serial_reverse.py

def get_serial_number(enc2):
    serial__number = [0 for n in range(0x400)]
    i = 0
    j = 0
    done_1 = False
    done_2 = False
    done_3 = False

    while j < len(enc2):
        if done_1 or done_2 or done_3:
            break
        for a in my_base64chars:
            if done_2:
                break
            if done_1:
                break
            for b in my_base64chars:
                if done_2:
                    done_1 = True
                    break
                if enc2[j] == ((my_base64chars.find(a) << 2) & 0xFF) | ((my_base64chars.find(b) >> 4) & 0xFF):
                    serial__number[i] = a
                    if j + 1 >= len(enc2):
                        serial__number[i + 1] = b
                        done_1 = True
                        break

                    for c in my_base64chars:
                        if enc2[j + 1] == ((my_base64chars.find(b) << 4) & 0xF0) | (
                                    (my_base64chars.find(c) >> 2) & 0xFF):
                            serial__number[i + 1] = b

                            if j + 2 >= len(enc2):
                                serial__number[i + 2] = c
                                done_2 = True
                                break

                            for d in my_base64chars:
                                if enc2[j + 2] == ((my_base64chars.find(c) << 6) & 0xC0) | (
                                            my_base64chars.find(d) & 0xFF):
                                    serial__number[i + 2] = c
                                    serial__number[i + 3] = d

        i += 4
        j += 3

    return bytearray(serial__number).strip(b'\x00').decode()