How does Apple privately find offline devices? • Hacker News Board

Re: How does Apple privately find offline devices?

#71

Post by xvector » Wed, Jun 05, 2019, 11:32 PM UTC

SlowRobotAhead wrote: post #2

>can use a single [private] key regardless of which randomized version of her public key was used to encrypt. I have not seen this before. Trying to wrap my brain around how this works. In terms of ECC I thought public and private were a single pair. Can anyone explain what is going on with public key randomization?

The article gives the example of El Gamal encryption [1]. Looking at the key generation section, it seems like you could keep a single (q, x) pair and create a new (G, g, h) for the same x.

Re: How does Apple privately find offline devices?

#72

Post by Operyl » Wed, Jun 05, 2019, 11:33 PM UTC

gervase wrote: post #33

honopu wrote: post #26

Earlier quoted context omitted.

Did not know this. I figured all those wifi connections I get near stoplights were slurping up mac addresses to track people. I wonder if it generates a mac address every single time or just upon first interaction with a wifi network it doesn't know about?

Apparently the initial implementation (iOS 8) randomized it every time the screen sleeps or wakes. I wasn't able to find any recent documentation detailing the current behavior - probably similar?

Beginning at the top of page 41: https://www.apple.com/business/site/docs/iOS_Security_Guide....

``` iOS uses a randomized Media Access Control (MAC) address when conducting Wi-Fi scans while it isn’t associated with a Wi-Fi network. These scans could be performed in order to find and connect a preferred Wi-Fi network or to assist Location Services for apps that use geofences, such as location-based reminders or fixing a location in Apple Maps. Note that Wi-Fi scans that happen while trying to connect to a preferred Wi-Fi network aren’t randomized.

.... [continues with all the cases] ```

Re: How does Apple privately find offline devices?

#73

Post by pfranz » Wed, Jun 05, 2019, 11:33 PM UTC

evan_ wrote: post #65

rootusrootus wrote: post #17

Earlier quoted context omitted.

Wouldn't this be already possible (and a lot cheaper) using something like Tile?

Yes, except you'd need to get your target to install the Tile app and use it frequently enough that it keeps background location privs. If Apple does come out with a cheap Tile-type device with a then this could be a legit concern. If you hid one in a person's belongings then you'd get hits from their phone- and turning it off wouldn't work, because random passersby would report their location as well. This could eve…

What I understood the parent to mean would be to buy and register a Tile yourself, then hide that on your victim.

Using the same type of "mesh network" Apple mentioned, other users you can track that Tile for you: https://youtu.be/WG7BdW7iFzo?t=58

(I'm not familiar enough with Tile to know if that feature is continuous, but I wouldn't be surprised if a competitor does).

Re: How does Apple privately find offline devices?

#74

Post by crazygringo » Wed, Jun 05, 2019, 11:35 PM UTC

Can this be used as essentially 100% effective anti-theft?

If an Apple device is constantly emitting a BLE beacon code that can't effectively be changed in any way by a thief...

...then unless a thief keeps the device in their basement and never has anybody visit, your stolen device will almost certainly be detected sooner or later, and then you just call the police?

Even if the thief has sold it by that point and disappeared, if local law means the stolen good reverts to you, then people would quickly learn never to purchase any phone there's even a chance of having been suspiciously acquired.

Am I missing something here?

Re: How does Apple privately find offline devices?

#75

Post by Phlarp » Wed, Jun 05, 2019, 11:36 PM UTC

crazygringo wrote: post #70

RosanaAnaDana wrote: post #48

Earlier quoted context omitted.

Sure. I pulled my data in the standard takeout.google.com/ process. The result is a json (? iirc). I parsed the json into x, y, and rasterized it using gdal. https://imgur.com/a/ZhyTsDV See I wasn't sure if I lost it in the couch in the living room, the office, or the bedroom. This got me within a few feet.

That's amazing, so cool. Is that something Google's not doing with the data, but could? (E.g. they don't because their maps don't show most houses precisely enough or whatever, so it wouldn't be useful?) Or is it relying on the fact that you are triangulating or similar from the known exact position of your WiFi routers or similar down to the inch, and Google doesn't have any way of knowing that?

Or they do and have internally assessed that it would be too creepy to provide to users, but are happily using it to better target advertising.

Re: How does Apple privately find offline devices?

#76

Post by Phlarp » Wed, Jun 05, 2019, 11:39 PM UTC

snazz wrote: post #64

etaoins wrote: post #51

Earlier quoted context omitted.

The T2 chip is a derivative of the A10. It has similar power requirements to the SOC in modern iPhones. They could probably use a cut down derivative of the W2 chip used in AirPods with the audio codec etc. removed. I’m guessing phone batteries reach a point where they’re still storing energy but can’t provide enough current to safely boot the whole phone. The BLE chip could sip on the remainder of the battery for a…

That sounds reasonable. I had no idea the T2 was that powerful.

It's also the SSD controller, and quite impressive in that regard.

Re: How does Apple privately find offline devices?

#77

Post by tinymint » Wed, Jun 05, 2019, 11:41 PM UTC

crazygringo wrote: post #74

Can this be used as essentially 100% effective anti-theft? If an Apple device is constantly emitting a BLE beacon code that can't effectively be changed in any way by a thief... ...then unless a thief keeps the device in their basement and never has anybody visit, your stolen device will almost certainly be detected sooner or later, and then you just call the police? Even if the thief has sold it by that point and di…

Not 100% effective - device could still be stolen and parted out

Re: How does Apple privately find offline devices?

#78

Post by flattone » Wed, Jun 05, 2019, 11:46 PM UTC

crazygringo wrote: post #70

RosanaAnaDana wrote: post #48

Earlier quoted context omitted.

Sure. I pulled my data in the standard takeout.google.com/ process. The result is a json (? iirc). I parsed the json into x, y, and rasterized it using gdal. https://imgur.com/a/ZhyTsDV See I wasn't sure if I lost it in the couch in the living room, the office, or the bedroom. This got me within a few feet.

That's amazing, so cool. Is that something Google's not doing with the data, but could? (E.g. they don't because their maps don't show most houses precisely enough or whatever, so it wouldn't be useful?) Or is it relying on the fact that you are triangulating or similar from the known exact position of your WiFi routers or similar down to the inch, and Google doesn't have any way of knowing that?

Perhaps this level of location resolution is not stable enough at Google scale to present it? AKA: better to show reliable fuzzy information than unreliable precise information.

Re: How does Apple privately find offline devices?

#79

Post by LeoNatan25 » Wed, Jun 05, 2019, 11:47 PM UTC

walterbell wrote: post #61

m463 wrote: post #59

Earlier quoted context omitted.

recent apple phones have NFC, which cannot be disabled.

Can NFC be used by iOS applications, e.g. SSH authentication via smartcard, where the private key never leaves the card?

I think it is possible in iOS 13, unless I misread the WWDC video description.

Re: How does Apple privately find offline devices?

#80

Post by kccqzy » Wed, Jun 05, 2019, 11:57 PM UTC

crazygringo wrote: post #74

Can this be used as essentially 100% effective anti-theft? If an Apple device is constantly emitting a BLE beacon code that can't effectively be changed in any way by a thief... ...then unless a thief keeps the device in their basement and never has anybody visit, your stolen device will almost certainly be detected sooner or later, and then you just call the police? Even if the thief has sold it by that point and di…

Thieves already know that stolen iPhones are usually not operable. Even with the old Find My iPhone, even after the device has been wiped, only the original owner can activate it again. So these stolen phones are usually broken down, with parts sold separately.