[HN Gopher] Testing Phone-Sized Faraday Bags
___________________________________________________________________
Testing Phone-Sized Faraday Bags
Author : jor-el
Score : 319 points
Date : 2021-12-02 08:28 UTC (14 hours ago)
(HTM) web link (www.mattblaze.org)
(TXT) w3m dump (www.mattblaze.org)
| bflesch wrote:
| Perfect timing, I was just looking up this topic in the last
| week.
|
| But how come these are all US-exclusive. It seems both winners
| don't ship to EU :/
| intrasight wrote:
| I built something in college that needed UL testing for RF
| emissions, and visited a facility in Long Island with a TEMPEST
| room about the size of my house. Was very memorable.
|
| I also read an article this year by a guy that made his house
| radio-wave proof, because, he claimed, he was very sensitive to
| radio waves. It was WAY more involved than I would have guessed -
| for the same reasons discussed in this article and in this HN
| discussion. Nails and screws are a problem. Windows are a big
| problem. But still - how cool to be cut off from the onslaught of
| EM radiation.
| jimmySixDOF wrote:
| My understanding is that a Faraday Cage, of any size, relies on a
| proper grounding system to work at all so these boxes and rfid
| blocking pockets etc all seem to be tinfoil hats parading as
| space age metamaterials.
| formerly_proven wrote:
| > relies on a proper grounding system to work at all
|
| does not
| h2odragon wrote:
| Good RF ground is a _bitch_.
| dtgriscom wrote:
| Nope: RF shielding has nothing to do with having a ground
| reference.
| snowwrestler wrote:
| A faraday cage converts the energy in the radio waves it
| absorbs into heat.
|
| Eventually it will radiate the same amount of energy as the
| transmitter inside it, but in infrared wavelengths and without
| whatever modulation was carrying the signal.
| authed wrote:
| Apparently not: "Small Faraday cages with no conductors
| penetrating the shield do NOT need to be grounded."
| docflabby wrote:
| Tinfoil hat on - has anyone considered how suspicious that only
| the commercial products worked, maybe the post is just a very
| clever shill for those products?
| tablespoon wrote:
| > Tinfoil hat on - has anyone considered how suspicious that
| only the commercial products worked, maybe the post is just a
| very clever shill for those products?
|
| Not really, tinfoil actually worked, but it was apparently too
| difficult to get right:
|
| > In my experiments, I found I could sometimes achieve
| approximately 90 dB attenuation by carefully wrapping the
| generator in foil and double folding the seams on all sides,
| which is quite good (comparable to commercial pouches).
|
| This actually matches my experience with a GPS logger. It only
| had an on/off switch and I wanted to download the track from my
| trip without getting points from the download location at the
| end. IIRC, it was still able to get fixes even wrapped in tin
| foil.
| tomxor wrote:
| > "Wrap it in tin foil" is perhaps the most common advice [...]
| Unfortunately the results were extremely inconsistent [...] 90 dB
| attenuation in one test would produce only 50 dB the next time
| [...] You would have no way to tell whether you've managed to
| fold and seal it adequately well
|
| On the other hand, aluminium foil is incredibly commonly
| available, if not in a kitchen draw, it will be at the nearest
| shop. Although unreliable, the _potentially_ high attenuation the
| author shared is pretty good (we don't know his worst reading),
| better than all other improvised solutions tested, and similar to
| commercial products. I wonder if a more reliable construction
| method could be found.
|
| I'm not sure what movie scene scenario I'm envisioning, but in
| the case you needed a Faraday cage and don't constantly carry one
| around, perhaps simply taking an entire kitchen roll of foil and
| wrapping the device into a giant unsightly ball of it would be a
| reliable enough process for an "emergency" (if not pocket sized).
| i.e rather than trying to make a neatly folded minimal version,
| just resort to sheer number of layers of material - unless RF
| doesn't care and even 1000 layers with tiny gaps is no good?
|
| [edit] Similarly, I wonder how well (or poorly) common household
| appliances work as a Faraday cage, e.g a fridge, microwave-oven -
| From what the author described, it seems they would all have too
| many gaps, however they are also constructed from higher gauge
| metals... i'm particularly interested in a microwave-oven which
| is specifically designed to reflect and retain microwave
| frequency fields.
| tomkat0789 wrote:
| I'm not an expert on Faraday cages, would the effects stack if
| you wrapped your phone in aluminum foil, then put it in a
| cookie tin?
| willis936 wrote:
| Microwave-ovens definitely don't leak below 2.4 GHz. Any
| frequency above that is a non-issue for microwave-oven operator
| safety. It also wouldn't be an issue for any communication
| device transmitting below 2.4 GHz. If you want to shut down 5
| GHz communication then a microwave-oven would be leaky. 60 GHz:
| it shouldn't matter since it needs LoS anyway.
|
| Also, remember to ground your faraday cages.
| posix_me_less wrote:
| > ground your faraday cages.
|
| Why?
| willis936 wrote:
| Better performance. Faraday cages can act as reradiators at
| frequencies dependent on cage geometry.
| hobs wrote:
| I assume for the same reason you ground your home, building
| up charges is a great way for Bad Things to happen.
| posix_me_less wrote:
| Why would a phone pouch/box build up great charge? You
| don't ground your home because of charge buildup either -
| grounding is there to decrease the chance a thunderbolt
| will run through precious things, like house walls,
| people, electric wiring etc.
| oasisbob wrote:
| Grounding and bonding is done for many safety reasons.
| Reducing stray voltage is certainly one of them:
|
| https://www.mikeholt.com/technical-stray-voltage-
| newsletter-...
| hobs wrote:
| You absolutely want to ground your home due to charge
| buildup, I have seen the exploded appliances, no
| lightning required.
| formerly_proven wrote:
| The width of the area around microwave doors looks
| suspiciously close to lambda/4 for 2.4 GHz (~3 cm) on pretty
| much every microwave I've ever seen - I'd almost be surprised
| if that construction _isn 't_ tuned to reflect 2.4 GHz, which
| would make it a very leaky container at say 0.9/1.8 GHz.
| willis936 wrote:
| I think you should double-check the harmonics that would
| get passed relative to a quarter-wave mesh.
| jjoonathan wrote:
| Microwave ovens make for poor Faraday cages. The problem is
| that you only need 30-60dB to "keep the power in" while you
| probably want at least 100dB to "keep the signals out."
|
| You can test this: put your phone in the microwave and try to
| call it. Over the years I have had about a 75% success rate.
