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Comment by sillysaurus3 | Hacker News Reader

Actually, you can buy some paint that blocks all RF signals. It's absurdly expensive but quite effective. There aren't many ways to get signals out of a room painted with the stuff.

If you're thinking "Why not just build a faraday cage?" then you're thinking the right thing.

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Actually RF shielding paint is very poor. Manufacturers advertise them with "99.5 %" or so, which equates a measly 20 dB. Additionally, correctly applying these is quite difficult, and incorrect application greatly diminishes the shielding. (You also need to cover everything, including ceiling and floor, not just the walls). Even when correctly applied, the attenuation is so weak, a cell phone will still work. Shielded facilities are built differently and are far more expensive than shielding paint.

RF dead chambers are bloody expensive for a reason: you can't emulate them by pasting some paint on a wall.

> RF dead chambers are bloody expensive for a reason: you can't emulate them by pasting some paint on a wall.

Couldn't you just stick yourself in a metal box (with a metal door that is careful to get a good seal)?

Well yeah, that's what those chambers are. Except it's a bit more complicated to do than "just" :)

How do you propose to breathe in there?

By opening the door when not in use.

If you need continuous use, two rooms. One that acts as an "airlock" with an outer door that is open only when the door to the other room is closed. Battery operated fans and lights used as necessary.

Note that the "inner room" might be as small as a ammo crate depending on your use case.

One of my first jobs was building shielded boxes for a sensitive RF measurement setup. Containing the RF output from something like a laptop is hard. I lined the inside of the boxes with copper beryllium mesh (attached with glue, since nails become little antennas), soldered all the joints to ensure electrical continuity, and put a copper beryllium gasket all around the lid to make sure there was continuity when the box was closed.

I've thought about turning my whole house into a faraday cage way too many times to be considered sane still.

It's fun, isn't it? It's one of those things that costs way too much to be practical but you can't help but try to think of ways to get the cost down. Mini-SpaceX in a useless domain.

I've always thought that would be cool, then just have a fiber connection for communications and either air gap your main power or provide your own via solar and wind.

Ermmm we used the copper nanotube paint once on an office and, well, it sucked. Bad. Cell phones only worked in this small corner of the office, and wifi was chaotic. Something about signals can't get in, but they also can't get out, so they collide ...

I think the word you're looking for is "reflect."

Yes, thank you. Reflect. It created considerable interference.

Isn't there RF-blocking wallets? Seems like something I'd probably buy if I had an identity worth stealing.

I have one of those and it's kind of a PITA. I actually didn't realize it blocked RF until after I bought it. It's annoying because I can't just tap my wallet on the MUNI gates or the card reader at work, I have to open up the damn thing and press the edge of the card poking out of the card holder against it and hope it works (sometimes it does, sometimes I have to pull out the card).

I probably just have too much junk in my wallet, but I can't ever just tap the wallet against an NFC reader anyway. It either doesn't read anything or it reads one of the other low-power NFC cards contained (I think I have 3-4). For quick access to a single card maybe you can get a lanyard or one of those retracty thingies people wear around their belt loops?

Well, if I was doing security at your company, I'd probably want employee credentials to be visible at all times, which would also happen to take care of your problem.

Employee credentials should not be visible when the employee isn't inside a secured area. If you work at a site with a Security Officer, try inviting them out to lunch and not hiding your credentials. See if they care.

> "Why not just build a faraday cage?"

Then my very next thought is, "Who is going to notice my house-sized faraday cage, who are they going to tell, and what are those people going to do in turn?"

Lan party.

If Howard had known of this paint, then he wouldn't have had to put Mylar all over his house and look like a kook! Jimmy wouldn't have had to do so much to help him out... maybe he'd still be alive!

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