How does Apple privately find offline devices?

https://blog.cryptographyengineering.com/2019/06/05/how-does-apple-privately-find-your-offline-devices/

by kandarpck • 7 years ago

347 179 7 years ago

blog.cryptographyengineering.com

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?

philipkiely• 7 years ago

Warning: this is baseless speculation from someone with only a semester of cryptography experience.

If you asked me to implement "randomized public keys" I would generate a master key pair (MPUB and MPRIV). Then, I would combine MPRIV and a random value N in a one-way function to make a new key K. I would use K as effectively a "random public key" and use it as if it was MPUB (the one-way function would have to output a K that is in the same format / usable like MPUB). I would distribute N along with K, as N is useless without MPRIV.

I have no idea if that is how they did it but that's what comes to mind.

ryanmarsh3• 7 years ago

Warning, no academic crypto experience but I've used it in production systems. Oh the horror.

Couldn't "random value N" just be a nonce that only Apple knows?

Scaevolus• 7 years ago

You can derive a new public key from someone's ECC public key, and they can derive the corresponding private key by applying the same transformation. It's somewhat magical! I wouldn't be surprised if Apple is using a scheme based on this instead of ElGamal, they already use ECC extensively.

https://github.com/bitcoin/bips/blob/master/bip-0032.mediawi...

snarf212• 7 years ago

Interesting, I hadn't thought of using the techniques of deterministic cryptocurrency wallets to solve this problem. I need to read more about exactly how they work.

It is also easy to solve this simply using ECC and ECDH. I just wrote a scheme on the board in the office. It might have slightly larger data payload than the deterministic wallets approach.

xvector2• 7 years ago

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.

Too• 7 years ago

Just speculating but would something like random_key=hash(static_key + datetime) work? static_key is pre-shared between cloud and device and datetime is also known by both device and cloud if rounded down to some accuracy.

kohtatsu• 7 years ago

The post is speculation; perhaps s/does/might/ or s/does/could/ in the title.

pwinnski2• 7 years ago

Not so much; most of the article restates in simpler terms what Apple has outlined as reported in Wired[0].

[0] https://www.wired.com/story/apple-find-my-cryptography-bluet...

Fnoord2• 7 years ago

The title is a question. Which is why it ends with a questionmark. The article attempts to answer the question with theories. The article isn't written by Joe Random; it is written by Matthew Green who teaches cryptography at John Hopkins university.

helper• 7 years ago

Johns* Hopkins.

m4637• 7 years ago

Can we turn this off? please?

I would like 100% passive bluetooth. (and wifi, and nfc)

Xylakant2• 7 years ago

How is that going to work? All communication that you initiate must be active. The only passive option would be broadcasts like TV or radio stations, but that’s not particularly useful if you want to view a specific website.

berbec2• 7 years ago

NFC is passive until powered by an external signal. It's very short range, but it does not require internal power. There could be a longer range version at some point.

RosanaAnaDana7• 7 years ago

Could be more like a key RFID. Like, the system could have died, its antenna has been restructured to work like an RFID; so if there is a live device in the area, it can resonate and generate a slight signal.

Nition• 7 years ago

Just cycle though every website on the Internet and have the PC pause when the requested page is loaded obviously. It worked for Teletext.

m4637• 7 years ago

I meant, don't turn your phone into a beacon. (as a setting is ok)

The idea would be yes -- connect to bluetooth headphones or your car. Connect to wifi in your home. Allow NFC transactions on command.

But no, don't promiscuously advertise your device. Don't look up every bluetooth beacon you encounter or crowdsource every wifi access point.

ShakataGaNai2• 7 years ago

The problem I see with this is that your phone always has to be broadcasting the BLE beacon, regardless of if it is lost or not. Otherwise it could randomly end up lost in a place with poor/no service... and would never be found

For phones, how often is this really an issue? Sure, this is useful for the Tile type "dumb" devices... but if my phone has no cell or data service... it's probably because the battery is dead.

Uehreka• 7 years ago

Some people have hypothesized that this isn't necessarily for finding phones. This might be about using phones (and iPads, Apple Watches, MacBooks, etc.) to create a network like the one used by the Tile product for finding wallets, keys, etc. This could be a product Apple unveils in September.

m0dest• 7 years ago

This is for tracking lost MacBooks. Apple said this at the keynote. They may expand it beyond laptops, but that's the initial scenario. (It's a great one.)

