Roger and Shub are all worried about Snowden, being tracked, yada, yada, yada. Roger sent me to a link where some guy was saying he didn’t own a cell phone because he didn’t want to be tracked. I suggested not owning a cellphone was just a bit extreme.
Anyway, tweeting continued.
It seems Roger (who after all has been raided by the Norfolk Constabulary) takes his battery out. I suggested he just needed a little aluminized bag him the snapshot of the inside of a cheap old bag. He sent me dimensions and made this prototype “Snowden Sack” from an old worn out refrigerated shopping bag: 
I’m hoping the design will block out all RFI and also permit Rog to use the flap as a reflector to amplify signal when necessary. I’m not sure if the latter will work well enough. The metalized fabric is not perfectly smooth. And as it happens, I’m just assuming the metallic looking fabric is aluminized. So testing is required.
The velcro is glued on; this design choice was made through the “winging it” method. Some durability testing is required. There is some evidence the ‘glue on’ method is sub-par. I want to avoid a buttonhole. Maybe a snap? (That said: If I wasn’t winging it, I would know in advance where I wanted the velcro so could plan for that when sewing. It’s easier to attach before seaming the sides. )
For those wondering: This is made from 99% recycled material. All except the velcro and thread are cannibalized.)
If anyone has design ideas, holler! I can add those to the final version. 🙂
Hmm… I think I need to announce UHA winners!
I really wouldn’t want to put a radio transmitter into a metal bag. I assume the phone will try (hard) to connect to a base station which would mean turning up the transmitter power which would then bounce around inside the metal enclosure — think microwave oven. Seems like not a GoodIdea ™ to me.
Removing the battery works remarkably well though. No power, no tracky.
Sorry if it was meant as a joke and I missed it.
bob
schoerkelman-
Do phones “try harder” to connect to base stations? Commercial silence bags exist.
http://www.amazon.com/SilentPocket%C2%AE-Suit-Shielding-Phone-Black/dp/B005Y6S73M That’s $65, but it’s a pretty large bag. You can find cheap ones too: $3
http://www.amazon.com/Gino-Anti-radiation-Phone-Mobile-Pouch/dp/B0058FDCA2/ref=pd_sim_sbs_cps_1
I’ve never heard of anyone having any trouble with the sorts of farady cage type bags causing phones any untoward problems. People also make phone shields from duct tape and aluminum foil. I’ve never heard of those causing phones any trouble.
Of course removing the battery works. But it can be inconvenient and now you have to be carrying around the battery and phone separately.
Obviously you take the phone out of the bag when you want to use it– just like you’d reinsert the battery to use it. But I’d personally find a little holder bag more convenient. Just shove the phone in.
The glue for the velcro isn’t holding though. I need to test with various phones. I think the mylar should be fine… but didn’t actually test.
lucia, some phones don’t even have removable batteries.
Lucia,
Some phones do boost the transmission power if the signal from a tower is weak, as the assumption is that the tower is beyond the phone’s range at the lower power level. I know this is true because I read it on the internet. 🙂
An effective Snowden sack would meet Roger’s aim of not being tracked. I wouldn’t have much fear of the phone in the sack doing anything other than trivially raising the temperature of the conductive material. As a bonus, a phone in boost mode will wear down the battery that much sooner, giving double plus good anti-tracking assurance.
Completely tangent to the tracking, the geophysicist in me is wondering whether any current induced in the conductive layer would be detectable with a sensitive coil. One could in theory measure the induced electromagnetic radiation and be able to detect a powered up phone within the range of the coil (ie, walking through the coil much like the metal detectors at airports)
Earl–
Interesting question. I assume you would place the phone and its Snowden-Sack in the tray when going through airport security as the purpose is not really to conceal the fact that you have phone, just prevent you from being tracked as you wend your way around the planet during your travels. (Presumably, for super-maximum security, you go through a series of disposable phones. Still, while you have a particular one you don’t want it tracked. Right?) Obviously, if you place the phone in the tray, someone will know you have a phone– or at least something– in the pouch.
Brandon
Yes. That’s one reason we need Snowden-sacks.
BTW: The fabric glue does not work. It says “made in china”. Maybe that’s the explanation . . . I’ll look for a different glue first. I like the idea of gluing the velcro on much better than a button. The fabric has padding type insulation on the other side of the metal film, so it doesn’t fold well. Otherwise, just letting the flap hang would be fine.
Have you thought about how you’d test whether it works or not?
Mostly by putting the phone in, calling and seeing if it gets through. Can you think of other tests?
You can kill frogs with cell phone towers:
http://www.ncbi.nlm.nih.gov/pubmed/20560769
Finally a subject I can authoritatively speak on!
Yes the Faraday cage will work (and it just has to be finer metal weave than the target wavelength) provided that there is an insulator between the cage and the phone.
If the phone does boost its signal it doesn’t have anywhere near the power to fry itself : ) They will all power down with no return signal. Or just turn it off before putting it in the bag.
If someone is really paranoid it is best to have two cell phones, one legitimate and easily tracked. Plausible deniability : )
Genghis–
Ahh! I didn’t think of an insulator between the aluminized film and the phone. Didn’t know I needed one!
That means I’ll need to add a pretty lining which is easy to do. Of course, if this is really for Rog, I need a “manly” lining. (Of course, if I’m going with cheap recycled, old sheets might do the trick. 🙂 )
Ghengis,
And when you think the ‘bad guys’ are after you, you toss the easily tracked one on some moving vehicle you aren’t in, right? (Back of a taxi. Tape to the side of a camper traveling to north of nowhere Wisconsin while you drive south to Chicago. Etc. Right?)
Ghengis:
Still something I’d like to see tested—I’ve run across paradoxical looking results when you get into the GHz range. For example, I put a wifi antenna inside of an aluminum box (like this) where the antenna is not in touch with the sides and still get good enough transmission through the sides to cause issues.
The antenna needed to be there as a “terminator” otherwise the amplifier for the WIFI overheated and burnt out… this is for an embedded LINUX system that had no mechanism (no “support” really) for turning off the amplifier. The system had to go on a military base where unattended systems that produced microwave radiation in the 2.4 GHz band were forbidden…anyway the transmission strength was “good enough” to disallow the system on their base.
We had thought, naively it turns out, that the aluminum would act as a good conductor at these frequencies.
Carrick, that’s interesting. Was your unit battery-powered and completely sealed within the box or were there holes for power cables and data lines to pass through? Did the lid fit well and seal hermetically? Your getting down to wavelengths around 0.125mm at 2.4 GHz so the microwaves can sneak out of some fairly small holes…
Roger/Talbloke was blocked by my spam filters and emailed me his comment
Roger–
I’m still going to “perfect” the Snowden-Sack. If nothing else, I can put my phone in it when I drive around. After all, I don’t want the NSA to know how boring my life is, involving trips to “Jewel” (a grocery store), “Butera” (another grocery store) and “Arden courts” (the nursing home. )
Matt, the box is water tight.
Have you done your math correctly though?