|
| Other household appliances tend to be even worse; any gaps in
| metallic seals effectively turn into slot antennas and let
| signals through. You need a conductive mesh gasket to stop
| this, and I generally don't see mesh gaskets on consumer
| appliances.
|
| Your "make an al-foil ball" strategy is what I would resort to
| in a pinch (I have some nice Anritsu shield boxes, but those
| are cheating). Quantity is a quality of its own. My only
| addition would be making sure that the gaps tend to not line
| up. You want to make it difficult for the "slot antennas"
| modeling the gaps in each layer to couple to each other.
| rocqua wrote:
| For the sake of keeping people from doing stupid things.
|
| DO NOT MICROWAVE YOUR PHONE.
|
| The test involves placing your phone in the microwave and
| closing the door without turning the microwave on. I'd unplug
| the microwave before trying this.
| teddyh wrote:
| "This is a man who has experienced The Public"
|
| -- https://www.reddit.com/r/tumblr/comments/jy8wzj/rinse_yo
| ur_e...
| IncRnd wrote:
| This article was a fun read, and it really highlights how we
| trust the words on the tin to be accurate and not mistaken
| marketing gibberish.
|
| However, the part about the cost ranging from $40 - $80 is simply
| not true. I know this, because I purchased for $20 yesterday a
| faraday box to hold my auto key fobs and my cell phone. [1] There
| are very many items for sale at this price point, fabric, pouches
| and boxes.
|
| [1] https://smile.amazon.com/s?k=faraday+box
| pro_zac wrote:
| Key fobs! Isn't there a scheme where thieves clone the signal
| from a key fob when the owner is asleep in their home and drive
| off with their car?
| IncRnd wrote:
| Here's hoping I get a good faraday box from Amazon!
| Tronno wrote:
| What's the use case for these products?
|
| Even if the radio is blocked, how does that stop a device from
| collecting data anyway, and exfiltrating it the moment it finds a
| network? Won't it look for a network the moment you take it out
| of the bag? And don't you _have_ to remove it from the bag to use
| it practically?
|
| Ultimately, if your device is compromised or untrustworthy to the
| extent that it has to be policed this way, is it not safer to
| just... get rid of it?
| jpl56 wrote:
| Please reduce the image size, they seem to be 3 Mb each. Some
| people (especially if their phone is in a pouch) won't be able to
| get to the interesting parts of your article!
| comeonseriously wrote:
| I think they could have done a better job with the aluminum foil.
| It looks rather not well done. He could have made a pouch and
| folded the sides over a few times.
|
| I made a pouch for my car's key fob with aluminum foil and metal
| tape. It isn't as pretty as the ones you can buy, but it wasn't
| $25 either and It has worked really well.
| aaroninsf wrote:
| I am happy to see EDEC performed well.
|
| Idle comment: we use their smaller keychain bags for car fobs,
| after hearing with dismay first- and second- hand accounts of
| relay attacks being used to steal or ransack cars in our
| neighborhood (94110). We now keep our fobs in them except in use.
| wolverine876 wrote:
| What is the use case for disabling wireless communication for
| your phone? How will you use it? How will anyone call you? If you
| don't want to use wireless functions, buy a tablet that lacks all
| the radio hardware.
| jagged-chisel wrote:
| Bad Guys can't follow you using the signal. That's about it.
| Sure, they can tail you, but that's Work. And they'll know
| where you are the moment you take it out, but hopefully they're
| too far away to act on it.
|
| All in all, if you NEED something like this, your opec had
| better include more than this.
| wolverine876 wrote:
| > Bad Guys can't follow you using the signal. That's about
| it. Sure, they can tail you, but that's Work. And they'll
| know where you are the moment you take it out, but hopefully
| they're too far away to act on it.
|
| Why have the phone if it's not connected to the network? It's
| a communication device. Just leave the phone home.
| SamuelAdams wrote:
| This is a super cool blog post. However I think it alludes to a
| much larger problem. For many products today, it's very difficult
| or impossible for most people to verify the product works.
|
| For a network switch, there are free and open source tools like
| iPerf to test and verify speeds are as advertised. For a faraday
| box, you have to go through all these steps (and knowledge
| learned) just to be able to test these. What about for vitamins,
| or pet food, or any other "durable" products that are supposed to
| last for X years?
|
| In an age of snake oil salesmen, paid for reviewers, and
| fraudulent products on Amazon, there is a real opportunity for
| creating systems that enable individuals to verify products do
| what the sellers claim they do.
| wolverine876 wrote:
| > What about for vitamins, or pet food, or any other "durable"
| products that are supposed to last for X years?
|
| We could, as a society, make rules that prohibit these things
| and create organizations with the expertise and power to
| enforce those rules. We are hardly helpless, but the political
| trend is to forgo and even decry that power, do nothing, and
| then whine about how helpless we are.
| lvs wrote:
| It's called consumer protection, and it's weaker in the US
| than many other advanced countries.
| readams wrote:
| This problem was most famously studied by Akerlof in The Market
| For Lemons. The prediction is that such a market will be
| overrun with low quality lemons.
|
| https://en.wikipedia.org/wiki/The_Market_for_Lemons
| RandallBrown wrote:
| An easy solution would be putting your phone in the bag and
| have someone else call it.
|
| The post does mention something similar near the bottom where
| they suggest putting an AirTag in the bag and seeing if your
| phone can find it.
| dannyw wrote:
| It's supposed to be called the Federal Trade Commission.
| goldenkey wrote:
| I suppose the FDA is also supposed to make sure our food
| isn't leaded?
|
| These agencies seem to test one vector while ignoring
| everything else. I don't trust them.
|
| https://www.consumerreports.org/food-safety/your-herbs-
| and-s...
| adolph wrote:
| > For many products today, it's very difficult or impossible
| for most people to verify the product works.
|
| _Some people, when confronted with a problem, think "I know,
| I'll use regular expressions." Now they have two problems._ -
| Jamie Zawinski via Coding Horror [0]
|
| To your point, maybe Zawinski's aphorism is broader than
| regexp.
|
| The quote investigation [1] linked from CH is well worth
| reading.
|
| 0. https://blog.codinghorror.com/regular-expressions-now-you-
| ha...
|
| 1. http://regex.info/blog/2006-09-15/247
| sdoering wrote:
| I agree that the free market is easily gamed and therefore I
| really am glad to be living in a country with relatively strong
| consumer protection laws.
|
| I buy online, I can return within two weeks no question asked.
