scramble.py

def scramble_buffer(data: bytes, key: int):
    buf = bytearray()

    key_bytes = key.to_bytes(4, "little")
    step = (((((key >> 3 & 0x8000 | key & 0x4000) >> 6 | key & 0x80) >> 1 | key & 0x20) >> 1 | key & 8) >> 3)

    for b in data:
        if ((step != 0) and (len(buf) != 0)) and (len(buf) % step == 0):
            buf.append(buf[-1])

        buf.append(key_bytes[len(buf) & 3] ^ b)

    return buf


def unscramble_buffer(data: bytes, key: int):
    buf = bytearray()

    key_bytes = key.to_bytes(4, "little")
    step = (((((key >> 3 & 0x8000 | key & 0x4000) >> 6 | key & 0x80) >> 1 | key & 0x20) >> 1 | key & 8) >> 3)

    i = 0
    while i < len(data):
        if ((step != 0) and (len(buf) != 0)) and (i % step == 0):
            i += 1

        buf.append(key_bytes[i & 3] ^ data[i])

        i += 1

    return buf