Reviewing the PandwaRF: CC1111 Based Transceiver for RF Security Analysis

The PandwaRF

The PandwaRF (formerly known as GollumRF) is an RF analysis transceiver tool that can be very useful for investigating ISM band devices that communicate with digitally modulated RF signals. It can be used for applications such as performing replay attacks, brute force attacks, and other analysis. The RX/TX frequency range of the device is from 300 – 928 MHz, with a transmit power of up to +10 dBm.

The PandwaRF is based on the CC1111 chip which is the same chip used in devices like the Yard Stick One from Great Scott Gadgets (creators of the HackRF). Compared to the YS1 the PandwaRF is essentially the same, but designed to be much more portable, with a built in battery and an Android app that you connect to via Bluetooth. This makes it very useful for taking out in the field as no laptop is required to use it, just a phone or tablet. The PandwaRF can be used just like a YardstickOne when plugged into a PC however.

We should also clarify that CC1111 based devices like the PandwaRF and YS1 are not classed as SDRs. Rather they are RF transceiver chips that can demodulate, decode and transmit a fixed set of digital modulation schemes, such as OOK/ASK, 2-FSK, 4-FSK, GFSK, and MSK. While these devices are not able to receive or transmit any arbitrary signal like an SDR, they make reverse engineering, analysis, replay attacks, brute force attacks etc much simpler for common modulation schemes compared to using an SDR for the same purpose.

Early on in the year PandwaRF sent us a sample of their device for review. Unfortunately during that time their Android software was extremely buggy and we were simply unable to use the device properly. Others reported similar troubles on forums and blog comments. However fast forward to today and it now seems that the Android software is stable and functioning properly.

Replay Attack

PandwaRF Spectrum Analyzer Tool
PandwaRF Spectrum Analyzer Tool

We first tested the PandwaRF on a simple task which was a replay attack. The goal was to record the signal of a cheap wireless RF alarm, and see if we could replay it back. The wireless alarm is controlled with a keyfob.

First we used the Spectrum Analyzer tool in the PandwaRF app to try and get the frequency of the keyfob. The Spectrum Analyzer tool allows you to see about 1.2 MHz of bandwidth. We assumed the signal would be around 433 MHz. After pressing the button a few times the peak showed up at about 433.9 MHz on the spectrum analyzer. The refresh rate of the spectrum analyzer is quite low, so if the signal is not continuous it’s possible to miss the signal, which is we why we had to try several presses before the signal showed. A standard SDR like an RTL-SDR might be better for this initial frequency searching. We confirmed the frequency to be at 433.893 MHz on an RTL-SDR blog V3.

PandwaRF RX/TX Replay Attack Screen
PandwaRF RX/TX Replay Attack Screen

Next we switched to the RX/TX tool. Here you can enter the frequency of interest and set the expected modulation. We know that this device is ASK/OOK modulated, so we chose this setting. You also need to set the data rate. If you don’t know this value then the app has a data rate measuring tool. So we just pressed on the Measure button, and then pressed a button on the remote until it converged to a data rate of 5,121.

Next you need to set the ‘desired payload’. This is how many bytes long the packet is and determines how long the capture is. As we were unsure we simply set it to 250 bytes to ensure that a longer capture was taken. The PandwaRF will keep on receiving until it receives the desired payload of 250 bytes or is stopped manually. Setting it longer allows us to capture a longer signal, and ensure that the replayed signal is received. For this alarm device it is okay if the same signal is played multiple times in a short time frame.

The final setting is the RX Frame length. This determines how many bytes will be captured before transferring the data to Android. So for example, if you set the desired payload to 100 Bytes, and the RX Frame length to 52 bytes, then in total you will capture 104 Bytes of data. The PandwaRF can only transfer in 14, 33, 52, 71 or 90 bytes, so select one that is closest to a multiple of your desired payload.

Finally we pressed on ‘Sniff’ and pressed the ‘bell’ button on the remote. The PandwaRF detected the signal and recorded the data. Now pressing Xmit replays the signal successfully causing the alarm bell to sound.

Replayed and Original Signal received with an RTL-SDR
Replayed and Original Signal received with an RTL-SDR

Brute Force Attack

Brute force settings
Brute force settings

The PandwaRF can also be used as a brute forcing tool. With cheap alarms the alarm code is relatively short, so can be brute forced in a matter of minutes. The PandwaRF already had a preset mode for our cheap Forecum door alarm, so we simply selected this mode and started the brute force. It gave an estimated brute force time of 28 minutes, which is the time it takes to run through every possible alarm code.

More advanced brute force settings
More advanced brute force settings

The PandwaRF app currently supports the Idk and PT2262 chipsets, as well as some models of DIO, Extel and Forecum house alarms. If the device that you want to brute force is not yet in their database, then you’ll probably need to do some analysis first on the PC with an SDR. Software like Universal Radio Hacker and DSpectrumGUI are good tools for this. Once you know the structure of the data, then you can program PandwaRF to perform the brute force attack.

Note that their newer ‘PandwaRF Rogue’ product is supposed to be significantly faster at brute forcing. For example the Android software gives us a estimated duration of 28 minutes with the standard PandwaRF, and only 3 minutes with the Rogue.

The Rogue is also able to brute force 32 bit codewords with zero delay in between transmissions. The standard PandwaRF has a minimum delay of 100 ms which can really slow things down. It also allows for function mask bit skipping, enable more brute force patterns and can split the brute force attempt into several steps. Also as we’ve seen from their videos the Rogue has more pre-set commercial devices built into its app.

So if brute forcing is your main use for the PandwaRF then it seems to make sense to get the Rogue. Unfortunately the Rogue is significantly more costly, coming in at 990 euros, vs 145 euros for the standard PandwaRF. Of course you could still use the standard PandwaRF on a PC with tools like rfcat to perform a faster brute force attack as well, just like you would with a YardstickOne.

PandwaRF Brute Force attack as seen by an RTL-SDR
PandwaRF Brute Force attack as seen by an RTL-SDR

Javascripting

Javascript in PandwaRF

If you need more powerful analysis or TX capabilities, then the PandwaRF can be controlled in Javascript code. For example, you might have already reverse engineered a device, and simply require the PandwaRF to transmit the correct code to replace a remote control. You could also create a jammer with this.

The code runs on the Android device and not on the PandwaRF, so each RF command generates a bluetooth transfer which can be quite slow. They write this is why they have created a specific brute force implementation in the app, so that they can run their native brute force code on the PandwaRF itself, which is must faster than transferring the RF command for every brute force step.

Conclusion

Overall the PandwaRF is a very handy tool for doing replay and brute force attacks while in the field. It can also be converted back into a PC based CC1111 device, like a Yardstick One simply by plugging it into a computer with a USB cable so you’re not missing out on that functionality either.

Compared to the Yardstick One the cost is a bit more, with the Yardstick One costing $99 USD at most outlets, and the PandwaRF costing 145 Euros (~$173 USD). So it is probably only really worth it if you are doing field testing.

That said, now that the PandwaRF software seems stable it is an excellent tool for investigating wireless devices in a simpler way compared to with an SDR. An SDR is still much more powerful, but tools like this simplify the process significantly. The best set of tools for reverse engineering would be a SDR combined with a device like this.

In the future it looks like they plan to implement new features such as De Bruijn (OpenSesame) attack’s and rolling code attacks and we look forward to testing those out.

If you want more information about the PandwaRF you can visit their site, or check out their Wiki, or have a look at the demo videos on their YouTube page.

Disclaimer: The PandwaRF was provided to us for free in exchange for an honest review.

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