|
| It breaks within two years - I return it. Either I get a
| repaired one or a new one or my money back.
|
| There are few exceptions but mostly it makes shopping quite
| secure.
|
| Yes. There are bad actors. Yes people get ripped off by shady
| online stores. But if using trusted shop, PayPal or one of the
| known big shopping brands the experience is mostly good.
| wilkommen wrote:
| What country do you live in?
| cevn wrote:
| Sounds like something in EU to me.
| fpoling wrote:
| Norway has similar 14 day return right for things ordered
| online. It is originated in eighties when the phone or
| postal orders became popular. Basically if you do not have
| a chance to examine the thing one is getting like in a
| physical shop, the seller must accept returns within 14
| days. This cannot be restricted to unopened or unused
| things.
| pbhjpbhj wrote:
| 2 years is minimum default warranty by law in EU.
|
| In the UK we have a warranty period with no particular
| limit, undergirded by the EU 2 year default, through the
| Consumer Rights Act -- basically it's founded on how long
| products would be reasonably expected to last, a fridge
| should last a decade, a cheap toy arguably far less.
|
| But, I've had a problem with this that I think it's a
| useful example: Steam sold me a defective game, I tried to
| play it but the bugs ultimately made it impossible to enjoy
| (the purpose of entertainment!). Under the CRA digital
| goods are explicitly included in the ability to return when
| defective; but Steam/Valve decided their rules on "play"
| time trumped UK law. PayPal provided a refund (tiny amount
| of money) in accordance with their terms, but now Steam
| have taken revenge (the employee time spent on the issue
| certainly cost more than the original purchase),
| threatening to close, and then simply limiting my account.
| That should be illegal IMO, but I don't know if it is. I'm
| not going to pursue them at this point.
|
| Imagine if a fast-food outlet said "if you complain about
| your food we'll ban you from buying from us", that would
| have a perverse effect on consumers and reduce the ability
| to push back against instances of low quality food. Sure,
| you can boycott them but that seems worse for everyone.
|
| TL;DR at least in the digital domain, even with strong
| consumer protections companies can work around the law.
| throw10920 wrote:
| I'd like to describe a complementary problem to yours - that
| it's very difficult or impossible to find out others'
| experiences with a product's quality, durability, and
| performance. That is - the complement to the problem of "it's
| hard to determine if some products work" is "it's hard to find
| other users' experiences with the product".
|
| Amazon reviews are completely worthless, but very few other
| platforms have anywhere close to the same number of reviews on
| them. Most platforms have no verification of purchase for
| reviews. It's hard to determine information like "does this
| device require a cloud login? for which functionality? are
| there ads?" that isn't explicitly supplied by the manufacturer
| (or hidden by them). Negative reviews about product breaking
| quickly aren't very useful because people whose products work
| for a long time leave reviews at a lower rate. Google is almost
| useless for finding out information like this because of how
| SEO-gamed everything is, and the ol' "site:reddit.com" trick
| will only work for a while longer until these fraudsters create
| enough fake reviews on Reddit that it also succumbs (which is
| already beginning).
|
| (rant "...and this problem will likely won't be solved anytime
| soon, because consumers don't _care_ about these things. That
| 's the reason that we're in this situation - consumer apathy.
| When was the last time you heard a non-tech-savvy relative say
| something along the lines of "Wow, this phone didn't last very
| long. Is there a place where I can add that data point so that
| other people will be more informed before they purchase one?"
| Users don't care about performance, privacy, or durability -
| they just want to watch Netflix and pay the lowest sticker
| price they can (regardless of annual cost of ownership). You
| see people self-organizing around things like video games or
| paintball or book clubs or whatever all the time - why won't
| they put even a fraction of that effort into ensuring that they
| buy a good car?")
| Tijdreiziger wrote:
| Amazon and Coolblue reviews have been decent for me. With
| Amazon, the nice thing is that even if there aren't any
| reviews on your local Amazon, it will show reviews from other
| countries' Amazons with the option to translate. Combine that
| with professional review sites like Rtings or The Wirecutter
| and you can usually get a decent idea.
| thatguy0900 wrote:
| Maybe products have just reached a point of being overall
| just cheap enough and just good enough that consumers largely
| don't need to care about reviews? You talk about effort to
| buy a good car, maybe the average car is just good enough
| now. I wonder what percentage of younger people have bought
| an actual lemon that would cause them to be cautious.
| newaccount74 wrote:
| > because consumers don't care about these things
|
| I think that's not the issue. Consumers DO care about durable
| products, and consumers DO share their experience. Consumers
| talk to others about stuff they like all the time, and they
| also complain to others when stuff doesn't work. Consumers
| also spend a lot of time online researching products.
|
| Amazon Reviews were amazing in the beginning, because so many
| customers shared their honest experience.
|
| The problem is that as soon as there is a popular place where
| people go to read reviews, companies realise they can make a
| lot of money if they post fraudulent reviews (or send free
| samples to folks who write positive reviews). Products with
| good reviews make lots of money, so companies are going to
| put a lot of effort into getting good reviews.
|
| On the other hand, consumers trying to share their honest
| experience don't have anything to gain from doing so, so they
| are not going to put as much effort into sharing their
| experience.
| theshrike79 wrote:
| Linus Tech Tips is attempting something in this field:
| https://www.youtube.com/watch?v=pt3-6BsWlPk
|
| tl;dw They're building a setup where they can test a bunch of
| computer equipment with standardised tests (built by them) in a
| standardised environment (also built by themselves).
| gangstead wrote:
| Sounds like what Consumer Reports does across various fields.
| mrguyorama wrote:
| Gamer's Nexus, also on youtube, has done something very
| similar and designed a bunch of "Standardized" tests for
| their benchmarks of computer systems and hardware
| fsflover wrote:
| I prefer smartphones with kill switches, Librem 5 and Pinephone.
| 323 wrote:
| But you need to trust that they are actually working, and that
| the device was not intercepted and modified en route.
| fsflover wrote:
| They have the schematics [0,1] for these devices and even
| X-rays [1] for Librem 5. Also, anti-interdiction services for
| the latter [2].
|
| [0] https://wiki.pine64.org/index.php/PinePhone#PinePhone_boa
| rd_...
|
| [1] https://source.puri.sm/Librem5/community-
| wiki/-/wikis/Freque...
|
| [2] https://puri.sm/posts/anti-interdiction-services/
| pseudolus wrote:
| Bit of an aside but the ineffectiveness of tin foil hats to
| prevent government intrusion into our minds has been known for
| some time :)
|
| http://web.archive.org/web/20100708230258/http://people.csai...
