(Hex.toString(txt));
    mode.decrypt(data);

    return Hex.fromArray(data);
}

It seems like a simple case but I'm doing something wrong. What is it?

BTW: I get RangeError: Error #2006: The supplied index is out of bounds from mode.decrypt(data);

Answer 1

I finally managed to get it to work.

The client code should look like this:

static public function decrypt(txt:String) : String
{
    var k:String = "some 64 byte key here";
    var pad:IPad = new PKCS5();
    var mode:ICipher = Crypto.getCipher("aes-cbc", Hex.toArray(k), pad);
    pad.setBlockSize(mode.getBlockSize());

    var ivmode:IVMode = mode as IVMode;
    ivmode.IV = Hex.toArray(Hex.fromString("16 byte iv"));

    var data:ByteArray = Hex.toArray(txt);
    mode.decrypt(data);

    return Hex.toString(Hex.fromArray(data));
}