2.4 Ghz has a wavelength of 3e8 (m/s)/2.4e9 Hz = 0.12 m = 5 inches
I also have a steel tank that is 1″ thick that is almost transparent to microwave. That isn’t as surprising to me, given the poor qualities of steel for AC
transmissionelectrical conduction.Carrick–
That’s interesting. I don’t know enough about RFI etc. to optimize. But I am familiar with materials available in sewing shops, wallmart, or cannibalized from other goods. So, if you had to guess, which might be useful:
1) a polyester with flecks of reflective metal embedded in it? (Used to pot holders, hot pads etc. The stuff really has little metal flecks sort of randomly embedded in it. Gets sandwiched between ‘pretty’ scorch-proof fabric.)
2) Mylar film (as on the front side I show in the image.)
3) Grid of metal threads in a woven matrix of insulator (available for– believe it or not– parachute type applications. The threads are there for strength.)
Combinations?
Obviously, one wants a) cheap, b) lightweight, c) easy to sew or assemble and also d) not butt ugly.
Lucia:
If you have access to a MIFI device, or if you have a phone that can operate as a mobile hot spot (so you can log onto it from a computer via its IP address), you could look at the SNR of the tower with the device inside of the bag and compare it to the value when the device is outside of the bag.
Hmm.. I don’t have one. But clearly, this requires testing.
For most people, I think “phone doesn’t ring” is probably enough. But Roger actually *has* had the Norfolk Constabulary at his door. So not all people are “most” people.
I’ll ask Roger what he has. I can make a couple of cheesy prototypes. (The bag can be cannablized to make at least 20 of these. And making prototypes takes less time than cannabilizing. Final versions won’t take long either– but I need to have a nice closure. (I also don’t know if the flap is worth it. Roger mentioned that if signals are weak, you can put your device perpendicular to a metal sheet and improve signal. So I figured, why not design to have that if possible? (Of course people can just carry around a roll of aluminum foil. But still.. as long as something might be dual purpose, why not make it so? )
Matt I forgot to comment on this–“Was your unit battery-powered and completely sealed within the box or were there holes for power cables and data lines to pass through?”
There were holes for power cables and data lines and the batteries were external to the enclosure and the power cable was hooked up at the time (of course).
That is potentially an explanation, though in terms of the principle of a Faraday cage it isn’t obvious how that transmits a signal through.
It would be easy enough to repeat the experiment with a box that is unmodified and a MIFI device.
My suspicion is, were you to enclose the electronics in a “high quality” Faraday cage bag in the interior space, none of the other would matter. In other words, it is my guess is it is the aluminum that is the problem rather than the geometry.
Lucia, I just noticed there is a firm that sells similar devices. Assuming they actually work, it might be useful to start with something like that as a model.
One thing to be careful about is GPS tracking can be possible even when a phone doesn’t have service. You could find yourself in a situation where nobody could track you via cell towers yet your location was perfectly obvious via GPS.
Why sack? It should be ‘Roger’s Snowden Pouch’, or ‘Roger Custom Snowden iPhone 5 Case’.
Shub-
Consonance.
Carrick
The lid on the aluminum (even lapped and water tight) box is the obvious culprit (aluminum oxide is not very conductive), next are the screws, reusing the screws even one time will let out quite a bit : ) I doubt you would have had any issues with a copper box.
That is assuming that you have good grounds on the coax cable going in and a ground to the box.
Couldn’t you have just used a dummy load instead of an antenna?
Lucia,
Carrick is right, test it and use copper and make sure that the open end of the sack can be folded more than 360 degrees.
And remember you are trying to only block communication with the cell tower, that is trivial. Completely eliminating all RF is not worth the effort.
Test it by calling it.
Genghis,
That’s why I need the velcro. I can weigh down during testing tomorrow. But I figure I’ll either need the flap to go all the way around or most of the way.
The product Carrick linked to used conductive thread and conductive velcro. Wow! (I figure that’s probably not necessary. But we’ll see during testing.)
I think you’re neglecting the skin effect. For a faraday cage effective at microwave frequencies I think you need to use a metal that has a conductive oxide like silver or that doesn’t significantly oxidize like gold. Otherwise the penetration depth won’t get past the surface oxide layer. Maybe.
Interesting notion. A non-conductive oxide shouldn’t interfere with the skin effect – the “skin” starts underneath the oxide, in the proper surface of the conductive metal. A semi-conducting oxide OTOH may behave differently. Microwaves have other modes of interaction with non-conductors – I have a coffee mug the glaze of which becomes uncomfortably hot if placed in the microwave.
A commercial aluminium-bodied Faraday cage for use up to 6 GHz can be seen here: http://www.lbagroup.com/es/products/faraday-cages-emfaracage
This implies to me that at high frequencies, cabled connections give leakage problems.
Why don’t we put a sack on all governmental receiving equipment instead of our transmitting ones?
There are journal articles available which describe reflectivity of thin metallic films in the microwave range; apparently the thickness must be significantly greater that the free electron path length in the metal or the conductivity of the film decreases along with its reflectivity.
.
Carrick,
My experience is that any wire or cable connection, unless very carefully filtered, leads to a surprising rate of leakage (both in and out).
From Rog/Tallbloke (whose use of anon. services gets him blocked!):
Rog/Tallbloke,
I do think people who want privacy do need to take some of the steps themselves. Alas…. by the same token, I end up blocking many who use privacy services to visit the blog because, like it or not, script-kiddies, finger-printers and various hackers know they want ‘privacy’ and use the exact same privacy services (including, of course, TOR which is free). Ahhh…well…
But a ‘Snowden Sack’ to haul a cell phone around is useful for a number of reasons.
shub,
Because the government has been getting orders to force private entities (e.g. Verizon) to hand over records. Obviously, if you put a sack on all Verizon equipment, no Verizon customers will have service.
Besides, it’s not just the government who might track you. In airports and malls, some people use reading devices to try to detect credit card numbers and so on. (See http://www.katu.com/news/problemsolver/121550239.html ) On the one hand, you don’t want to be paranoid. On the other hand, it seems it might be wise to have various ‘sleeves’ for these things especially when protection could be as easy as cutting out a piece of foil the size of a dollar bill and sliding that into your bill fold.
BTW: I tried to make a bunch of the points about what would happen if Snowden returned to the US during my Twitter conversation with Shub and Roger. Some are also discussed here:
http://www.lawfareblog.com/2013/07/what-happens-when-we-actually-catch-edward-snowden/
* Potential for jury nullification “Jurors might be tempted to acquit Snowden, not because they believe he is factually innocent but because they believe he was morally justified.”
* Snowden would get pro-bono lawyers: “Snowden would no doubt obtain high-powered lawyers. ”
Obviously, returning to the US also means risking jail time.
“Jurors might be tempted to acquit Snowden, not because they believe he is factually innocent but because they believe he was morally justified.â€
This is arse about face. We’re not interested in the outcome of Snowden being prosecuted. We’re interested in the outcome of the prosecution of the Government which committed the crimes he has blown the whistle on.
Everyone knows they are crimes, but no-one seems to have a clue how to make the government accountable for their actions. They are criminals, prosecute them!
Lucia,
That is an interesting article. I think the current administration and key Congressional committee chairs don’t share the author’s views of the proper balance between realpolitik and deterrence of future potential leakers. If the Administration can grab Snowden, then I think he will still be sitting in prison when current political leaders are long gone.
