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How to find a lost phone in a no-cell-coverage camping site?

manas.tech

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Re: How to find a lost phone in a no-cell-coverage camping site?

#51

Post by jffry »

lxgr wrote: post #40
WanderPanda wrote: post #37

Earlier quoted context omitted.

Not to nitpick but I think you mean trilaterate ;)

If we're being nitpicky it was probably neither – multilateration requires taking multiple measurements, drawing circles/lines of equal signal strength (or timing advance) and then intersecting these. If you just want to home in on a transmitter, there's a much simpler algorithm: Try walking into various directions and keep heading into the one that makes the signal strength nunber go up :) Not sure if there's a name…

> Not sure if there's a name for that.

Hill climbing! https://en.wikipedia.org/wiki/Hill_climbing

Basically: Go in any direction that makes the number go up. Repeat.

Re: How to find a lost phone in a no-cell-coverage camping site?

#53

Post by lxgr »

askvictor wrote: post #28

What's the difference in signal strength between bluetooth and wifi? I had assumed since they use the same frequency, and usually the same chip and antenna, they would be much the same (perhaps there are regulatory differences between them?) If anything, I'd guess that BLE would be more useful in this case as there is less handshaking, which means on a very poor connection you've got more of a chance of getting some…

Depends on the Bluetooth device class.

Most devices are Class 2, with a maximum transmit power of only 2.5 mW; that's not a lot compared to Wi-Fi's ~20-30 mW.

AirPods are notably Class 1, which goes up to almost 20 mW! They accordingly have much better range as a result.

Bluetooth LE in newer version has new low-bitrate coding methods to allow for even greater ranges (called "Coded PHY"). Assuming Bluetooth LE classes are the same as for EDR (I don't know if they are!), this source [1] claims a 4 times greater range using coded PHY, which would be in the range of several hundred meters.

[1] https://www.bluetooth.com/blog/exploring-bluetooth-5-going-t...

Re: How to find a lost phone in a no-cell-coverage camping site?

#54

Post by lxgr »

dharmab wrote: post #50
lxgr wrote: post #40

Earlier quoted context omitted.

If we're being nitpicky it was probably neither – multilateration requires taking multiple measurements, drawing circles/lines of equal signal strength (or timing advance) and then intersecting these. If you just want to home in on a transmitter, there's a much simpler algorithm: Try walking into various directions and keep heading into the one that makes the signal strength nunber go up :) Not sure if there's a name…

Direction finding! https://en.wikipedia.org/wiki/Direction_finding

I was looking at that too, but doesn't that usually imply using a directional antenna, rather than just measuring the received signal strength at different locations?

Re: How to find a lost phone in a no-cell-coverage camping site?

#55

Post by gauravphoenix »

This reminds me of the kind of hack I came up with, almost 20 years back. I used to work in Bangalore, and now and then, we would have a power outage in the evening that lasts for a few hours. I was single and used to live alone. I did not want to go home from the office and find myself without power. So how do I find out there is power at home? During those days, there were no IOT devices so checking them is that's out of the question. But I did have a landline phone that was powered by electricity and had a replaceable battery as a backup. I used the phone only to connect to the internet. So I just removed the batteries and when the power goes out, my phone wouldn't 't work. So before leaving work, all I had to do was call my landline. If it rings, it means there is power.

Re: How to find a lost phone in a no-cell-coverage camping site?

#56

Post by lxgr »

solardev wrote: post #19
marcod wrote: post #4

So, there is no security feature that prevents a phone from connecting to a cloned wifi network??

Yeah, back in the day before HTTPS was common, this used to be a viable attack where people would set up rogue hotspots at cafes and whatnot and intercept all your traffic.

That's only possible for unencrypted networks/SSIDs, though.

Re: How to find a lost phone in a no-cell-coverage camping site?

#57

Post by lxgr »

dhosek wrote: post #6
marcod wrote: post #4

So, there is no security feature that prevents a phone from connecting to a cloned wifi network??

How can you tell a wifi network is cloned if the SSID/password match? After all, it might legitimately be a new legitimate access point in the network.

Exactly, if the SSID and password match, it is the same network by definition.

Re: How to find a lost phone in a no-cell-coverage camping site?

#58

Post by lxgr »

redox99 wrote: post #8
dhosek wrote: post #6

Earlier quoted context omitted.

How can you tell a wifi network is cloned if the SSID/password match? After all, it might legitimately be a new legitimate access point in the network.

Obivously using certificates and TOFU. APs would share the certificate. (That's how it should work, not how it does in practice)

It's not that easy, unfortunately: Many networks span more than one access point, either simultaneously or across time (mediocre CPEs are notoriously being swapped out all the time by cable providers, in my experience).

Initially loading and then synchronizing certificates across APs would be anything but trivial.

I've surprised my friends a few times by keeping my SSID + password constant over the years and across several moves within the city (and across ISPs) and even internationally – whenever they come to my place, they have Wi-Fi the second they step through the door :)

It's also nice not having to re-configure various embedded devices, many without a sane user interface to type a passphrase or even accept a new TOFU public key, every time I set up a new router at my family's place.

Re: How to find a lost phone in a no-cell-coverage camping site?

#59

Post by theendisney2 »

In my job I regularly wonder how to get a found phone laptop or notebook back to their owner. The notebook is the easiest. The apple laptop the most stupid. I have the locked laptop i have my iphone you would think, with the closed eco-system, there to be some magic ritual i can perform for the laptop to register on the owners "find my device"???? Or at least let me type a number for them to call?

Sometimes, (if i charge the phone) eventually contacts real names appear on the home screen. This seems just the information one shouldn't be sharing?

It is really odd how garbage the tech is here.

Re: How to find a lost phone in a no-cell-coverage camping site?

#60

Post by solardev »

lxgr wrote: post #56
solardev wrote: post #19

Earlier quoted context omitted.

Yeah, back in the day before HTTPS was common, this used to be a viable attack where people would set up rogue hotspots at cafes and whatnot and intercept all your traffic.

That's only possible for unencrypted networks/SSIDs, though.

I think that's a different attack, where you could passively sniff wifi traffic from networks without WEP. I meant more just hosting your own hotspot with a popular name, forcing clients to connect to it via disconnect/reconnect attacks, and then you're essentially a tiny MITM ISP that can monitor all their unencrypted traffic
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