RF shielding

So we need to present together technical meaningful information and non-technical meaningful information so that when shown the layperson can follow it

I am clearly failing to see your point. ?

jaclaz it is not you, but me. I thought I understood your humour and thought you would see the funny side of the diagram. I was laughing with you, and most certainly not at you. Apologies for the misunderstanding.

Maybe with a fresh understanding of what I am doing with the diagram you can laugh with me.

For the record I am not disputing what you were saying. best regards.

jaclaz it is not you, but me. I thought I understood your humour and thought you would see the funny side of the diagram. I was laughing with you, and most certainly not at you. Apologies for the misunderstanding.

Maybe with a fresh understanding of what I am doing with the diagram you can laugh with me.

For the record I am not disputing what you were saying. best regards.

I find the diagram a very nice piece of work (and fun D ), nothing to object to it, as a matter of fact I like it, it is much in the style of "chain reaction" and or some of the best xkcd diagrams, here is an example flowchart wink
http//xkcd.com/518/

Sorry for not getting it as it was meant (a jokingly interlude while talking "seriously") oops

jaclaz

Hello,

Apologies for the late reply to this post, but I see that there are some questions about the NFI Faraday Cage. I work for the NFI at the department that has developed the Cage and would like to give some more details in answer to your questions.

- It is true that the kit is not easily portable (±12kg), but it is not intended to be, though police investigators can use the NFI Faraday Cage externally for transport and storage when large numbers of phones are seized. The NFI Faraday Cage is specifically designed to be operated at a police station to store, charge and read out mobile phones. We have plans to develop a separate, portable Faraday Cage for collecting phones, which can be placed and opened in this Cage. But first we focused on this Cage since it had more requirements a Cage in which phones can be stored, charged and read out securely.
- As for the weaknesses of other Faraday Cages/Bags on the market these tests were conducted using other commercially available Cages/Bags and are also based on feedback from the police. The weak points of the Cages, which are extensive, range from insufficient shielding by the gloves to quick deterioration of the lid seal to the absence of a filter for the electric inlet and a lot of other issues. Apologies, but this is not a published study. We did not find one Faraday Cage which complied with Dutch forensic standards.
- We have done extensive testing on the Cage, not only by simply looking at the signal strength that the mobile phone has while placed in the Cage and sending messages, but also by having it tested by an independent firm. Their findings show that average attenuation is higher than 72 dB in a range from 0.8 to 4.0 GHz.
- Some other points that you might be interested in
o We purposefully decided not to have a viewing pane, since this would introduce a weakness in the Cage’s structure. Instead, we made a camera feed available through a USB to glass fiber connection, which gives the opportunity to record the signal and for people in another location to be actively involved in the investigation by hooking into this signal
o We also used the USB to glass fiber connection to make data recovery from outside the cage possible, using XRY and UFED. I should be noted that UFED is not possible in all scenarios, in which case the UFED device needs to be placed inside the Cage
o The Cage can also be used for safely storing and reading out of WLAN-routers, laptops and handheld GPS devices.
o For transportation we generally advise the police to use aluminum foil, wrapped first neatly and then randomly around the phone, or a faraday pouch, though quality varies and of course it is not possible to charge the phone during transport in this way.
- Because we are a government institute we can only sell our Faraday Cages to government institutes.

Thank you for the information you provided.

o For transportation we generally advise the police to use aluminum foil, wrapped first neatly and then randomly around the phone, or a faraday pouch, though quality varies and of course it is not possible to charge the phone during transport in this way.

Basically this confirms that (for transport purposes) "common" Faraday bags can be effectively replaced by *any* integral metallic shielding, not completely unlike the result of this simple experiment
http//www.scienceoffcenter.org/science/462-cell-phone-faraday-cage

and that the "real issue" is the laboratory room/environment where you take the handy out of the tin/metal protection (to inspect, copy, etc.).

I see very little issues in having a "proper thickness" tinbox, similar to these (examples)
http//www.asia.ru/en/ProductInfo/488941.html
http//www.indiamart.com/darshanmetalindustries/small-case-with-hinge.html
http//www.indiamart.com/darshanmetalindustries/aluminium-sheet-metal-product.html

with some foam in it to have not the handy touch the tin and/or "rattle too much" inside it and have inside it a "universal" battery pack, not completely unlike these (example)
http//www.cellphoneshop.net/backup.html
http//www.voltaicsystems.com/offgrid-battery.shtml

And - this way - have an economical enough "evidence carrying solution", safe from the event of the battery discharging during transportation and also safer than a faraday bag (from the perspective of mechanical damages during transportation).

So, the question remaining open could be "how thick must the tin be?"

What if one plays "dumb" and uses instead a box like (still example) this one
http//www.northerntool.com/shop/tools/product_200343628_200343628
or one of those boxes designed to house (also) RF components?
Examples
http//www.rittal.com/com-en/product/show/variantdetail.action?categoryPath=/PG0001/PG0002SCHRANK1/PG0003SCHRANK1/PRO0019SCHRANK1&productID=1554500
http//www.rittal.com/com-en/product/list/variations.action?categoryPath=/PG0001/PG0002SCHRANK1/PG0003SCHRANK1/PG0011SCHRANK1/PRO0009SCHRANK1&productID=PRO0009
http//www.ce-tek.co.uk/cea-series-p-129.html

This one (which is a specific Forensic solution)
http//www.rfshieldbox.com/ste2200f.html
http//www.rfshieldbox.com/datasheets/STE2200F.pdf
Reaches

 Isolation
o -100dB @ 1GHz
o -90dB @ 3GHz
o -80dB @ 6GHz

with .90/.125" thickness.