| tzs wrote:
| I've lately started seeing claims on some of the forums that
| embrace things like vaccines contain 5G mind control chips
| claiming that lead effectively blocks government mind control
| and that is the real reason lead paint was banned, and that it
| is not actually harmful.
| Arrath wrote:
| Oh for the love of god
| parkertomatoes wrote:
| I was hoping they would test chip bags, because it was a plot
| device in the most recent Terminator movie.
|
| After searching, I found that Kaspersky has a blog post on the
| topic: https://usa.kaspersky.com/blog/terminator-dark-fate-
| chips/18...
|
| It surprised me that chip bags were more effective in their test
| than cookie tins, but only when they double-bagged it
| alliao wrote:
| truck drivers used them too to avoid tracking from their
| employer
|
| https://arstechnica.com/information-technology/2017/11/austr...
| teddyh wrote:
| Also used in the, IMHO, underappreciated film _Enemy of the
| State_ (1998).
| bborud wrote:
| At my former job we had a rather large faraday cage for testing
| telco equipment. Two things surprised me: 1) It is more fiddly to
| ensure a room-sized faraday cage doesn't leak RF than I thought.
| It is really easy to make mistakes that compromises experiments.
| 2) There was a bath-towel sized piece of cloth that came with one
| of the expensive Rohde & Schwarz instruments that was
| astonishingly effective at blocking signal.
|
| So I mainly used the room because that's where the magic blanket
| was - which was easier to use than ensuring the room was set up
| correctly.
| op00to wrote:
| I see one of the founders (Ulrich Rhode) of Rhode and Schwarz
| on amateur radio some times, and I always ask for test
| equipment and he always says no.
| kortilla wrote:
| Maybe stop asking then?
| shapefrog wrote:
| I see you are from <insert whatever company you are at is>,
| can you please send me a lifetime supply of whatever you make
| / have / sell please?
| op00to wrote:
| Hey, when my customers ask they are free to have a lifetime
| supply of our product! It's free to anyone!
| Luc wrote:
| That's very cool, he's basically test equipment royalty. But
| he's the son of one of the founders - Rhode & Schwarz was
| founded in the 1930's.
| op00to wrote:
| It's good natured ribbing usually exchanged over QSL cards.
| I didn't know he was the son! Ulrich never misses a QSL
| card for me. Cool dude!
| relaxing wrote:
| I once tried to acquire a RS PR100 like the one used in the
| test here. Turns out they cost more than a fancy car!
| op00to wrote:
| I wonder how much more capable they are than the cheap crap
| I can afford.
| relaxing wrote:
| A lot! An Ettus USRP + GNURadio could get you part of the
| way, but you then you don't get the nice handheld form
| factor and ruggedized chassis.
| pdkl95 wrote:
| I really like Snowden's recommended Faraday cage for phones or
| other devices of similar size: two drink-shaker cups[1].
|
| Drink shakers are cheap and widely available. The average hotel
| room in any medium/large hotel chain probably includes a shaker
| as a standard item as part of the minibar. The simple two-cup
| style (as seen in [1]) is preferred over the fancier "strainer
| top" style because you can press the two cups together; this
| should cause the inner cup to slightly cut into and/or deform the
| outer cup along the circle where they join together. The seal
| between the cups should work sort of like the knife-edge seals
| used in vacuum chambers.
|
| A metal box or conductive bag is only a Faraday cage if it is
| fully closed/sealed. Any imperfection in the seal or hole[2]
| might allow the radio signal to leak out. Most improvised items
| (freezer, random metal box, etc) have poor seals. Making a high
| quality cage that actually block a modern phone can be done
| without much trouble, but the drink shaker method is the only
| method I know of that will do the job using widely available
| (free) or very cheap ($10-ish?) parts.
|
| [1]
| https://ae01.alicdn.com/kf/HLB1yRyhXZTxK1Rjy0Fgq6yovpXaZ/Win...
|
| [2] Holes of sufficient size. How big are the waves you are
| trying to block?
| kurthr wrote:
| If you're interested in simple cages similar in effectiveness
| to the EDEC Window Pouch (they drop off above 3GHz)... try a
| Microwave Oven. They are highly available, reasonably
| convenient and well designed, with pretty good quality control.
| You can even still see your phone inside has zero bars. I do,
| however, recommend unplugging the microwave (or even cutting
| the power cord) as a fire would likely result from cooking your
| hardware.
|
| To answer [2] How big are the waves you're trying to block? -
| it's actually crack length not width that usually determines
| the effective re-radiating antenna length. They can be very
| narrow, but a long (a few cm) crack will allow one polarization
| through almost completely.
|
| I've run this test with a GSM base station and confirmed the
| effectiveness. If you want to test communication with a device
| to a base station, but have many other local antennas
| interfering and want to fit many devices inside... it's a
| decent choice. The alternatives are less convenient and usually
| thousands of dollars to construct.
| sumtechguy wrote:
| At one company I worked at we had an 'out of coverage bucket'.
| It was a zinc plated steel bucket. Worked almost every time.
| Some dude had found at an arts and craft store a _very_ small
| version of the same thing. It fit over phones perfectly.
| Basically put device on ground. Put bucket over it. If you had
| any gaps or any cables hanging out it was sort of iffy and you
| would get coverage sometimes.
| 14 wrote:
| I think the issue is then you have to wait until you are
| already inside the hotel to use those shakers, which as others
| have said don't actually exist in most hotels, and at that
| point you have been tracked to your exact location. Then it
| would be trivial to surveil you with other methods without
| needing your phone.
| JacobThreeThree wrote:
| Pretty sure Google uses dead reckoning geolocation tracking
| when no signal is available. So as long as your phone is
| outside of the bag at some point, you're being tracked even
| when the phone is in the bag, and Google can correct any
| errors in their dead reckoning calculations once a signal is
| found.
| BenjiWiebe wrote:
| It's possible, but I'd be surprised. Dead reckoning is
| _terribly_ inaccurate. To get briefly acceptable accuracy,
| you need extremely precise sensors that you are reading
| very very quickly (which would make battery life plummet).
| MR4D wrote:
| Now would be a great time to sell a ton of mints that just
| happens to fit an iPhone max with a case inside.
|
| "Security Mints - sweet & secure".
|
| Maybe a kickstarter?
| ncmncm wrote:
| It is hard to believe this would perform better than a
| Lazzaroni tin.
