crypto_tools.py

from Cryptodome import Random
from Cryptodome.Cipher import AES
import base64
import hashlib


def pad(data):
    block_size = 16
    length = block_size - (len(data) % block_size)
    return data + (chr(length)*length).encode()


def unpad(data):
    return data[:-(data[-1] if type(data[-1]) == int else ord(data[-1]))]


def bytes_to_key(data, salt, output=48):
    assert len(salt) == 8, len(salt)
    data += salt
    key = hashlib.md5(data).digest()
    final_key = key
    while len(final_key) < output:
        key = hashlib.md5(key + data).digest()
        final_key += key
    return final_key[:output]


def encrypt(message, passphrase):
    salt = Random.new().read(8)
    key_iv = bytes_to_key(passphrase, salt, 32+16)
    key = key_iv[:32]
    iv = key_iv[32:]
    aes = AES.new(key, AES.MODE_CBC, iv)
    return base64.b64encode(b"Salted__" + salt + aes.encrypt(pad(message)))


def decrypt(encrypted, passphrase):
    encrypted = base64.b64decode(encrypted)
    assert encrypted[0:8] == b"Salted__"
    salt = encrypted[8:16]
    key_iv = bytes_to_key(passphrase, salt, 32+16)
    key = key_iv[:32]
    iv = key_iv[32:]
    aes = AES.new(key, AES.MODE_CBC, iv)
    return unpad(aes.decrypt(encrypted[16:]))


def hash(aes_key):
    h = hashlib.sha256(aes_key.encode()).digest()
    res = base64.b64encode(h).decode('utf8').replace(
        "/", "_").replace("+", "-").replace("=", "")
    return res