Say what Rog Tallbloke? I don’t know that there have been crimes. In fact, I’m fairly sure there haven’t been. Just who is this “they” you want prosecuted? And on what charge?
And what do you mean we’re not interested in the outcome of Snowden being prosecuted? I’m interested. lucia seems interested. I’d wager lots of other people would be interested too.
I don’t think you should project your thoughts and feelings on everyone else.
Genghis:
I’ve thought about copper plating the interior of the box, but the need has passed. (We now are using a single-board computer that doesn’t have wifi built in for these applications.)
I would have liked to. I couldn’t locate a proper terminator at the time that met the physical constraints given the amount of time and resources we had available to pursue other alternatives at that time.
SteveF:
I’ve thought about that too. I think it goes under the rubric “evanescent mode coupling.” The E&M wavenumbers interior to a confined space can be much larger (wavelengths much shorter) than for free space of course.
If free time ever comes around and reintroduces itself to me, I will try the MIFI SNR test on a sealed box with no perforations and compare it to a box with cables attached.
My suspicion is in this the external cables won’t have a big effect, because the cables are shielded, with the braided shield connected to the case. The wires for power interior to the case are not shielded so that could be a potential source of leakage.
(The communication wires all have braided shields so again I’d guess this isn’t a problem).
Speaking of whistleblowers here is an interesting case. “Gallup Agrees to $10.9 Million Fraud Settlement, Whistleblower is Awarded $1.9 Million”
Another is here. Video: Did the IRS target a DHS whistleblower?
For the record I think Snowden is a misguided idiot, but I’m willing to change my mind. This case illustrates how little real vetting is given to contractors, in some cases, before they get access to top secret information. Bradley Manning (the Iraq whistleblower) is another case that comes to mind.
Carrick,
The article you link to says:
“The IRS insists that audit decisions come from careerists at the agency, and politics don’t play any role in enforcement. However, that was their position on allegations of targeting Tea Party groups in their applications for tax-exempt status too, until it finally fell apart during an IG audit. After that got exposed, the IRS insisted that the targeting only took place among “low-level employees,†but later testimony showed that to be false.”
.
If anyone is still thinking the current administration does not use the levers of power to advance its political agenda, then that person is kidding themselves. If Mr. Obama wants to stop the IRS shenanigans, he can simply instruct Eric Holder to prosecute all the “low level”, and not so low level, IRS employees who have been involved. He is not going to do that. I believe that the administration considers intimidation of individuals (including potential leakers!) and political opponents through exercise of government power to be important and useful, even at some political cost, and so not something he is going to stop. After all, Mr. Obama is a creature of government, and clearly believes that government is more capable of making the ‘correct’ decisions about most things than are individuals; he will never support anything which reduces government influence over individual choices. Only 3 1/2 more years… 1 1/2 if Senate control changes hands.
lucia
My question was rhetorical, just as your sack was.
Snowden revealing the NSA’s scale of operations deserves prosecution? For what?
Snowden is immaterial, if the NSA’s doing what he says they are doing.
I think sometimes issues such as those developed by the person of Snowden and those in the IRS (and perhaps Obama administration) get lost on characterizing the people involved. Snowden, regardless of his character and motivations, has revealed some government secret going-ons that can now at least be debated if not abated. That the IRS (personnel) can arbitrarily inhibit the speech of a political group has to be troubling and much more troubling than the MSM portrays it. If this IRS action can occur within our government and for as long as this one did without the knowledge of an elected official it becomes to me even more troubling than if one evil person was the culprit.
It almost appears that we want to avoid talking about the major sources of these problems i.e. big government out of control.
Kenneth
Agreed.
There are people who want to talk about that. 🙂
SteveF–
I am sure that if the current administration gets their hands on Snowden, he will be charged aggressively and tried. There is no doubt about that. He did take information and leak it– which violates the letter of the law. The administration certainly doesn’t think he was right to do so. They will charge to the maximum extent possible.
At various places people are speculating about strange things. For example in comments at one guys is speculating trial would be not be public. I’m not sure how that could happen. (And Orin Kerr– the law professor who wrote the blog post asked the person suggesting the possibility how it could happen. )
On the other hand: Jury nullification does happen. It’s pretty rare and, alas, I think when it happens, it’s not necessarily in the more appropriate cases. (It used to sometimes happen when all white juries would not convict a white guy for crimes against blacks, for instance.)
It remains rare for many reasons including the fact, jury instructions don’t include a bit that says, “BTW: we’ve instructed you about the law and told you that it’s your duty to apply it— possibly even going so far as to tell you that it’s not your right to decide the law is unjust yada, yada. But the fact of the matter is that, when push comes to shove, a juror can vote ‘not guilty’ for whatever the heck reasons he wants to do so. And, moreover, if they do, there is nothing remotely illegal about that. Not only that: this behavior has a name: ‘jury nullification’ and it’s reality is as old as our government system.” So, I think often, it doesn’t even begin to occur to jurors that they could nullify. But they can– and sometimes do. It could happen with Snowden but of course, I doubt he or any attorney would rely on it.
Carrick
I have very mixed thoughts on him. I am on the one hand glad that public discussions of monitoring are happening. What the limits are, broad outlines of the sorts of things collected and retained and the sorts of controls in place to limit invasions of privacy are all things people should be aware of. (And really, people ought not to be too naive. Obviously, if you carry around a cellphone with apps to connect you to “everything”, then you are connected to “everything”. For example: It’s not just the government, Nordstrom tracks shoppers. )
On the other hand: some things about Snowden definitely seem to put him in the ‘dolt’ category. The exit plan was China? Then Russia? Really?! Was there every any thought given to doing stuff anonymously? (Maybe not possible?) And there is the issue that he seems to have taken the job with the intention of leaking as opposed to discovering what was going on, getting upset and then deciding to leak. That’s not normal ‘whistleblower’ behavior even if one likes certain outcomes from the leak.
(Just to make Shub and Rog angry… I think to some extent, Snowden’s motive is that he wants or wanted notoriety. If so… well he got it. He’s probably seeing the downside now.)
BTW: It looks like he did finally apply for temporary asylum in Russia. We’ll see what happens. My prediction is that he’ll get ‘temporary’ refuge. Putin is not happy with all this… but Snowden will get temporary refuge. That will give him room to breathe, get papers and sneak off to somewhere that will give him asylum. (And honestly, he better sneak off fast.) I predict he will end up in .. hmmm I pick Tegucigalpa.
BTW: To attorneys who blog at the volokh conspiracy are debating the 4th amendement and collection of meta-data
Orin Kerr: http://www.volokh.com/2013/07/17/metadata-the-nsa-and-the-fourth-amendment-a-constitutional-analysis-of-collecting-and-querying-call-records-databases/
Randy Barnett: http://online.wsj.com/article/SB10001424127887323823004578593591276402574.html
(Some will recall I cited Orin during climategate — he had previously discussed whether posting leaked emails was legally ok. Randy Barnett was one of the attorney’s who took the Obamacare suit to SCOTUS. Alas… he lost due to the whole ‘tax’ angle. But a number of his points were adopted as correct.)