Additionally (or alternatively) one could use fabrics like (examples)
http//www.lessemf.com/fabric.html#2272
http//www.lessemf.com/fabric.html#259

jaclaz

Jaclaz,

Contact me, I will send you a couple of samples of my bags. They work.

Simon
simon.steggles@disklabs.com
01827 50000
www.faradaybag.com

Jaclaz,

Contact me, I will send you a couple of samples of my bags. They work.

Simon
simon.steggles@disklabs.com
01827 50000
www.faradaybag.com

Thank you for your kind offer ) , but I would have no use for them.

I am sure they do work, but I expect them to work within the declared specs (and not exceed them significantly)
http//www.faradaybag.com/rf-shielding-testing.html

RF Shielding Testing

The Disklabs faraday bags have been fully tested both by Disklabs and independantly. The faraday bags reliably attenuate at 19dB for 900Mhz and 30dB for 1800Mhz and 2100Mhz.

Much of the point of this thread is about exiting "cold", "scientifical" data such as dB attenuation and provide "filed experience" and "practical tests" (besides providing more "layman level" scales).

We do have a "reference" paper that states verbatim (and coincidentally citing your company as source)

Many of the shielding tools available in the mobile forensics market have only one thin layer of mixed metal fibers designed to attenuate signal between 800MHz and 1900MHz bands, which is where mobile phones in the United States operate (Kessler, 2009). This means that many of the devices sold as Faraday containers are not really Faraday devices. They do block signal in a similar manner, but not as effectively allowing some signal to get through. The shielding tool can still function properly as long as its RF attenuation is greater than 50dB (Hill, personall communication, April 6, 2007). This number was determined from practical measurements that Hill conducted showing that the typical mobile phone does not have a 50dB margin of operation (Hill, 2010). According to Disklabs, a vendor for mobile phone shielding devices, 17dB attenuation through their bag is enough to isolate a mobile phone (Disklabs, 2008). This shows that there is little consistency for determining how much attenuation is needed to isolate a phone. The inability to attenuate all signals is where the errors from this experiment are expected come from.

In a nutshell the paper reports how different phones in a same bag behave differently and while a lower attenuation level may be enough to block voice calls effectively it is not as effective with different type of data (such as MMS and SMS, particularly this latter type).

Now 17 or 19 db (or even 30 db) are VERY different from 50 db and even much more different from the 72 db reported for the NFI cage.

Surely it may be enough for "common use" (I would personally say excluding SMS messages) but is it "100% safe"? ?

The other question being do the forensic investigator actually need such "100% safe" level (or a "good enough for common use" is actually enough)?

And the final question is "Set aside what is actually *needed*, what is the minimum attenuation providing this abstract 100% safe level?".

jaclaz

Apologies, but this is not a published study.

As a scientist, I find any statement that references research which is secret by design, highly suspect.

No need for apologies of course. Just publish the research.

Until then, I am sticking with a roll of aluminum sheet, a case of Campbell soup, and four copies of a Calculus tome.

I am still experimenting which soup is the best for this.

mrgreen

I am still experimenting which soup is the best for this.

mrgreen

Well, that is obvious, lentils! wink

jaclaz

Hello,

Jaclaz, thank you for your reply. It is indeed true that the real issue lies with the read-out environment, if the transportation device is (1) secure and (2) ensures that the phones stays charged. The third requirement to the transportation device is the possibility to place it, in its entirety, in the read-out environment to remove the mobile phone, otherwise this defeats the whole purpose of safely transporting it in the first place.

Having a battery pack would definitely fix requirement two, though temperatures in the tin box might become too high for the mobile phone(s) since there is no ventilation.

The transportation Faraday Cage is high on our list of R&D we’ll be looking into it now that we’ve fully developed the Faraday read-out Cage.

Jhup, “Not a published study” does not mean it is research which is secret by design, but it means that our conclusion is based on prolonged and extensive experiments with equipment available on the market, feedback from the police and taking into account that the sensitivity of mobile phones is continuously increasing. We are not an institute that develops standards for forensic tools, but we noted this deficiency in available tools for the police, which is why we have developed our own Faraday Cage.

Is your research available for peer review?

Where there non-interested experts reviewing the methodology and results?

Maybe it is a language barrier for me, as English is not my native language. I was under the presumption that "secret" meant that something is not known or seen or not meant to be known or seen by others.

What is preventing you from publishing it and redacting information? After all, you indicate the tools used are available on the market, and your processes are not new intellectual property.

Jhup, “Not a published study” does not mean it is research which is secret by design, but it means that our conclusion is based on prolonged and extensive experiments with equipment available on the market, feedback from the police and taking into account that the sensitivity of mobile phones is continuously increasing. We are not an institute that develops standards for forensic tools, but we noted this deficiency in available tools for the police, which is why we have developed our own Faraday Cage.

Never mind. Forget the whole thing. ?