Slippery_John• 7 years ago

I can think of several scenarios:

* I lost the phone hiking somewhere with no signal

* I lost the phone / it was stolen while in airplane mode

* I lost the phone while traveling abroad without any local service

This finding service will work for wifi-only ipads, wifi-only apple watches, and macbooks in addition to the likely tracking tokens.

Fnoord2• 7 years ago

Stolen while in airplane mode, and you're going to rely on BLE? A "good" thief would learn that he'd need to carry around a Faraday cage (read: some tinfoil) to block the signals. The only disadvantage is that the act of putting tinfoil around an iPhone then becomes suspicious.

rootusrootus2• 7 years ago

Given how little power it takes to operate something like a Tile, maybe the beacon will continue operating for quite a while after the battery is too low to operate the whole phone.

ladberg2• 7 years ago

Complete speculation here, but I wouldn't be surprised if devices could keep broadcasting the ping after they're "dead". Tiles last for years without charging, so I bet if Apple can leave on only the bluetooth beacon after the battery drains past where it can power the rest of the phone then this would be doable.

Again complete speculation, I have zero clue if the current hardware is even capable of doing this.

snazz2• 7 years ago

The current hardware might not be, but you could run this on a secondary chip similar in specs to the T2 or Secure Enclave. You could theoretically even have a second battery specifically for this purpose, but that would likely be cost-prohibitive.

m4637• 7 years ago

recent apple phones have NFC, which cannot be disabled.

president2• 7 years ago

Also, couldn't the BLE beacon be used by "smash and grab" thieves to find devices in your car?

m-app2• 7 years ago

Yes, and this is already happening due to the feature that Macbooks have to connect to eg. BL keyboards and mouses. Perhaps also the "Smart Sleep" function (not sure what it's called exactly) that periodically connects to Wifi to fetch emails so they're there when you open your Mac again. This has happened to me and other folks here in NL, by the way.

MBCook2• 7 years ago

Don’t think phone. In the keynote I think they showed it with a Mac, which isn’t available with cell service. Or as someone else mentioned maybe you have an iPad without cellular.

It would be useful for those.

ShakataGaNai2• 7 years ago

Fair point. For wifi only devices, I could see it having some use.

xt00• 7 years ago

Apple is highly averse to having your phone send out any BLE beacon all the time. Likely what they will do is the following:

1) The iPhone will be considered the "master" (aka BLE Central device)

2) All of your devices that you enroll in your "find my" service will be required to sending out a periodic BLE beacon or a similar bluetooth packet (BLE peripheral device)

3) The iPhone will periodically listen for BLE beacons and upon receiving that beacon it has 3 options:

->option 1, save the time/location when it saw that beacon

->option 2, scan the device with a BLE "scan request" operation which asks the device to provide more information -- it provides the "scan response" packet which can and often is different from the main advertisement packet

->option 3, connect to the device and query further information like your macbook battery level and maybe other info

For option 1, the iPhone never needs to send a packet ever and will simply have its BLE RX radio stage on listening for advertisement packets -- which are sent in clear text for anybody to listen to. The RX stage is listening periodically and works on a statistical basis where if the beacon side is transmitting very rarely then you can easily miss the beacon.

So.. what you should take away from this is that highly likely Apple will only allow the iPhone to be the master and all of your other devices will be periodically sending out beacons. So if you have this enabled and you walk around with your iPad Pro and your iPhone together and people sniff bluetooth packets, they can track when you walk down the sidewalk past you every day. For example if you live near a busy street in New York or something, start sniffing for bluetooth packets and you'll find tons of stuff. Tons.. most of it is random bluetooth headphones, but pretty soon it will be iPad Pro's.

taneq• 7 years ago

your phone always has to be broadcasting the BLE beacon, regardless of if it is lost or not

It could have an X-hour "deadman timer" after which if it still hasn't successfully phoned home and been told it's not lost, it starts pinging?

RIMR• 7 years ago

Okay, so this would make it insanely easy to stalk any iPhone user.