What are the mechanisms for tracking if the phone is simply turned off?
-I assume no power can be used to actively send out a signal, which to me would seem to eliminate cell phone towers.
-A GPS system needs to run calcs on the device for the user to employ (from what I understand). This would seem to be defeated if the phone were off. But could the owners of the satellite network still sense the device?
-Is there a possibility of a ‘false’ off-mode, where the phone screen and all controls are muted, by processes are still being run?
-Is there a way a local wireless router could ping the wireless card for the phone without the chip being supplied power? How about Bluetooth and NFC?
SUT–
That depends on the phone. For some phones, “off” does not mean “totally unpowered”. It’s more like “off” for my microwave or coffee maker. The clock on these still displays. If I want to turn them fully off, I need to unplug them (which I don’t do because they I would need to reprogram the clocks!)
Absolutely. In fact: that’s what “off” often means.
I don’t think so. That’s why removing the battery works.
SUT-
With high probability, nope.
Well, the guys who write software for cell phones generally don’t have to have security clearances or anything like that. I’d think it’d become common knowledge if this were the case; they’d talk about it. (UPDATE – not trying to contradict Lucia, I just doubt there’d be secret ‘find me’ code sending pings out while in off mode)
No, not without the chip being supplied power. In fact it’d take more than that, you’d need some sort of logic running on the device to produce a responding ping packet. This said, modern FPGA’s and ASICs let you introduce sophisticated logic at a pretty low level if you care to. I can’t speak with confidence to Bluetooth or NFC right now, but I doubt it.
SUT –
Are we talking about GPS or some other satellite network? I don’t think GPS works that way – don’t think those satellites ‘listen’ per se. Certainly they don’t need to for the GPS scheme to work.
Could other satellite networks detect a cell phone? That’s harder to say with confidence. I don’t know.
SUT – more plausible to suppose that the phone in ‘off mode’ is sending a signal to cell towers than a satellite, now that I’ve thought about it for a minute. 🙂
And the problem with my argument about word getting around is this – if there is some seemingly innocent reason for a phone in ‘off mode’ to communicate (say, checking for updates or something, don’t know) then their would be no particular reason for the developers to remark on the feature. If there is a way to track a phone in off mode, maybe it would take advantage of something that wasn’t originally intended for tracking…
Thanks all, it seems the conclusion is no tracking is possible then on the classic grid if the phone is ‘truly’ off, as neither towers nor satellites would recognize the device.
So is the phone truly off when powered down? Lucia describes ambient power in appliances. My critique is these are plugged in, whereas if I turn my phone off, I expect to have power in my battery when I turn it back on.
Could ambient power mode go to full (enough) boot mode?
Mark Bofill (Comment #117755)
“the guys who write software for cell phones generally don’t have to have security clearances or anything like that. I’d think it’d become common knowledge if this were the case; they’d talk about it.”
It’s strangely dissonant how Richard Stallman then is disconnecting his battery from his phone. Isn’t this guy a key figure in Linux, which runs Android?
But as you say, why hasn’t any hacker done this then? It’d be a great trick to turn on your friend’s phone when they go into an important meeting.
Finally on NFC, you can communicate with a chip with no power, e.g. inside a business card (http://us.moo.com/nfc/) but this range is within inches I believe, so there would need to be a very granular cell network to enable tracking.
SUT – wow, I need to quit chewing up Lucia’s blog space and get back to work, but you’ve got me thinking about this now. You don’t even really need GPS on the phone at all to get a relatively close fix, just the cooperation of the company that owns or runs the cell phone towers. Obviously, the system knows how to route calls to you (or can figure it out, same thing) and ultimately has to route data through a tower, so certainly they could place you within a grid cell around a specific tower at least.
Okay. I’ll quit the excessive posting for now. 🙂
SUT –
Yeah, I’m talking myself out of this position it seems. Now that I’ve thought it through it’s not as inconceivable as I first thought…
Roger sends this
Rog Tallbloke, I don’t think you actually addressed anything I said. As for your disbelief, it might work out better if you didn’t call government’s collection of data from company’s, with those company’s consent, “purloining.” That seems like nothing more than petty rhetoric used to inflame people.
Government agencies collect data from companies all the time. They do so with those company’s knowledge and consent. The fact those companies may not have a choice in the matter (due to the legality of things like search warrants and subpoenas) does not make it stealing.
luca:
I think that’s true for most phones, not just some. I know only some phones can be tracked while “off,” but I think most have a couple small things like a digital clock run all the time. I might be wrong about that though.
Televisions are the best example of what you’re talking about though. I don’t think any television manufactured in the last ten years truly turns “off.” You wouldn’t be able to turn them on with a remote if they did.
Mark Bofill:
These won’t let a phone company (or government) track a phone remotely if it has no power source. The distance is too great.
Though now I’m curious if one could design a system where a device would use its RF field to feed power to a phone’s NFC chip which would then be leeched off to feed some higher functionality of the phone.
I’m not sure how much power could be leeched off in that way so I don’t know what could be done with such a system. What I do know is you could generate RF fields for it with transmitters in buildings (a similar thing is already done in many stores) or with a small portable transmitter. That part would be really easy to do.
Lucia,
I would be very surprised if the administration attempted to try Snowden out of public view. The Sixth Ammendment says:
.
“In all criminal prosecutions, the accused shall enjoy the right to a speedy and public trial, by an impartial jury of the State and district wherein the crime shall have been committed, which district shall have been previously ascertained by law, and to be informed of the nature and cause of the accusation; to be confronted with the witnesses against him; to have compulsory process for obtaining witnesses in his favor, and to have the Assistance of Counsel for his defense.”
.
Hard to see how a non-public trial based on claims on national security would ever pass muster; the documents are all out in the open or soon will be. Snowden’s lawyers would no doubt lick their chops at the prospect of challenging a non-public trial in appellate courts and at the Supreme Court…. and they would likely take the case. Aside from the legality of a non-public trial, the whole thing would be a political disaster for the administration. Mr. Obama is not that dumb.
.
If they get a hold of him, it will be a public trial and they will ask that he spend much of his life in prison, and he probably will.
.
IMO, a jury is unlikely to nullify the law unless it comes to light that the NSA has been reading emails and/or listening to phone calls; my personal guess is that for emails this is probably routine (there are too many legal precedents on listening to phone conversations), but I would be shocked if reading of emails ever became public knowledge. If that ever happened, then all bets are off on Snowden: a jury might very well acquit, no matter the specific violation of law.
Brandon
It is a cool idea. Current draw isn’t really my area of expertise. I read over here that ultra low power chips can be had that consume 40 microamps per Mhz (wow, didn’t realize we could go that low!) so if we were willing to drive a slow processor it might be feasible.
I don’t know about a cell phone transceiver though; to communicate with a tower 10 miles away at a fixed set of frequencies would have to take a certain fixed amount of minimum power.
Footnote – I’m under the impression that most processors I’ve worked with at least draw milliamps during normal operation and usually don’t get down to microamps until / unless they’re in sleep mode.
