Teardown: 433MHz window sensor

We’ve had a look at at 433Mhz window sensor before, but are they all the same? Let’s check another one:


Ist this one different? It definitely is a bit larger. Why?


It runs on AAA batteries. That makes replacing the batteries easier and most likely cheaper than the special 12V battery we saw in the other sensor. If you want to use it as a security device, it is also nice to see that there is a switch connected to the case. If somebody tries to open the device, it will also send a message.


On the back there aren’t any surprises. Just the transmitter chip with a few external components and an LED.

The protocol used for the 433MHz RF transmissions is trivial. There is no encryption. This means it is extremely simple to record the signal from the sensor and play it back again. It depends on your use case, if this is a problem.

As the module tested before, this one also only sends a signal when the window opens, not when it closes. Therefore it can’t be used to detect if a window is open or close.

Accessing your Home assistant installation outside your house

Having a home automation solution that is only available inside your house might work for some people, but most people want to control their home also form the outside.

There are different options to achieve this in a secure way.


IC196810Using a VPN is usually the most secure solution. Even if there is a major security bug in your Home Assistant installation, attackers still can’t compromise your system as it isn’t publicly available on the internet. Many ISP’s today already provide a VPN service. You need to check with your ISP if it is available and how to configure it.

The disadvantage of a VPN is that you have to connect to the VPN first. This becomes an even bigger issue, if you use 3rd party applications (e.g. device trackers) that want to connect to your Home Assistant server. If the VPN isn’t connected, they will fail and some status informations might not be updated correctly.


Using a public HTTPS server is not the most secure solution, but still ok in general. Just note that you have to always check for security problems and update your Home Assistant installation regularly.

letsencryptFor HTTPS you will need certificates. A simple and free option today is Let’s encrypt. There is already a guide on the home assistant web site that shows how to use Home Assistant with Let’s Encrypt.

An additional security improvement can be implemented by using a web application firewall in front of the web server. While you can do this by yourself, it it quite complicated. Another option is using Cloudflare.  While you can’t use your own rules in the free version, it will still provide some basic security and protection against general attack patterns.

Comparison of both variants

Security Highest, as your system is protected even in case of security flaws in Home Assistant Ok, but you need to make sure that you regularly patch Home Assistant
Ease of setup Relatively easy if your ISP already offers it, otherwise complicated Medium, guides are available
Ease of use  Medium, you always have to connect the VPN first Very easy

Home Security with Raspberry Pi and a Webcam

Home security has never been easier. Though the terms “front end development” and “open source” may be daunting to some, Raspberry Pi hardware is a cost-effective and efficient solution that makes Home Automation a DIY commodity.

For $39.99, Raspberry Pi, is paired with a Mirco SD card (at least 2GB), USB Hub and a compatible webcam, to create a simple means of home security.

The Raspberry Pi is a self-powered motherboard, that either remotely or connected to a monitor and keyboard via its own USB ports. Having inserted a formatted SD card into the slot of the Motherboard, you can begin set up your Home Automation system. Your Webcam needs to be connected to a USB hub which is then connected to the motherboard in order to supply power to your camera.

First, Raspberry Pi needs to install an operating system to its motherboard. Whereas you can access your OS’s terminal directly, use of NOOBS’ Raspbian integrated OS, is the most convenient set up for beginners. Note that this option can be booted directly onto your Raspberry Pi, through a preloaded SD card.

Having inserted your SD card into your computer’s card reader, you will first need to format it to FAT-32. Following this, you can then download NOOBS and its integrated Raspbian software. Upon installing Raspbian on your computer, Windows Clients will need to download Win32 in order to burn this OS to an SD card, whereas Mac and Linux clients can do so by opening the Disk Utility and Terminal.

Once this is done, your SD card can be inserted into the Raspberry Pi.

For the convenience of simply controlling your electronics; such as a webcam, Raspberry Pi can then be controlled remotely from another device over a local network using a Secure Shell (SSH).

For remote access, you will need to download a free IP Scanner client and an SSH client such as Putty.  This will identify your Raspberry Pi from your OS. Taking note of your hardware’s IP address in the scan, you can remotely configure your Pi through the SSH client.

To install the camera connected to your USB hub, you will need to configure your Raspberry Pi’s terminal to enable it, and create a webcam server. Over a remote control server, the webcam can then be accessed from using the Pi’s IP address. There is also configuration available online to access your webcam stream from an internet browser. Alternatively, you can connect a camera module to Raspberry Pi’s CSI port, enabling your Raspberry Pi to become its own IP webcam.