|
| And I don't recall ever finding one of these things in a hotel
| room, even in Europe.
| ejolto wrote:
| Depends what the tin and shaker are made of. The tin is
| probably made of aluminum which has a higher skin depth than
| stainless steel, which I assume the shaker cups are made of.
| A Faraday cage of continuous surface needs walls that are
| thicker than the skin depth of the material the cage is made
| of. Since the skin depth of stainless steel is lower, the
| cage wall thickness can be lower while still creating an
| effective Faraday cage compared to an aluminum cage.
|
| Ref skin depth of different materials at different EM frequen
| cies:https://upload.wikimedia.org/wikipedia/commons/f/f3/Skin
| _dep...
| yosito wrote:
| Reminds me of a joke my dad used to tell:
|
| Dad: What's five plus five?
|
| yosito: Ten!
|
| D: How many fingers do you have?
|
| y: Ten!
|
| D: What's an aluminum can made out of?
|
| y: Tin!
|
| D: Wrong! Aluminum!
| amluto wrote:
| The tin is painted, and paint is nonconductive. A very thin
| long slit in an otherwise conductive surface or mesh can be
| extremely leaky.
| geewee wrote:
| I'm from Europe and I've never seen one either.
| ghaff wrote:
| I imagine I've seen them now and then but they're hardly
| common. I'm grateful when I get real glassware.
| causi wrote:
| What's the physics behind being able to make a container light-
| tight with a couple of right angle corners yet radio waves seem
| to leak out like water?
| foobarian wrote:
| Does the right-angle corner trick still work if the container
| surfaces are made of mirrors?
| newaccount74 wrote:
| There are two important differences between light and radio
| waves:
|
| Difference 1 is the wavelength. Light has a wavelengths of
| 400-700nm, whereas radio waves used by phones have
| wavelengths in the mm and cm range.
|
| If structures are of similar size to the wavelength, then
| waves can "bend around" obstacles. This effect is called
| diffraction and can be observed with sound waves,
| electromagnetic waves, water waves, etc.
|
| Difference 2 is the photon energy / frequency. How well
| radiation is absorbed depends on the photon energy. There are
| lots of molecules that absorb visible light very well, so
| it's easy to make surfaces that absorb light. But there are
| few things that absorb radio waves as well, so it's hard to
| make things that neither reflect nor transmit radio waves.
| hammock wrote:
| A couple of right angles not really make it light tight
| either.
|
| I remember going caving and we would have to go 100m or more
| through many different turns before we all turned our lamps
| off and truly experienced perfect dark.
| devb wrote:
| Are you familiar with daylight tanks for film processing?
| They work as advertised using right angles.
| pdkl95 wrote:
| The last time I used a daylight tank was in the mid '90s
| so maybe newer models are different, but I believe they
| are made out of black/dark plastic? Several right angle
| turns of black plastic provides multiple opportunities
| for a visible-light photon to be absorbed into a black
| body where it should be re-radiated as infrared (heat).
|
| A hole/leak in the metal wall of a Faraday cage is going
| to be a lot more reflective and can easily act like a
| crude _waveguide_ [1].
|
| [1] https://en.wikipedia.org/wiki/Waveguide_%28radio_freq
| uency%2...
| newaccount74 wrote:
| There's an old man made cave near me that consists of two
| small connected chambers, and once you are in the second
| chamber it is pitch black.
| 2rsf wrote:
| Radio waves (well, light and radio are the same thing just
| with different wavelength) are bounced from conductive
| materials, light is absorbed
| relaxing wrote:
| Light bounces too. As you said, it's the same thing.
| alecdibble wrote:
| How much EM radiation bounces and how much it gets
| absorbed is highly variable depending on the material
| and, most importantly, the frequency of the EM radiation.
| A great example in this article is the faraday bag that
| was visibly transparent but blocked the EM radiation in
| the 1-6gHz range. The metal tin was basically the
| opposite, it blocked visible radiation very effectively
| but not radiation in the radio frequency range.
| rocqua wrote:
| Also, 20-30 Db of attenuation for light is already quite a
| lot. Whilst for a radio signal it is still very conceivable
| that 30Db of attenuation still allows for a signal to be
| received.
|
| Our eyes simply aren't very sensitive instruments. And the
| visible part of the spectrum is uncharacteristically full of
| 'noise', so it makes some sense that our eyes don't need to
| detect any signals that are too far below the noise-floor.
|
| That makes me wonder. How much 'darker' is any given bit of
| radio spectrum as compared to the visual spectrum earth at
| night.
| elbasti wrote:
| > our eyes aren't very sensitive instruments
|
| I take umbrage with that statement! Our eyes are
| _exquisitely_ sensitive, and most importantly, have
| staggering dynamic range.
|
| Our eyes are capable of perceiving a single photon [1],
| albeit noisily (I've been lucky enough to have performed
| this experiment myself!).
|
| But the greatest thing about our eyes is the dynamic range:
| the difference in brightness between a moonless, starry
| night (which we are perfectly capable of navigating by
| eyesight) and a bright sunny day is _nine orders of
| magnitude_. A bright day is a billion times brighter!
|
| Show me an RF receiver or light camera with that dynamic
| range!
|
| The one place our eyes are limited is in frequency range.
|
| [1] https://www.nature.com/articles/ncomms12172
| rocqua wrote:
| I knew the dynamic range was large. I did not know about
| the sensitivity! That is quite impressive.
|
| The magnitude of the dynamic range is even more
| impressive if converted to 'stops' from photography,
| yielding about 30 stops (1 stop halves the light).
| Whereas a really good camera will do about 15 stops.
| Though I suppose that the camera gets 15 stops in a
| single 'scene'. Whilst the 30 stop figure for the human
| eye does not hold up if half your vision is taken up by
| daylight and the other half by a night sky. For a single
| 'scene' I think it becomes hard to define the dynamic
| range of a human eye though.
| nabla9 wrote:
| Microwave wavelength lower than visible light. It interacts
| with atoms differently by interacting with magnetic fields in
| atoms more.
|
| There is:
|
| - lines-of-sight propagation in free space,
|
| - reflect from the surfaces like light (spectacular
| reflection)
|
| - microwaves can be channeled trough tubes (think sound
| waves). If you fold a conductive material like tin foil
| multiple times, it can still work as a wave guide and escape.
| adolph wrote:
| > The average hotel room in any medium/large hotel chain
| probably includes a shaker as a standard item as part of the
| minibar.