Uhm, I meant to say I read over here (http://www.ti.com/lit/sg/slab034v/slab034v.pdf) that ultra low power chips…
Sorry, got interrupted while posting. ~blush~
SteveF
Yep. If he comes back to the USA, he’ll be charged and the trial will be in public. But I think he’ll end up in Tegucigalpa! If I were him, I’d pick that over Bolivia because Morales is too unstable (politically and mentally). I’m not sure about Venzuela.
On the “sack”…. the aluminized film must be too thin or not enough metal or something. I have various other things to try.
I wonder how the exposure of the fact that VERIZON has been handing over their customers data to the spooks is working out for them in terms of new contract numbers.
Brandon:
“The fact those companies may not have a choice in the matter (due to the legality of things like search warrants and subpoenas) does not make it stealing.”
Those companies are also being told not to tell their customers (as if they’d want to).
But regardless of the legal subtleties , my basic point is:
If secret blanket surveillance of the public by it’s paid servants isn’t unconstitutional, it should be. Otherwise, you can be sure that when the state decides it’s time to shut up the climate sceptics or any other minority group, they’ll be using secretly gathered ‘evidence’ with which they can silence them. This is bad for liberty and democracy.
Speculating about Snowden’s motivations is just a distracting sideshow compared with the important issues at stake here.
Aluminized mylar attenuates hut does not block GHz radiation. The heavier the aluminum the stronger the attenuation. Complete blocking would require a conductive material on the order of a significant fraction of a wavelength (IIRC).
Rog–
I bet Verizon’s sales are barely impacted. Among other things, people all suspect other carriers records are also requested. So that’s a wash. Plus, people likely go by price, coverage, plan and so forth. Those who really, really care (in the sense of ‘right now’), will go to the trouble of buying disposable phones and so on. It’s the minority.
Lots of people care that they are monitored– but not necessarily to the extent of taking steps as individuals.
Thanks Lucia for the insight. It seems the US is sleepwalking into totalitarianism.
Scary.
Re: SteveF (Jul 18 05:04),
Take a look at the door of your microwave oven. The RF shield is nowhere near centimeters thick. It even has holes in it so you can see through it. And the attenuation factor is many orders of magnitude.
The key is that the holes in the shield are much smaller than the RF wavelength, not the thickness of the shield. And it’s the conductivity that’s important. A superconductive film of almost any thickness would be a perfectly reflective surface for any RF frequency. But since room temperature superconductors aren’t available yet, you can only attenuate, not eliminate. The induced eddy current will show up at some reduced level on the other side of any conductor with finite resistance.
There’s an urban legend, btw, that you can test the shielding on your microwave oven by putting a cell phone inside it and dialing the cell phone. See: http://message.snopes.com/showthread.php?t=67936
Rog
Whether it is or is not unconstitutional is being debated. Obviously, back in 1789 or so, those writing the constitution didn’t word the 4th amendment as as “there will be no blanket surveillance of the public”. So the issue is: (a) exact wording, (b) how the 4th amendment might interact with other amendments. The 4th reads:
So, some debates I read entail deciding if this is “unreasonable”, whether it’s “a search” or “a seizure”, and then whether the permission to get material is a “Warrant” or a “subpoena”. Orin Kerr really is a good blogger to read on this. See Orin’s more recent post. He discusses how current precedents interpreting the 4th amendment to telephone records seem to apply and also how more recent arguments about something called the “mosaic theory” for the 4th amendment might apply. (You seem to be making a statement about constitutionality arguing for what Orin calls the “mosaic” theory, which Orin describes as “he collective acquisition and analysis of information about a person over time constitutes a search even if collecting individual discrete pieces are not searches”.)
The thing you need to be aware of with application of any constitutional provision is that clear precedents generally do not exist for behaviors that were previously impossible to implement. So, in this case, whether wholescale collection and storage of “metadata” is or is not a violation of the 4th amendment is something that has never been decided.
Well… that doesn’t necessarily mean the behavior has to be deemed “unconstitutional”. Congress can also tailor laws to not permit the executive branch to do this. (The NSA and most agencies operate under the executive branch.) In fact, some congresssional reps think it was not permitted. Hearings are ongoing see report on yesterday’s congressional sessions.
The NSA’s argument is not simply that their monitoring is merely ‘not unconstitutional’. The NSA (or anything in the executive branch) can’t do anything and everything it wants merely because that behavior is “not unconstitutional”. The behavior has to be specifically authorized. They are claiming that the surveillance is both “not unconstitutional” and it was was specifically authorized by Congress through the Patriot Act.
The authors of the Patriot Act seem to disagree with the NSA’s interpretation of the Patriot Act. (e.g. Sensenbrenner) (You’ll also see Conyer’s pretty much states the “mosaic” theory or the 4th amendment to wit “metadata collected in such a super-aggregated fashion can amount to a Fourth Amendment violation before you do anything else,” )
Maybe. But people are also speculating he is a “hero”, or “traitor” or whatever. In any case, speculating that the President of the US should be jailed is an equally distracting sideshow. That’s not going to happen. This is particularly so because there is a colorable argument that
(a) a person reading the the patriot act could believe it authorized collection of metadata and
(b) there were no clear pre-existing precedents indicating it was unconstitutinal. No one operating in the executive branch– from the chief executive (i.e. President) on down to the lowliest appointee operating in the executive branch is going to be charged or jailed for ‘mis-understanding how to apply the 4th amendment to behavior that has never been adjudicated’.
Even if you don’t like the outcome, the most one can hope for is that something akin to the “mosaic theory of the 4th amendment” would be developed, presented to SCOTUS and somehow defined by some as yet to be applied ruling in this case and that future monitoring of this nature would end. ( We can, however, be sure that some sort of monitoring would be permitted. The question is what type?)
The place where Snowden’s leaks do play a very important role is that some of the types of monitoring are now not in the “hypothetical” category. Instead we have some evidence they actually happened. Being ‘real’ and not ‘hypothetical’ is essential if a case is to be heard at all by a court (otherwise I think the term is ‘moot’.) Moreover, because the Verizon order was for 100% of records, some real honest to goodness plaintiff can bring forward evidence that their (not someone else’s ) records were requested. (As opposed to someone claiming that because monitoring was “broad” they are “worried” their records “might” have been monitored. I’m under the impression someone tried that pre-Snowden and the courts turned them away.)
I suppose that a lot of us depend on flying below the radar for our protection from misdeeds and overzealous intrusions by the government. But that “lost in the mass of information” approach may not work for those, like Roger, who do things publicly.
I suspect that nothing good can evolve without public action, so it does seem likely that those who go out on a limb equip themselves to better resists monitoring than the rest of this.
I find this whole thing very worrisome. I was encouraged by the apparently universal outrage over the IRS giving the conservative groups an especially hard time securing pre-blessings for their tax status which they apparently didn’t realize weren’t necessary.
It’s the old story, just as freedom of speech is a right which few exercise or even appreciate, freedom from government monitoring is another which only some of us will dread.
Regrettably, it is usually the people who help improve things the most for the rest of us who really need protection from government misapplication of power.
j ferfuson
I think we should be largely free from government monitoring. But with respect to picking Verizon as a carrier: The government probably requested ATT records and so on. So as a consumer, it wouldn’t affect my decision so much. If I were very concerned about monitoring of my activities and wanted a phone, I would to to the trouble of having disposable phones. But there is a large nuisance factor associated with that.