1. Get BLE tracking tags, and register them with Find My.

2. Covertly attach the BLE tracking tags to things your target owns (backpacks, cars, bikes, etc).

3. You constantly get updates on your tags locations via their iPhone and other iOS devices near the BLE tag(s). This gives you their approximate location and movement history, facilitated primarily through their own iPhone and data plan.

dmitrygr2• 7 years ago

I have no idea how the FindMy BLE system works, but i strongly suspect that the cheaperst compatible "tag" you will find will be an iPhone. Might get a tad expensive to do this...

bdcravens• 7 years ago

The potential of low cost tags is in the first paragraph, and an overview of how the system would work is in the second. My takeaway is that you will be able to use something far cheaper than an iPhone.

judge20202• 7 years ago

Assuming the newest ipod touches will work with this, $200 is the cheapest you could do this with in terms of using an iOS device (not that i'm suggesting this is a great option. As pointed out by the other second-level comments, you could just use tile or a real gps tracker without needing iOS).

pwinnski2• 7 years ago

The only "BLE tracking tags" reported to use Find My are Apple devices, and if you can attach an Apple device to something your target owns, there are many means you can use other than Find My to track them.

I mean, if you can accomplish step 2, you don't need Apple at all.

MBCook2• 7 years ago

They are widely expected to introduce such tags later this year.

rootusrootus2• 7 years ago

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

evan_• 7 years ago

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 even be better (worse) than spy-gear standalone GPS trackers because the battery would last for a very long time.

applecrazy• 7 years ago

One of the fundamental rules of security is that if your adversary has physical access, it's over. This sounds like that but with extra steps. If somebody has access to your equipment and am able to attach arbitrary items to your bag, then it could be any tracker (Tile, cheap GPS tracker, iPhone, etc.), then of course it's over from a security perspective.

imhoguy2• 7 years ago

I see lots of poor Lassies in airports, conferencies and generally in crowded places. Not even mentioning flood or replay attacks.

Lassie's help needs to have some limits otherwise it may quickly drain batteries or mobile plans especially in roaming.

stouset• 7 years ago

BLE is insanely battery-efficient. And in most scenarios with a lost device, it's either stationary or will be stationary for a sufficient period of time to be discovered, so a ping only once every hour is probably more than enough to locate it. Or a ping with exponential backoff as battery depletes.

Sending the locations from these pings likewise also uses negligible battery, as Apple already coalesces timers and network traffic like push notifications.

I don't understand the mentality where people think Apple would have announced this without doing any testing on its battery life impact.

photojosh3• 7 years ago

Yep. I have a BLE speed sensor on my bike which runs off a CR2032 coin cell. It's been two years of daily commuting and I've yet to change the battery.

saagarjha• 7 years ago

It's Bluetooth Low Energy, though. Should last for quite a while?

randyrand• 7 years ago

"Apple's recommended setting of 100 ms advertising interval with a coin cell battery provides for 1–3 months of life, which increases to 2–3 years as advertising interval is increased to 900 ms."

iPhone's have about at 10X larger batter than that. So iPhones can do this for ~20-30 years if configured correctly.

ryanmarsh3• 7 years ago

If I'm not mistaken the normal self-discharge rate for a phone's lithium ion battery will exceed the maintenance of BLE advertisement.

imhoguy2• 7 years ago

It is not about BLE beacons. Right, they are energy efficient. But receiving party needs to listen constantly and proces these messages. With 1000 beacons around at 1s interval it means the intermediary node needs to send 1000 notifications per second to Apple. That can be buffered and optimized, but still it is some non-trivial number and possible bottleneck to be exploited.

diminoten3• 7 years ago

I'm quite sure they've solved for this particular problem, or they wouldn't have launched the product...

RosanaAnaDana7• 7 years ago

Total aside, but kinda relevant.