|
| Maybe the hotels you stay in, Bond, James Bond.
| pdkl95 wrote:
| I admit the vast majority of my experience with hotels
| consists of a single repeated data point: the staff[1]
| suite(s) we shared in the Hilton attached to the SJ
| convention center. They always had glasses/shaker/etc. You
| could probably ask for a shaker from roomservice or the hotel
| bar, if necessary.
|
| [1] If you registered for FanimeCon 2000-2011, the weird
| software you had to use was my fault...
| adolph wrote:
| She's not an average ship, Jim!
| speedgoose wrote:
| Hilton is a tiny bit more fancy than the average.
| GordonS wrote:
| > The average hotel room in any medium/large hotel chain
| probably includes a shaker as a standard item as part of the
| minibar
|
| I've stayed in dozens of hotels all over the world, and never
| once have I seen a cocktail shaker in the minibar?!
| ghshephard wrote:
| I've stayed in over a hundred, frequently in suites
| (upgrades), often at 4* hotels, in 22 countries (Full set of
| brands - Marriot, Hyatt, JW, etc...) Ice Buckets are pretty
| common - but I have never once seen a drink shaker in a room
| mini-bar.
| srcreigh wrote:
| The Fairmont Royal York in Toronto has shaker cups. It is
| 5-star though.
| scottdupoy wrote:
| > While the cookie tin performed much better than the mylar bags,
| and could provide a modicum of useful attenuation under some
| circumstances, it was not sufficient to provide meaningful
| assurance of signal isolation at any frequency. However, it was
| unique among the containers tested in providing tasty snacks
| during measurements
|
| Back in the day working for Symbian I used to regularly have to
| run a load of automated Bluetooth tests. Unfortunately there were
| 200+ engineers in the close vicinity of my test setup and they
| all had smartphones and all had Bluetooth turned on, causing
| loads of the test to timeout. We were very pleased with ourselves
| when we thought of using a biscuit tin as a Faraday cage to try
| and improve things. Didn't work as well as we hoped, but got the
| tests running within their timeouts. I always thought it'd be
| interesting to try using an old microwave.
|
| Best thing was that we got to eat all the biscuits first :)
| kingcharles wrote:
| When I was in jail I had a cellie who imported drugs from
| China. They were always shipped inside defunct microwave ovens.
| I wondered if it was just because it looked like a harmless
| kitchen appliance or because the microwave provided shielding
| from an x-ray scan?
| habi wrote:
| This really depends on the X-ray machine, a powerful x-ray
| source might easily penetrate a small appliance.
|
| A faraday cage/bag does not protect x-ray since it 'only'
| blocks electromagnetic fields.
|
| So I guess in the case you mention it's more hiding in the
| insulation/empty space of an appliance.
| BenjiWiebe wrote:
| X-rays _are_ electromagnetic radiation.
| duskwuff wrote:
| Technically speaking, yes. But they're way off on the
| other side of the EM spectrum, giving them dramatically
| different properties. You can shield against radio with a
| shell of any conductive material -- even a wire mesh for
| longer wavelengths -- but X-rays are only absorbed by
| high-atomic-weight atoms, like lead.
| habi wrote:
| Of course the are, but - if I'm correct - they don't
| produce an electromagnetic field. And are _not_ shielded
| by a bit of mesh wire (I work with desktop microCT
| machines...).
| redleader55 wrote:
| The simplest test you can make to verify that the microwave
| oven & biscuit tin can are good Faraday cages is to put your
| phone in one and try to call it - every time I did that in the
| past they failed to function as a Faraday cage.
|
| Edit: clarification.
| dzdt wrote:
| The Faraday cage failed (the phone rang?) or the phone failed
| to ring (Faraday cage succeeded)?
| redleader55 wrote:
| Clarified the text of my original comment.
| OJFord wrote:
| That's an easy way to verify failure (phone rings) but not
| success - unless the only thing you care about blocking is
| phone calls I suppose.
| jmnicolas wrote:
| Did you wrap your phone with something non conducting so that
| it doesn't touch the tin or microwave?
|
| It works for me with a cookie tin, the phone is wrapped in a
| towel.
| aurizon wrote:
| Biscuit tins and aluminium foil have layers of insulation on
| them, the varnish of the tin and the Al2O3 oxide layer for the
| foil. It is true that the gap in each case is small, but when
| you look for 10 orders of magnitude in attenuation - a little
| leakage goes a long way. Silver has the unusual property in
| that both the metal and it's oxide are both conductors = true
| silver foil made of thin metallic silver will make a good wrap
| around Faraday bag. Even better would be true gold metal foil -
| note they often use gold plated shields in space uses, even
| though gold foil is like fly paper in space = contact welds
| readily, much more so than most other metals (many of which
| have also contact weld problems that have to be mitigated).
| Those Ramsey boxes are excellent, far better than many
| costlier, but crappier boxes, obviously made by someone who
| knows an ohm from a volt...
| formerly_proven wrote:
| I think the biggest issue with cookie tin cans is that they
| usually don't close all the way around, because the lid or
| the box is always slightly oval and not round (they always
| "stick" just in two or three spots when opening), so it looks
| like there's a small gap around half the circumference long -
| far bigger than the wavelengths in question.
|
| Square tin can works better because those seem to usually
| scratch on the corners. The smallest square tin can you can
| find should work best. A tin can sealed with adhesive cooper
| tape should work pretty well even if the copper tape is
| isolated by the paint on the can.
| mcshicks wrote:
| I had to do some testing with ble temp sensors once we're I
| needed to isolate them and then put them in a freezer. They
| were in advertising mode so I could tell at least if I
| could see them with a phone. A round tin that was used for
| green tea from Japan was the most reliable method I was
| able to improvise. It fit very snug and the lid was about
| an inch deep.
| aurizon wrote:
| Yes, a one inch compressed gap like that is a tortuous
| attenuative path in it's own right...
| Terry_Roll wrote:
| How many different biscuit tins did you try? :-)
| jmnicolas wrote:
| Interesting experiment however his experience with tinfoil and
| metal boxes doesn't match mine.
|
| I placed my phone wrapped in a towel inside a metal box: as soon
| as I close the lid I can't ping the phone on local WiFi and can't
| reach it with call (it goes direct to voicemail as if the phone
| was switched off). The GPS doesn't record any position while in
| the box. I didn't test the Bluetooth though.
|
| Same thing for my car keys inside a paper towel and aluminum
| foil: impossible to open the car even at touching distance.