I’m much more worried about the IRS than the NSA. Apparently, if you’re a US citizen, you’re required to file a federal income tax return every year even if you haven’t lived or worked in the US for decades. There are substantial fines and penalties for not filing even if you don’t owe any taxes. It’s called FATCA, the Foreign Account Tax Compliance Act. Imagine that you were born in, say, California, but moved away early in life. If California had the equivalent of FATCA, you would be required to file California income tax returns for the rest of your life. A lot of ex-pats with dual citizenship have formally renounced their US citizenship to avoid this. That requires filling out forms and paying fees too.
Only one other country in the world, Eritrea, has a law like this.
Hmmmm, just saw this thread. Here is an elementary question for you advanced physics folks. Please pardon my ignorance but isn’t an earth ground required in a faraday cage design in order to fully neutralize the RF energy? It seems in designs I have seen for fully shielded rooms the cage was always grounded and the designer said this was an important feature. Just curious.
I have become rather cynical about the protections of individual freedoms that are afforded by the US Constitution and as interpreted by Supreme Court judges. It appears that over the years the Constitution has become whatever 5 Justices might say it is at a given point in time. Therefore I get no comfort when there are those who might argue that NSA and its activities, secret as those activities might be, are constitutional. I see those blogs that argue the constitutionality of these issues, that get current coverage from the media, as game playing without ever making a statement about some ideal for safe guarding individual freedoms or for that matter where the constitution and its interpretation are wrong or contradictory.
I really get concerned when I hear media political pundits referring to the ideal of democracy as though democracy alone, and without mentioning protections of individual rights, is that which all nations should be striving. The recent fiasco in Egypt, which borders on democracy one time one vote, is an example of legitimizing to at least some media types and members of the intelligentsia some rather awful infringements on individual rights just because a vote was taken. Amongst the world intelligentsia I see this ideal of democracy without a guarantee of rights as almost universally accepted.
Re: ivp0 (Jul 18 08:24),
No. A Faraday cage works by reflecting EM radiation. Grounding isn’t necessary for that. The conductive plastic bags in which electronics are shipped aren’t grounded. They’re not very good Faraday cages because the conductivity is low, but they’re good enough to keep static charges from getting inside.
Here’s an interesting comment I found on Faraday cage leaks:
Re: Kenneth Fritsch (Jul 18 08:49),
I find it highly ironic that an organization whose stated goal is to eliminate democratic rule and restore the Caliphate is complaining that their removal from power was undemocratic.
ivpo–
The snowden sack was a failure. I was overconfident and spent 15 minutes stitching when I should have just done various “wrap/test” operations. I’ve now done the following tests:
1) Place phone on table, dial: Phone rings.
2) Place phone inside an all clad frying pan with lid on top to form good seal. Dial: Phone does not ring. ( Tested both wrapped and not wrapped in paper towel: makes no difference. So, at least with my phone, no external insulator required. )
3) Remove lid. Phone rings.
4) Replace lid with two aluminum pie plates that contact pot. Phone rings.
5) Weight down pie plates with lid to press pieplates to all clad pot: phone rings.
6) Wrapped phone in old torn aluminum foil: phone rings. ( My roll of foil happens to have run out. So, I had to use a piece I’d used as a heat shield on the top of my slow cooker. I’d cut out a hole for the handle… so hole….)
I’m going to get some more alumimum foil. I also have some assorted other things. Clearly, SteveF is correct about thickness. I don’t know whether you might not be correct about grounding, but if you are, it’s possible that we can add a ground strap and see if the person toting the bag represents sufficient ground. They might. People are pretty conductive — though probably not if they wear sneakers or rubbersoled shoes!
Right now I don’t think the problem is grounding though. The aluminum foil is just as well grounded as the cooking pot.
Thanks for the response DeWitt. I had previously thought that the cage was not just reflecting RF energy but actually absorbing it and shunting to ground. Good to know.
DeWitt:
If you have electronics in the interior (wires passing through), though, it does need to be grounded. Otherwise the external case case have a different potential than the grounded case for the electronics, and that can produce electronic noise.
Incidentally, the Faraday cage Wiki page is one of the worst write-ups I’ve seen on the Faraday cage principle. It is like they used a high-school physics textbook as a reference.
Kenneth
I think it’s important for law blogs to discuss what the law is in addition to what it ought to be. After all: if the law differs from what it ought to be, we need to know that both so we know how to protect ourselves and so we can take steps to change it. Otherwise, there is no magic mechanism to change bad laws with evil consequences into better law.
I think there has been a lot of discussion about Egypt, democracy and such like. Back to the same law blog where Orin blogs, you can read what Ilya has to say:
http://www.volokh.com/2013/07/08/more-on-egypt-constitutionalism-and-democracy/
Ok…. I’m going to go get my hair done. Afterwards, I’ll go to the grocery store and buy:
1) More AL foil (heavy duty).
2) Copper scrubbies.
3) Stainless steel scrubbies.
4) Various other cheap things that look like they could be easily incorporated into a sewn design (or fused to fabric using something like “stitch witchery” or various types of glues.)
Of course all these things can be used around the house. But now I want a cheesy “Snowden-Sack”. (I know we can buy these things. But I can make this craftsy.)
The government does watch you if you somehow bring yourself to their attention. We were visited by an extremely courteous FBI agent 40 years ago who had been assigned to visit based on an overheard conversation I’d had in a restaurant with a friend of mine about what you would need to accomplish a particular type of event, how you would cause the event, and what its effect might be. It was academic, but we must have scared the #@$% out of whoever heard it.
I got a pass from the agent and didn’t hear about it again until I was up for a letter clearance in the mid ’80s. I got to spend a day with two DIA guys who nipped all around the thing that was apparently worrying them without saying what it was, and then when i asked specifically if it was the old FBI report, they caved. I was able to allay their concerns.
I wouldn’t at all be surprised if one were repeatedly indiscreet in his or her choice of words either on-line or on a cell phone, a file could be created and more directed monitoring would ensue.
I hate it, I think there should be a sunset on information accumulated on anyone who doesn’t do anything overt, and the government’s authority to watch and collect information on us severely restricted.
A guy who calls himself Petrossa over at EM Smith’s site went into some detail a while back on data collection, coordination of data collected from different sources, and its use in harassing citizens in the Netherlands. It got bad enough that he moved to France along with a LOT of other Netherlanders.
Stuff like getting stopped by the police for speeding, caught by camera and speed trap, and then finding oneself waltzed off to the slammer because another agency of the government has noticed that you use twice as many gallons of water as your neighbors, don’t have a hair-dresser license or pay the appropriate fees, with the assumption that this must be where the water is going.
we are within days or maybe months of the government being able to data-mine all the databases they can think of and look for patterns. I suppose I can’t really blame them, it would be very interesting, but their ability to do anything about it must be severely restricted. A lot of us live in the interstices of their regulations and enjoy our respite from lunacy – and oppression.
“I think it’s important for law blogs to discuss what the law is in addition to what it ought to be. After all: if the law differs from what it ought to be, we need to know that both so we know how to protect ourselves and so we can take steps to change it. Otherwise, there is no magic mechanism to change bad laws with evil consequences into better law.”