I lost my phone like a dufus about a two weeks ago. Battery died and I had no idea where it was. When I pulled the my google location history, it was too coarse to tell me anything other than 'at your house'. However, I was able to pull the raw data from google and post process it by time stamp into a series of rasters that were fine enough for me to see that the phone was definitely in the bedroom/ bathroom area. After processing my data, finding my phone took all of a minute.

mehrdadn• 7 years ago

This is interesting. By the raw data you mean from Google Takeout, or something else? Did you have to filter/smooth the data points?

machinesmachine• 7 years ago

Also interested. Could you describe the process?

jdironman• 7 years ago

Probably just looked at the last data point depending on the type of data was available. If its longitude / latitude values then its going to be pretty precise, although I would also like to know where to pull more granular data.

lawrenceyan• 7 years ago

Point clouds save the day!

rmorey• 7 years ago

This rules, thanks for sharing!

raxxorrax2• 7 years ago

Probably slower than just keep searching. But way cooler.

hugi• 7 years ago

Plot twist: That's actually the queen and she lost the phone in Windsor Palace.

RosanaAnaDana7• 7 years ago

Well, I looked for a week-ish, and was fap-all out of ideas where it was. I was at the point where I was looking in ridiculous locations (freezer, garage, washing machine, garden, tool shed).

This took about 20 minutes to hack together, and I found the phone in 10 minutes of looking in the 'right' spot. My phone had fallen behind the bedside stand and found a way to balance itself between the bed and the baseboards. The bed post is ~phone width, so even looking, you just couldnt see it.

That being said, I work in the geospatial sciences doing geospatial data processing, so 20 minutes for me may not be 20 minutes for some one else.

JohnFen2• 7 years ago

The good news is that Apple claims that their system actually does provide strong privacy, and that it accomplishes this using clever cryptography.

But that does nothing to protect your privacy against Apple.

I already have to make sure that I disable WiFi and Bluetooth when I enter commercial establishments. Now I have to stop using Bluetooth whenever I leave my house?

berbec2• 7 years ago

It gets worse: if you turn off wifi/bluetooth in control center, it only disconnects, keeping the radio active.

1: https://support.apple.com/en-us/HT208086

judge20202• 7 years ago

As it says on the page, this is to make sure a bunch of things still work (eg. you wouldn't really thing you need to keep Bluetooth enabled to use the pencil). Maybe the toast text "disconnecting nearby Wi-Fi until tomorrow" could be a little clearer.

SHAKEDECADE• 7 years ago

You can use shortcuts to disable and enable things.

I use one labled ‘Car’ that turns off wifi, enables cellular data and BLT for the stereo and terminates after it ensures my (non-DNS) VPN is on. The other, ‘Home’ turns off cellular data and BLT, wifi on and again ensures my VPN is still active.

Also if you’ve got anything newer than a iPhone 6, you can 3D touch the settings icon to a pop-up menu to Bluetooth, Wi-Fi, Cellular Data and the Battery sub-menus. From there it’s an extra tap or two to disable stuff completely.

Formatting is likely terrible, I mobile-phoned this in..

ladberg2• 7 years ago

Why do you do that? All Apple devices generate randomized MAC addresses for networks that they haven't connected to, so they shouldn't be able to track you. In addition, no other actors will be able to gain useful information from the bluetooth pings, they simply forward the encrypted data to Apple. All they can tell is that an Apple device exists nearby, but not who owns it or if they've seen the same device before.

If you're talking about apps on your phone tracking you by looking at nearby wifi networks, then Apple also fixes that in iOS 13.

honopu• 7 years ago

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?

JohnFen2• 7 years ago

Why do you do that?

The short answer is because it makes me feel better.

The long answer is that it prevents tracking my movements within a store. Stores appear to be increasingly installing and using such trackers, and I do not wish to be tracked.

Not being able to be identified personally, or to be identified as the same person who was there last week or that I also went into other stores isn't sufficient to me.

m4637• 7 years ago

...Unless you have a private wifi AP you connect to. Then your device is individually identifiable and trackable.

In addition, I believe apps that use ibeacon technology can respond to specific ibeacons. But I think your phone can become a beacon.

I suspect (but am not certain) that if your phone is running app XYZ it can talk to other phones running XYZ through the XYZ registered beacons (if location services are on for app XYZ).

Also, just for an interesting example of where some of this stuff can go... The target app will change the price of an item if it finds you are in a store (search "target app price switch").

JulianMorrison• 7 years ago

If this "no privacy from Apple" widget is using separate low power or parasitic power circuitry, it is entirely possible for it to be running and operational in a switched off phone with a battery on 0% charge.

