White Paper- WiFi Testing in Silence€¦ · White Paper- WiFi Testing in Silence Flexible EM...

White Paper- WiFi Testing in Silence Flexible EM Shielding Solution for Isolating WAP’s of Interest EDEC Digital Forensics Nick Adelchanow January 15, 2015

EDEC Digital Forensics | 421 N Milpas St, Santa Barbara CA, 93103 | www.edecdf.com

Introduction

While the widespread adoption of WiFi has countless advantages compared to wired networks, it also brings new challenges for developers and salespeople. In addition to irritating cross-talk between multiple networks in a testing environment, developers of WiFi technology are often in close proximity to relatively high-power devices, subjecting the developers to high levels of potentially harmful EM energy. Salespeople, on the other hand, may struggle to connect to a proper network during a demo due to the numerous WiFi source/s typically found in a mock environment. Until now the only solutions to these problems have come in the form of expensive, heavy EM shielding boxes or leaky/hard-to-work-with anti-static bags. Neither solution is ideal -- too large, too expensive, or just ineffective. EDEC Digital Forensics has developed an innovative solution to this problem - a durable, cost effective, sized-to-application bag with the EM absorption of a black hole! Introducing, the Black Hole Data Test Bag.

Black Hole Test Bag outside showing Black Hole Test Bag inside showing USB connector and TNC connector USB filter block and TNC with antenna connected


Background

The introduction of WiFi is now the cornerstone of mobile consumer products and the ability to make wireless devices that are increasingly smaller, more powerful, and cheaper is driving the adoption of mobile devices in almost every aspect of our lives. From tablets to wearables to the IoT (Internet of Things), there is no end in sight to the explosive, exponential growth in wireless connectivity. Most current operating systems on wireless devices allow users to easily find and connect to a wireless network in a typical wireless environment. In an environment in which there is a high volume of devices and numerous wireless networks, however, connecting to a desired network can become arduous. This is often the case in test environments set-up for customer demonstrations. Lab technicians at Cisco approached EDEC Digital Forensics with this problem, delineated by the diagram below. During field demos, Cisco’s sales engineers were constantly having to work through long network lists to identify the correct access point/s.

EDEC worked with Cisco to design and implement a solution to this problem. Subsequently, the solution garnered the attention of developers in the area concerned about exposure to strong near-field radiation.

Solution

As an innovator of digital forensics products, EDEC specializes in preserving digital evidence by shielding devices acquired from criminal suspects to prevent remote wiping and tracking. The physics behind keeping signals contained within our forensic bags (and preventing external signals from penetrating our bags) is identical to those employed in the Black Hole Test Bag.


EDEC developed a test bag that accommodates an access point antenna to be wired into our patented USB filtered faraday bag enclosure. The remote antenna set-up leaves the access point outside of the bag, eliminating issues related to overheating. Devices can be placed inside of the bag and provided with both power and data connections through a shielded, filtered USB cable, replacing the noisy environment of micro-networks shown above with the following architecture:

The shielded micro network that we have created, shields any devices inside of the bag from unrelated networks while simultaneously shielding the network in the bag from interfering with neighboring networks or other devices. The bag also reduces the near field energy of access points to a much safer level, providing developers with a safer working environment when prolonged exposure to the equipment is necessary.


Testing

Tests were conducted to demonstrate the performance of the bag in various environments. Close Range/High Power AP Isolation Test A small scale test was conducted with two Cisco Access Points to determine the effectiveness of the bag when in close range to other network AP’s. One access point had its antenna wired into the bag (labeled “Inner Bag AP-Target”) while the other access point remained outside of the bag (labeled “Outer Bag AP- Noise”). WiFi signal testers were created using two mini computers configured with identical hardware running Linux. Linux utility “iwlist” was used to scan for wireless networks and measure the relative signal strength. An appendix at the end of this document lists the code used for the test. One wifi signal tester was kept outside of the bag while the other was placed inside the bag forming a single node network with the target AP. Signal strength scans were performed by each wifi tester while the bag was fully sealed from signal penetration using our unique double rollover velcro method. Charts below illustrate the signal readings both inside and outside of the bag.

In the charts above, when the bag is closed (just after 19:18:00) shielded signals quickly drop off by nearly 50%. After further adjustment of the seal the shielded signal penetration was undetectable.


Multi Access Point Shielding Test The wifi signal tester from the previous test was placed inside the bag and allowed to record signal strengths from all networks in the area. At the start of the test, the bag was open. After a few baseline test points were recorded, the bag was sealed for several seconds. Just prior to ending the test the bag was opened to allow the signal tester to scan for AP’s. The results of the test are shown in the chart below.

Nearly all access points are cut off within the first 20 seconds of the test. Remaining signals continue to decrease in strength over time until only the target signal (blue) and the close proximity noise generating AP (red) were detectable. As soon as the bag is reopened, the wifi sensor re-acquires nearly all of outside networks.


Application Test with a commercial wireless device (iPhone) The bag was tested with an iPhone to demonstrate its performance in the intended application. The iPhone was connected to a computer via the bags filtered USB data cable and monitored using screen share software. At the start of the test the bag was open and many wifi networks were displayed (left image). The bag was sealed, and after a few seconds all wifi connections were lost (except for the target AP with antenna inside of the bag), and the phone was shielded from cell network reception, showing ‘no service’ (right image). A video recording of this test is available upon request.

Conclusion

The Black Hole Data Test Bag is an effective solution to the problems associated with noisy WiFi development, sales and testing environments in which numerous wireless networks are competing in one area. The adoption of Black Hole Data Test Bags solves the problem of effective device connection for sales demonstrations and eliminates adverse health effects of prolonged exposure to an environment that would otherwise have high RF energy. The adoption of EDEC Digital Forensics Data Test bags to isolate your WiFi network will protect the health of employees, improve product demonstrations, and work efficiency.


Appendix

The python script below was used to scan for wifi signals. The code is written to be used with the TP-Link Nano wireless adapter. Signal strength output notation from iwlist may vary depending on the specific hardware configuration running the code. This script must be run as root for real time measurements. import sys import subprocess from datetime import datetime essid = signal = "" while True: scan = subprocess.Popen('/sbin/iwlist wlan0 scan', stdout=subprocess.PIPE, shell=True).communicate() results = [] for line in scan[0].split("\n"):

if line is not None: if line.strip().startswith("ESSID"): if essid != "": print "Didn't get a signal reading for {0}".format(essid)

essid = line.split(':')[-1].strip("\n").replace('"',"") if line.strip().startswith("Quality"): if essid != "": signal = int(line.split('=')[-1].split('/')[0]) print "{0}- Essid = {1}, Signal =

{2}".format(datetime.now().strftime("%H:%M:%S.%f"), essid, signal) results.append(dict(id=essid, signal=signal)) essid = ""

else: print "Got a quality reading without an associated essid"

with open('results_all.csv', 'a') as f: f.write(datetime.now().strftime("%H:%M:%S.%f")) for result in results:

f.write(",{0},{1}".format(result['id'], result['signal'])) f.write('\n')


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