I would agree with the intentions of these blogs and what you claim is their usefulness. My problem with most of them is that they are very predictable and that they do not stray far from the current intellectual thinking on issues. There is very little thinking out of the box about political systems – as I would assume comes from their experience and commitment to the current law and legal system.
lucia (Comment #117786)
July 18th, 2013 at 9:29 am
Lucia, I find that I can keep my phone protected under the tin foil hat I wear at all times. It works for me and I do not believe anybody notices.
RE: Carrick (Comment #117788)
July 18th, 2013 at 10:18 am
DeWitt:
No. A Faraday cage works by reflecting EM radiation. Grounding isn’t necessary for that. The conductive plastic bags in which electronics are shipped aren’t grounded. They’re not very good Faraday cages because the conductivity is low, but they’re good enough to keep static charges from getting inside.
If you have electronics in the interior (wires passing through), though, it does need to be grounded. Otherwise the external case case have a different potential than the grounded case for the electronics, and that can produce electronic noise.
###################################
This best explains the design requirements for a room full of electronics that need extensive shielding from RF energy and also require an earth ground for the faraday cage. A lot of this stuff was tested and developed in the days of Tesla and while many of us follow the guidelines in construction and engineering the theory behind the design is long forgotten.
ivp0, yeah basically if you have an interior metal case that has a different ground and the two enclosures aren’t electrically connected in any way…well, that’s a capacitor. It can store charge.
Kenneth
That may be the case at some blogs. But at Volokh, Orin discussed both current law and theories where monitoring would be illegal and evaluated what those say. This was in part prompted by Randy Barnett’s letter at the Wall Street Journal suggesting monitoring is illegal. (Orin is the 4th amendement specialists though.)
Putin interview. I think it’s recent. I’d say things do not look good for Snowden. I think the likelihood he will make it to Tegucigalpa are lower than I previously thought:
http://www.guardian.co.uk/world/video/2013/jul/17/vladimir-putin-edward-snowden-russia-us-video
lucia (Comment #117796)
July 18th, 2013 at 2:14 pm
“(Orin is the 4th amendement specialists though.)”
Which means that he has knowledge of how justices and the justice system generally considers the 4th amendment and the nuances of those considerations. If you are looking at the system as a whole and evaluating it against alternatives that information is not particularly compelling.
And compelling reminds me that when push comes to shove in our judicial system we have this compelling interest of the state for doing all sorts of mischief -even if the process is made to sound as though the government is made to jump through hoops to enforce an otherwise unconstitutional law.
“Once a court determines that strict scrutiny must be applied, it is presumed that the law or policy is unconstitutional. The government has the burden of proving that its challenged policy is constitutional. To withstand strict scrutiny, the government must show that its policy is necessary to achieve a compelling state interest. If this is proved, the state must then demonstrate that the legislation is narrowly tailored to achieve the intended result.”
http://legal-dictionary.thefreedictionary.com/Compelling+governmental+interest
Vladimir Putin would not, I suspect, have sympathy for someone who might expose government secrets as his instincts as a 16 year veteran of the KGB head would indicate. He would use Snowden to advance his own and Russia’s interests. I suspect almost all other nations in the world would provide asylum to further their interests and not as a statement against government secrecy. In fact I suspect that other nations would love to have the capabilities of doing what NSA does for the US.
I might criticize the US for its lack of freedoms but I have no illusions as to there being some safe haven out there in world were individual freedoms are totally respected.
Re: Carrick (Jul 18 12:03),
Speaking of grounding, I remember trying to chase down hum in my old stereo system (Heathkit vacuum tube). Sometimes you had to not ground one end of a shielded cable and reverse the non-polarized AC power cord. Modern audio electronics don’t seem to have this problem.
If one believed the sales literature, one could spend a small fortune on cables. I’ve seen testimonials that claim large differences in audio and video quality by changing brands of HDMI cables. I don’t believe them.
Re: lucia (Jul 18 09:29),
The problem is the interface between the foil and the pan. In the ad for the aluminum faraday cage, they made the point that all joints were welded. Aluminum oxide is a very good insulator, as many found to their dismay when their houses burned down because aluminum was used for a while to wire houses and the mechanical connections eventually oxidized and got very hot under load.
Dewitt, if you were able to get the hum out of Heathkit hi-fi amplifiers you were a better man than I. I gave up and went to Dynakits which didn’t hum although their designs were similar.
a bit of a stray current here, what?
Kenneth
I suspect all three countries (Nicaragua, Ecuador and Bolivia) who have offered asylum are doing it for their own interests.
I agree that Putin would use Snowden for his interests if that was a possibility. But I think Putin is having a difficult time finding something about Snowden that is in Putin’s interest. Meanwhile, I think on the one hand it sticks in Putin’s craw to just hand him over, but on the other hand… Snowden is mostly just a danged inconvenience for Putin. Putin and Obama had been moving forward planning negotiations, meetings etc. Then, out of the blue, Snowden drops into Moscow? Nothing about this is welcomed by Putin.
I think Putin is very not-happy that Snowden landed in Moscow. Putin has described him as an unwanted Christmas present. What Putin has been wanting more than anything is for Snowden to figure out how to leave.
And yes, as former KGB, it’s unlikely that Putin admires Snowden’s leaking.
“The thing you need to be aware of with application of any constitutional provision is that clear precedents generally do not exist for behaviors that were previously impossible to implement.”
lucia, you (or more precisely, the Volokh guys) are wading and wallowing in techno-legalese jargon to avoid confronting the simple fact that the US govt is snooping on its citizens. The law is an expression of human aspiration for liberty and upliftment and not the other way around. I.e., liberty is not an outcome of the legal process, nor contingent upon the minutiae of different laws.
Shub–
This isn’t ‘techno-legalese jargon’ — or at least, I have no idea what you think that is supposed to mean. You may not like the fact that the courts have not already ruled on the government’s snooping, but they haven’t. Or you may somehow think something can be “illegal” even if courts don’t haven’t ruled it’s illegal. But your not liking the fact doesn’t change it. If you think something is “illegal” merely because you decree it, you are mistaken. Whether something is “illegal” is a matter of law. It is not purely philosophical.
Also, the discussion here– and that there at VC– doesn’t avoid confronting the fact that the US gov’t is snooping on its citizens. The latter is totally acknowledged– we (and they) wouldn’t be discussing the legality of the snooping if we were not confronting the fact that it’s happening. So it’s ridiculous to suggest the motive for any ‘techno-legalese jargon’ is to avoid confronting the fact that the government is snooping.
Oh? Please explain how you think we are going to get our government to stop snooping if it’s not through application of laws — even if you the application of laws is somehow “minutiae”. Are you proposing revolution? (I would suggest that the outcome of any such thing would likely be increased snooping. Plus all sorts of other not-good things.) Are you proposing just discussing “principles” which are never to be condified or ruled on in courts but which somehow get applied? Because I’m rather mystified about how we could maximize liberty would ensue without any laws or without courts applying the laws to specific cases.