Buy a Nokia, perhaps?

doctoboggan• 7 years ago

Did you read the article? The author discussed exactly how they are able to hide sensitive data from Apple.

xvector2• 7 years ago

But that does nothing to protect your privacy against Apple.

Absolutely not true. This is E2EE. This is the whole point of the article.

crazygringo2• 7 years ago

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?

tinymint• 7 years ago

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

SmellyGeekBoy• 7 years ago

If only Apple would sell spares through official channels, it would reduce the incentive to steal iPhones even further.

kccqzy• 7 years ago

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.

president2• 7 years ago

They are getting smarter. A family member had their phone stolen and Find My iPhone reported that the phone was off for months and so she gave up searching. One day, she got a text on her new phone saying "Find my iPhone has found your phone, click here to login to Find my iPhone". It turned out to be a phishing page for her AppleID credentials. She fell for it and I'm assuming the thieves were able to finally get into her phone. To this day I have no idea how they were able to get her phone number. From the SIM maybe?

xrjn• 7 years ago

Whilst I was in China two years ago, someone mentioned that you can swap out the memory of an iPhone with one from another iPhone (e.g. water damaged) to get around an iCloud lock. So although it's quite sophisticated as a method, it's definitely doable.

kelnos• 7 years ago

I would assume that a factory reset would take care of it. Otherwise you couldn't sell the phone to someone else and revoke your ability to find it.

schrodinger• 7 years ago

You can’t do a factory reset without the device password.

matt-attack• 7 years ago

You have to do a full iCloud logout which involves your iCloud password in order to disassociate a device from your Find My Phone. It's actually quite involved.

scarejunba• 7 years ago

I assure you the police will do nothing.

freen• 7 years ago

This sounds like the perfect infrastructure for a trusted, encrypted P2P mesh network.

ryanmarsh3• 7 years ago

I designed a similar system a few years back to provide proof-of-presence. Imagine a block chain of devices at locations (an alibi lets say). All devices are miners and only devices in your vicinity (think BLE) can "confirm" "transactions" (your presence) on the chain.

As with anything public + blockchain it had all the Cryptoeconomics incentives problems you would expect and I never solved them.

Finding a lost device has much lower stakes than proving an alibi in court so I see how this model would work.

zed882• 7 years ago

Well...a bit off topic but kind of relevant.

My car got broken into and my iPad nicked. I was able to locate that, however, the cops here in NZ were really unhelpful.

They said the GPS location wouldn't be sufficient for a search warrant as they have had many cases of false positives.

I said I would give the ssid and ip address of their wifi network, even then they wouldn't agree for a raid.

It was only when the thief (who was a minor) took the pic of his family member, which I then furnished to the police (via iCloud), they could do something.

Wondering what good is technology, if the law takes a while to catchup, well at least here in NZ.

dylan604• 7 years ago

It's not just NZ. Police in the US are no better. In the Dallas PD, the detective assigned to the case when our house was burgled would not respond to emails sent to him providing evidence. After reaching out through other avenues to reach the detective, he flat out responded with being too busy to read emails. The case went uncleared. However, a few weeks later, there was a random call saying they found an iPad reported as lost/stolen and would be willing to return it for a small finder's fee. Again, the police refused to assist during the meet up.

m4637• 7 years ago

I've noticed in my lifetime that a number of crimes have become ad-hoc decriminalized.

Smaller crimes like bicycle theft or small electronics are basically "who cares" to the police. Many police departments don't even do bicycle registrations anymore.

Even car theft has sort of fallen to insurance companies to take care of. A lot of people just want a police report to turn in to insurance so they can get a new car.

I don't know about serious crimes. Are people more often caught with lots of data and the erosion of privacy?

mensetmanusman2• 7 years ago

When I get frustrated with the police, it helps to remember that they make like $25/hr or less. In a wealthy suburb I just moved into a few months ago, I learned that a majority of the children of the police are growing up below the poverty line.

The local politicians are apparently very liberal about their views on police (do not support), so they keep the pay as low as possible. All the police have to live outside the community and commute to work the area since it is unaffordable for them to live here.

I’m actually surprised they serve as well as they do under the circumstances.

erikpukinskis• 7 years ago

Legally could you go get it, and in the resulting skirmish perhaps attract the attention of the police?

