I receive a base64 encoded string. The first 16 bytes are the IV. I need to extract them before I decrypt with CryptoJS.

For the past few days, I’ve been trying to understand how this code fragment in JavaScript with the CryptoJS library works. I want to port it to Python. I’ve written an AES algorithm that replicates the JavaScript error, which occurs because AES accepts keys larger than 256 bits, but the number of rounds changes: for 256 bits / 32 + 6 = 14 rounds, for 512 bits / 32 + 6 = 22 rounds, and so on. I’ve also replicated the EvpKDF algorithm in Python using MD5.