As for the bit you quoted: I am simply pointing out the fact that if a behavior was previously absolutely impossible, clear precedents about how various laws or amendments apply don’t exist. This is a simple fact. The consequence is that those arguing about what the law says don’t have access to rulings that apply to precisely the list of facts under consideration. No ruling can exist because due to previous limitations (in this case technological) the type of behavior the administration is indulging is was impossible. And our courts don’t bother making rulings about the legality of things that have never happened — and even more importantly– are thought impossible.
DeWitt,
“But since room temperature superconductors aren’t available yet, you can only attenuate, not eliminate. The induced eddy current will show up at some reduced level on the other side of any conductor with finite resistance.”
Yes, but I guess the depth of the induced eddy current is the key. If the metal thickness is not greater than the expected depth of the eddy current, then there will remain some transmission (though attenuated). According to Wikipedia, the eddy current depth is given by this equation: http://upload.wikimedia.org/math/f/d/7/fd7da721fa6562ef433eedc91d237f56.png Where f is the frequency in Hz, mu is the magnetic susceptibility, and rho is the electrical conductivity. It is the induced current which “re-radiates/reflects” the incident EM wave.
.
If I have done my math correctly, then for aluminum metal, the eddy current depth is ~2.84 X 10^(-4) cm (2.84 microns) at the 850 MHz cell phone band but only 3.53 X 10^(-7) cm (0.00353 micron) in the visible region (less than 35 atoms thick). So in all likelihood, aluminized plastic film that is reflective in the visible – where it is designed to be reflective – has far too little metal thickness to reflect effectively in the 850 MHz cell phone band. Completely sealed household aluminum foil (>25 microns thick) ought to block ~100% in the 850 MHz band. Getting a complete seal may be difficult.
SteveF==
That’s might be especially true of the foil I had at hand.
Lucia,
This web site: https://www.usaemergencysupply.com/emergency_supplies/mylar_food_storage_bags.htm
offers inexpensive Mylar bags which are two layers of mylar laminated with an aluminum foil layer of ~10 microns (should attenuate reasonably pretty well at 850 MHz), and have a zip-lock type seal along one end. Best of all, the small bags are inexpensive! 😉
Re: SteveF (Jul 18 17:41),
I believe that penetration depth is where the the intensity is reduced to 1/e that at the surface. So to get a 35 db reduction, which is about the leakage from a microwave oven door, you need ~8 times that depth or ~23 μm. And the covering must be continuous. Any contact resistance will be a potential leak. I don’t believe a zip-lock closure suffices in that regard.
There’s an interesting, to me, fantasy series, The Chronicles of Elantra by Michelle Sagara. The book titles all start with Cast In…. One of the races in the book are telepathic to an extreme. There is no such thing as privacy for them. In fact, the worst thing that can happen to one of them is to become, as it were, deaf.
Even for us, privacy is something of an illusion. Bluetooth, for example, is relatively trivial to crack. Which means someone with a directional antenna can listen to your cellphone conversation from quite a distance if you use a Bluetooth headset. Of course, it’s often hard not to listen to half the conversation without technology. Cloning a phone as done on the TV series Person of Interest isn’t as easy as it’s made out to be, but it’s not impossible.
The problem with Snowden is not so much the revelation of NSA snooping, it’s what else was on his drive that is now available to the Russians for sure and who knows who else. The snooping revelations look entirely too much like sleight of hand to distract from the transfer of really damaging information.
DeWitt,
You may be right about the 1/e factor for the eddy current depth. A 10-micron thick aluminum layer would not be perfect, but sure would cause a large (~1/e^(-3.7)) reduction in signal intensity. Maybe two bags, one inside the other, and with the zip-locks at opposite ends, would eliminate almost all signal transfer in or out. I also suspect that having an absorbing material inside the same closed structure would help to eliminate leakage by attenuating reflected energy (converting to heat). Some of this stuff: http://masttechnologies.com/mf2-lossy-foam/ would probably help reduce leakage a lot.
Phone in microwave oven: didn’t ring.
Phone in sealed aluminum foil packet (ends folded over on themselves several times): didn’t ring.
Phone in aluminum foil,not sealed: rang.
Phone in static shield bag end folded over several times: rang.
Folding and unfolding an Al foil packet would be a PITA.
DeWitt Payne (Comment #117810)
July 18th, 2013 at 8:00 pm
“Even for us, privacy is something of an illusion.”
Privacy and unwarranted searches by government can be two very different things. We give private entities private information in order to conduct efficient business. Governments attaining unwarranted information can be used by an agency that has a monopoly on the use of coercive force. I would hope we would not rationalize unwarranted or under warranted searches by government based how much information is used in private conduct of business or that private parties can illegally eavesdrop on conversations.
I know shortly after the NSA secret operations were revealed to the public the cable networks started talking about the information available to private concerns with Fox right up there leading the pack. If no distinctions are made there we are willingly giving up our individual rights.
We might want to have a conversation about why we need all this secret information and whether we as a nation might be better off minding our own business. Interesting that part of the damages of the revelations about the NSA activities is that we spy on our allies and that those allies now have to acknowledge it.
Re: Kenneth Fritsch (Jul 19 07:43),
Now there’s a tempest in a teapot. Every government that can spies on every other government and always has. I’m reminded of Claude Rains’ lines in Casablanca as he is being handed his winnings at the casino:
DeWitt Payne (Comment #117816)
July 19th, 2013 at 8:23 am
The more subtle point I was making was that we rationalize spying and secret courts because we say we need to know what are enemies are doing and then we spy on our allies in the process. The easy next step is spying on friendly citizens.
Or we could perhaps just roundup the usual suspects.
Re: Kenneth Fritsch (Jul 19 11:23),
We gather intelligence, spying has such nasty semantic connotations, about our allies as well as our enemies because allies don’t always agree on the same course of action even if they appear to do so in public. And who is to say that our allies will always be allies. In WWI, one of the first actions taken by Britain was to cut the trans-Atlantic communication cables connecting the US and Germany.
DeWitt Payne (Comment #117821)
July 19th, 2013 at 12:08 pm
“And who is to say that our allies will always be allies.”
And who is to say that our innocent civilians will always be innocent and not criminals.
I think we rationalize our spying and government secrecy based on either being at war or going to war. It is in that environment that we seem to allow the government to do things we might otherwise oppose and proponents of bigger government win.
It appears on important constitutional matters, the U.S. has the best government money can buy:
http://www.wired.com/threatlevel/2013/07/money-nsa-vote/?mbid=social10181434
“The numbers tell the story — in votes and dollars. On Wednesday, the house voted 217 to 205 not to rein in the NSA’s phone-spying dragnet. It turns out that those 217 “no†voters received twice as much campaign financing from the defense and intelligence industry as the 205 “yes†voters.”
Meanwhile:
Congress will hear testimony from critics of the National Security Agency’s surveillance practices for the first time since the whistleblower Edward Snowden’s explosive leaks were made public.
Democrat congressman Alan Grayson, who is leading a bipartisan group of congressman organising the hearing, told the Guardian it would serve to counter the “constant misleading information” from the intelligence community.
http://www.guardian.co.uk/world/2013/jul/26/nsa-surveillance-critics-testify-congress
Apparently Glenn Greenwald will be testifying via videolink, having been ‘forced into exile’.