Is trespassing to retrieve stolen property still trespassing?

zed882• 7 years ago

I am not sure about the local bylaws around trespassing, but the lady on the police helpline categorically asked me to not do it.

It was being pinged in a gang prone area, I wouldn't have done it anyway.

diminoten3• 7 years ago

Could you hire a asset recovery agent to actually do the "retrieving" for you?

sapphire_tomb• 7 years ago

This reminds me of a (probably apocryphal) story a South African friend of mine told me once about the state of policing down there in the late nineties / early noughties.

The story goes that a man wakes up in the middle of the night to the sound of burglars looting his garage. Given the occurences of aggravated robberies in SA at the time, often involving guns, he didn't want to confront the miscreants himself, and so called his local police department.

Apparently since no actual violence had been done at this point, the police-person to whom he was speaking claimed that they had no free units to come and attend, and that they'd send a car round in the morning to collect evidence. At this point the call ended.

The man who was being burgled was understandably unimpressed with this, thought about what he could do, and then rang the police back.

"Don't worry about the burglars here. I shot them." he says.

Within minutes his house is surrounded by police cars, and the burglars are under arrest.

The commander of the responding officers says to the man "I thought you said you shot them?"

The man replies "I thought you said you had no units free?"

jlgaddis• 7 years ago

Ask O.J. Simpson.

bo1024• 7 years ago

I can definitely see the point regarding GPS location, I remember an article about people living at some default coordinates suffering from something like daily or weekly police raids.

m-app2• 7 years ago

Indeed, due to MaxMind's GeoIP location for the middle of the US (when it can't find a more accurate US location) at 38°N 97°W. So unfortunate.

https://splinternews.com/how-an-internet-mapping-glitch-turn...

robk• 7 years ago

Funnily in the UK I got Oxford police to enter a house based on GPS and ssid and me remotely setting a loud alert on the phone. The robber sadly smashed it though while being apprehended.

zone411• 7 years ago

Tile has quite a few patents in this area: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=H...

sebazzz• 7 years ago

Can the signal be jammed? Or simply put the stolen device in a metal box.

As for the tracking: I really like the idea. However, in my country finding your device isn't the issue, it is getting it back that's the problem. Police won't go and enter the particular house were your device is.

ascorbic• 7 years ago

I'm not sure how useful a device is that has to be kept in a metal box at all times.

justwalt• 7 years ago

My new startup: Faraday gloves

antpls• 7 years ago

Nice article, and also nice application of cryptography. I hope Google and Apple will both compete and challenge each others about inventive ways to defend people privacy, both at the hardware and software levels

Skunkleton• 7 years ago

generate the list of pseudonyms from a single short “seed” that both Timmy and Ruth will keep a copy of. This is nice because the data stored by each party will be very small. However, to find Timmy, Ruth must still send all of the pseudonyms — or her “seed” — up to Apple, who will have to search its database for each one.

I would imagine something along the lines of TOTP would provide a better mechanism here. There would be no need to scan a whole list of pseudonyms, and the BLE would rotate the identifier it transmits frequently. The lassie device can include GPS timestamps when it reports the device to apple.

mjlee• 7 years ago

A potential concern - does this system implement forward secrecy? Is that even possible?

The threat I'm thinking of is some organisation that is able to crack the private key at some point in the future and therefore able to work out where you have been in the past.

Of course, the phone's location in the recent past is exactly what this system is designed to produce. Would it be possible to rekey the connection on a regular/opportunistic basis?

shitals• 7 years ago

TLDR; The idea of the new system is to turn Apple’s existing network of iPhones into a massive crowdsourced location tracking system. Every active iPhone will continuously monitor for BLE beacon messages that might be coming from a lost device. When it picks up one of these signals, the participating phone tags the data with its own current GPS location; then it sends the whole package up to Apple’s servers.

graton• 7 years ago

Milwaukee Tools (and possibly others) do something similar. Not sure about the privacy part though.

https://www.milwaukeetool.com/OneKey

Basically anyone who runs the Milwaukee One Key app will watch for signals from tools and other devices with the One Key transmitter and upload the location. So if your tool is stolen and comes within range of someone running the One Key app the location should get uploaded.

snarf212• 7 years ago

Tile meshes the same way.

How does Apple privately find offline devices?

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