|
| I wonder if he wrapped the device before putting it in the box or
| aluminum.
| mnw21cam wrote:
| I would note that GPS is _much_ more fragile than WiFi
| /Bluetooth/GSM. The GPS signals are already incredibly weak at
| the receiver.
| pluc wrote:
| Surprised slnt.com isn't mentioned. Happy with their product.
| whiw wrote:
| > Faraday cages are non-directional.
|
| Per-se, yes, agreed, but I was wondering whether the transmitter
| and receiver antenna couple into the surrounding screen
| differently. The degree of coupling may de-tune them differently.
| If so then the setup which most accurately represents the
| intended use would be with the receiver inside the screen.
| BongoMcCat wrote:
| > 20 dB represents a change of a factor of 10 in amplitude
| (volts), while 40 dB is a factor of 100, 60 dB a factor of 1000,
| and so on.
|
| I always thought it was 10dB, or one B that was a change of
| factor 10. Have I missed something?
| js2 wrote:
| TIL: _Two principal types of scaling of the decibel are in
| common use. When expressing a power ratio, it is defined as ten
| times the logarithm in base 10. That is, a change in power by a
| factor of 10 corresponds to a 10 dB change in level. When
| expressing root-power quantities, a change in amplitude by a
| factor of 10 corresponds to a 20 dB change in level. The
| decibel scales differ by a factor of two, so that the related
| power and root-power levels change by the same value in linear
| systems, where power is proportional to the square of
| amplitude._
|
| https://en.wikipedia.org/wiki/Decibel
| variaga wrote:
| You're missing the distinction of power vs voltage. dB is
| defined in terms of power.
|
| Power is proportional to voltage squared.
|
| So a 10x increase in voltage == a 10^2 = 100x increase in power
| == a 20dB increase in power.
| Wistar wrote:
| Matt Blaze is a treasure.
| tgb wrote:
| Interesting results. The article states that Faraday cages are no
| directional. My physics 101 understanding of them was otherwise.
| You show they work by integrating over the surface of the cage
| and saying that's equal to the charge _within_ the surface. But
| you don 't say it's equal to the charge outside. Indeed it
| couldn't possible, since that charge could be light-years away
| and steady state would never be achieved. Now that was for
| electrostatic which isn't really what we care about, if I
| remember correctly.
|
| Wikipedia also states they are more effective at blocking
| incoming than outgoing signals. Can anyone clarify the situation?
| pfortuny wrote:
| If you consider the compactification of R^3 by a single point
| "at infinity", an electric charge inside the surface is the
| same as the opposite charge at infinity (this is just Gauss'
| result). In that sense, "infinity" acts as the opposite charge,
| does it not?
|
| I do not understand your question, otherwise.
|
| (Not a criticism, just an interested comment which may be very
| wrong though).
| posix_me_less wrote:
| > If you consider the compactification of R^3 by a single
| point "at infinity", an electric charge inside the surface is
| the same as the opposite charge at infinity (this is just
| Gauss' result)
|
| This is a mental operation, not physically possible. The
| difference is real: for example, charge inside a perfect
| conductor cavity generates electrostatic field outside. A
| charge outside perfect conductor cavity does not generate any
| static field inside.
| tgb wrote:
| This is what I wondered about back in physics class. Does
| that prove the universe is not compact? If it were, then
| inside-outside is the same. But surely that's not enough to
| know the shape of the universe. My 'resolution' of this was
| to say that the universe is surely very large and so the
| time to reach equilibrium will be very very long. So the
| experiment cannot really be run to completion.
|
| But would a point charge outside a conductor cavity ever
| come to equilibrium where it does generate an electric
| field inside the conductor cavity? Assuming compact but
| very large universe. It seems strange but I guess it would.
| pfortuny wrote:
| Aaaahhhhh!!!!
|
| Thank you for this comment, truly enlightening (I am a
| mathematician and know 0 physics). Shall have to think
| about it.
| janekm wrote:
| The pink bag shown is actually a static dissipative bag, not a
| static shielding bag, so would not be expected to work. Though
| the article mentions trying other bags so no doubt some of those
| where static shielding (metallic appearance) bags.
|
| I've had a lot of fun in the past trying to shield Bluetooth
| devices for testing... metal filing cabinet? Practically no
| attenuation. Biscuit tin? Minimal attenuation like in the
| article.
|
| Modern radio receivers are ridiculously sensitive.
| deelowe wrote:
| I noticed this as well.
|
| > "Makeshift Pouch 1: Electrostatic Mylar Bag"
|
| This is not a mylar bag. It's frustrating how often these two
| are confused, especially when said confusion can result in
| component damage.
| gdelfino01 wrote:
| Electronic voting machines should be put inside Faraday cages
| too. Specially now that communication chips have been found
| hidden in some of their motherboards.
|
| https://letsfixstuff.org/2021/04/modem-chips-embedded-in-vot...
| ziggus wrote:
| Solution: Wrap device in aluminum foil, place in Mylar bag, place
| bag in cookie tin.
| noduerme wrote:
| Where I live, all I have to do to block 4G is to stop standing in
| the far corner of the yard.
| shapefrog wrote:
| left arm not in the air and both feet on the ground seems to
| get rid of the 4g signal for me.
|
| I do miss the old days of tuning the rabbit ears on top of the
| tv for best reception.
| Kaibeezy wrote:
| Try this trick... with your feet in the air and your head on
| the ground, spin it.
|
| Did you get an earworm? I sure did.
| djmips wrote:
| If you are sufficiently concerned, why not mod the phone to add a
| physical battery disconnect? Would this not provide 100%
| protection?
| bserge wrote:
| Great idea! Kinda hard on glued smartphones, but still doable.
|
| Just need a switch between the + terminal and the rest of the
| phone, right?
|
| The more paranoid might think there's a backup battery
| somewhere, though.
| marginalia_nu wrote:
| Better still, just leave it in a drawer.
| pdkl95 wrote:
| Even better: practice _defense in depth_ and do both.
| catlikesshrimp wrote:
| If you are concerned enough, but a phone with physical switches
|
| https://www.androidpolice.com/2020/08/22/this-smartphone-has...
|
| Or at least phone with a removable battery
|
| I know I will never buy a phone without a 3.5 audio jack
| haarts wrote:
| That last sentence surprises me a bit. What does a 3.5 audio
| jack have to with any of this?
| catlikesshrimp wrote:
| Manufacturers are always trying to push features that are
| more profitable to them. As expected.