Security in IOT

If you build your own home automation, security is something you should think of from the beginning. You don’t want somebody turning of your heating while you are away for skiing for a week. It is also not too much fun if somebody turns on the lights in your sleeping room during the night.
Joshua Corman explains the security risks in IOT applications (home automation is kind of an IOT application) and what to do to build secure systems.

Click on the image below to view his keynote from the 2016 IoT conference
Screenshot 2016-05-17 09.31.54

How secure is KNX?

Looking at modern home automation communication technologies (like Z-Wave or Zigbee), it seems that most of them have some security issues. These may or may not been fixed in the future. If these modern architectures already show a lot of problems, what about KNX? Let’s make it quick: from an computer security point of view, KNX is not just insecure, but the worst kind of protocol. All devices communicate on a shared medium, there is no encryption, no authentication, no authorisation. If you have access to the KNX bus, you can do everything.

Luckily, there is one good thing about KNX: You need access to the bus. If somebody has physical access to your bus, he can do crazy things. But this means, this person is already in your flat. Even without home automation, a person that has physical access to a light switch can turn it on and off. This means that for a residential installation, cabled KNX installations are perfectly fine, if they are running standalone. However, modern installations aren’t standalone. Nobody wants to install an home automation system anymore that is not somehow connected to a network.

Here are some tips how to make sure this system is still secure.

  1. Don’t simply connect your KNX network to your home LAN (that might be even allow guest WLAN access).
    KNX/IP interfaces are cool products and you will need one. However, be clear that these do not have any security built in. That means everybody that has access to your network can do everything on your home automation installation. This might not be the best idea. I would recommend some gateway that makes sure only authorised system can access your KNX bus.
  2. If you use any commercial product to connect your KNX bus to your LAN, (there are a lot of products available) make sure, the supplier provides regular updates and reacts on security incidents. If the last firmware you can find is 17 months old, the supplier most likely doesn’t do a good job. Most of these gateways are Linux based and you will need regular updates for it.
  3. If you implement some kind of gateway/firewall by yourself, make sure it is designed with security in mind and you also update it regularly.

Remark 1: The concept of physical security can be very critical in environments where multiple parties share a KNX installation. This can be a problem not only in office buildings, but also apartment complexes. If you live in an apartment with some kind of “smart” technology, have a look how it is implemented and who might be able to access it.

Remark 2: With ETS 5.5 the KNX association now supports some kind of encryption. I haven’t looked into it. Why? Because all old devices do not have any idea about it. It might become more popular in the future, but in today’s practical KNX installations, it is usually not supported by the devices that are already in place.

Z-Wave goodbye? Not yet

If you are interested in security, you might already know Steve Gibson’s podcast “Security now”. You might not agree with all of his opinions, but he collects quite a lot of information what’s happening in computer security. Make sure you understand what part of the podcast is advertisement and what is real information – as it is not always obvious.

At the latest episode, Steve has a look at an attack to Z-Wave that had been shown recently. As the podcast is always long, you should skip to 1:41 (minute 101).


Steve has some valid points against Z-Wave. Especially the fact that most of the standard isn’t publicly available means that there can be flaws in the design or the system that can’t be easily corrected. However, if you look at the presentation the podcast if referring to, you will see that the guys did not break the Z-Wave encryption. It just wasn’t available in the network they hacked into as it isn’t widely used today.

Does this mean Z-Wave is secure? Not really, but it also doesn’t mean that Z-Wave is insecure in general. We just don’t know yet how secure it is. Would I use it for a door lock? Most likely not. But it might be still a relatively inexpensive choice for some non-critical functionalities.


Is wireless the future?

Looking at new companies in the home automation industry it looks like many of them prefer some kind of radio frequency data transmission. This makes sense as customers don’t want to have additional cables in their home. But is this really the future of home automation? I’m not sure. Here are some arguments against wireless control:

  1. Reliability: with more and more devices communicating wireless, interoperability problems can become more and more problematic.
  2. Power supply: with some exceptions (e.g. EnOcean), even wireless devices need a power supply. This mean either cabling or batteries that need to be changed regularly
  3. Security: Wireless devices are easier to attack than wired devices (at least if these are not connected to a public network).

Especially the security aspect is important in my point of view. Many home automation devices will be used for 10-50 years. While it might be reasonable to buy a new music player every 5 years, you don’t want to change your wall switches every 10 years. The development of encryption algorithms has shown that no algorithm is secure forever. This means the software has to be updated from time to time. Newer encryption algorithms might even need more powerful hardware. Do you believe your supplier will provide software updates for the devices during the next 20 years?