|
| Non-removable batteries is the new standard because of
| that. (Also stream lining) Which is bad for security (the
| point of the article)
|
| I don't use bluetooth because it is not reliable enough for
| me, because I don't like charging another device and, less
| importantly, because in the past it has been exploited to
| hack devices. The audio jack is the one port I prefer never
| to part with.
| jmnicolas wrote:
| What if there's a capacitor inside the phone that has enough
| electricity inside to let the phone ping cell towers?
|
| Depending on your occupation it can have very serious
| consequences.
| lettergram wrote:
| I actually have a little cookie box, which is lined with heavy
| aluminum foil, which I put in a steel lunch box.
|
| Perhaps it sounds like overkill, but it's the only way I seem to
| be able to fully isolate the devices.
|
| That said, I'd probably just buy a bag... but I've been trying to
| keep it with what I have lying around the house.
| yosito wrote:
| I'd be curious if anyone finds it worthwhile to have a smartphone
| while being so paranoid that you have to hide it in a Faraday
| bag. I understand the problem. I just don't understand the
| practical use case: every time you use the phone, you have to
| take it out of the Faraday bag, and it can be used to spy on you
| or report information about you. Assuming you're keeping it in
| the Faraday bag all day, when and why would you find it useful
| and worth the risk to take it out? And with that level of use,
| wouldn't it be more practical to have a dumb phone or a laptop?
| 24bug47 wrote:
| You would take out your phone if you would like to make a phone
| call, or check to see if you have received any messages. For
| the other 99% of your day, the IoT sensors being stuck on every
| conceivable object are unable to report back to HQ (and every
| agency and broker affiliated) your current whereabouts and
| trajectory.
| yosito wrote:
| So why not get a more basic phone and not a smart phone?
| throwaway1777 wrote:
| Dumb phones still ping cell towers?
| yosito wrote:
| Sure, but they also have simpler hardware that's easier
| to audit and almost all have removable batteries, which
| is most likely just as effective as a faraday bag.
| ncmncm wrote:
| I wish it covered (so to speak) aluminum foil more thoroughly.
|
| In particular, foil is cheap, so rolling up in several layers (3?
| 5? 10?) and twisting the ends cracker-style ought to be more
| reliable and practical than trying to do it with one layer and
| fiddly seams. A suggested minimum number of layers and number of
| twists would be useful.
| rasz wrote:
| I was hoping for this test
| https://www.youtube.com/watch?v=2u6KdHmoMbw
| stinos wrote:
| I wish it had covered practical tests more thoroughly. As in:
| did the phone communication effectively drop dead once in the
| cages which measure well? Looks _very_ likely based on those
| attenuation numbers, but still: 'question everything' is
| usually the way to go in test&measurement.
| JohnJamesRambo wrote:
| That was really interesting. I can't believe how poorly the metal
| tin box did compared to real faraday pouches.
| londons_explore wrote:
| The metal tin box will have had varnish and paint on it's
| surfaces.
|
| That means at the junction between the tin and the lid (and
| maybe other joins), there isn't an electrical connection all
| along.
|
| Having two metal surfaces next to eachother, but with an
| insulator in between, acts like a 'choke flange'[1]. However,
| they only work at one specific frequency - at all other
| frequencies they will leak either a little signal or a lot/all
| the signal.
|
| The same technique is used on a microwave door edge to keep the
| microwaves in. It's why keeping the microwave door edge clean
| is critical to safety - a small bit of food there isn't an
| insulator like the paint, and energy leaks out.
|
| [1]:
| https://en.wikipedia.org/wiki/Waveguide_flange#Choke_connect...
| PeterisP wrote:
| What I hear from you is that soldering a wire connection
| between the tin can and its lid should improve it's function
| as a Faraday cage?
| op00to wrote:
| TIL! Thanks!
| rubylark wrote:
| That's interesting! As far as improvised faraday cages go, I
| always heard that microwave ovens are a good solution. Does
| this mean that microwave ovens wouldn't be any better as they
| would only block the specific microwave frequency they're
| designed for?
| londons_explore wrote:
| Correct. In fact, you can easily verify this by putting a
| phone in an unpowered microwave and calling it. It'll
| usually get both 4G (frequencies range, but 800Mhz in my
| area) and Wifi (over 5GHz).
| coldacid wrote:
| I wonder how many of us are going to end up cleaning our
| microwaves today after seeing this comment.
| fpoling wrote:
| I visited at the end of eighties a research institute in a former
| USSR. They had a whole room with computers put in a Faraday cage
| to prevent any data leaks with supposedly secret information. The
| cage was a mesh made of thin metal sheets with 1mm holes. As I
| remember the whole thing was done seriously, not a fake to please
| some inspector. It had double doors, all cables were put into
| metal tubes, all lights were outside I suppose to minimize the
| cabling.
| [deleted]
| dsign wrote:
| Cheap science fiction book idea: imagine having to choose between
| living without your smartphone or living with every company and
| government agency willy-nilly spying on you. Oh, wait...
| motohagiography wrote:
| Glad to see these tested. I've been using the EDEC bags for
| probably a decade to have on hand for incident response/forensics
| in security consulting, but I never had the gear to test the
| bags, I just trusted their supplier. Good to know about
| millimeter wave / 5g though.
| f38zf5vdt wrote:
| If all phones were mandated to have a physically isolating means
| to disable their wireless chips, we could avoid this problem all
| together.
| 0xdeadb00f wrote:
| Even then, how could you trust that the physical isolation
| switch is enough?
| WalterBright wrote:
| > The question is, then, how well do they actually work?
|
| I tested some by putting the phone in the Faraday container, and
| then calling its number to see if it rang.
| 0xdeadb00f wrote:
| Wrapping your phone in aluminum foil also works.
|
| I've made a few DIY Faraday bags that way. They're not perfect of
| course, but less expensive than these bags most of the time.
|
| Edit: Ah, I see this was covered in the article. I didn't read it
| before posting this comment.
| taneq wrote:
| It also keeps them from drying out when you microwave them
| while still maintaining a crispy skin.
| Kaibeezy wrote:
| Also, caution: If your phone is made from a tomato or other
| acidic substance, the foil may corrode, further reducing RF
| containment.
| dotancohen wrote:
| I believe that the Tomato is more commonly used for routers
| - this may be why!
|
| A good portion of phones, on the other hand, do seem to be
| made of the fruit of the domesticated Malus.
___________________________________________________________________
(page generated 2021-12-02 23:02 UTC)