5 ms·

Ackhually, it is that hard, unless your method relies on millions of your devices out in the wild acting as sensors in a mesh network, as Apple does.

amluto 2y ago
That’s a much harder problem than VW would need to solve. Also, Find My substantially predates the Find My network and AirTags. There are very straightforward solutions, depending on the threat model. For example, the app could send VW a private key every day, and VW would send that key to the car. Then the car sends periodic location reports, encrypted to that key. VW can, upon request, send the report to the app, which decrypts it. But VW can’t decrypt the report itself, so they don’t know the location of the car. Also, it’s forward secure in the sense that a leak of VW’s database is entirely useless after a day.
- magicalhippo 2y ago
  This would require a key per app installation, my SO has the app installed too for example. It would also introduce a lot of additional failure modes. Doable but not exactly trivial.
  - layer8 2y ago
    It would work exactly like how you can send an encrypted email to multiple recipients and each of them can decrypt it despite having different private keys. That part isn’t rocket science.
    - magicalhippo 2y ago
      Indeed, it's making it work reliably and with zero friction given both apps and car will have variable internet access.
      - amluto 2y ago
        This is not hard. App login sets up a session with VW (which is surely already does), except the session needs a database entry and not just a JWT-like token. (Many auth frameworks do this anyway.) The database row needs to add a public key, and the server needs to send all the key changes to the car. And that’s about it.
        magicalhippo 2y ago
        Again, that's the easy part. The hard part is making it work reliably in the real world.
        deleted 2y ago
        [deleted]
        amluto 2y ago
        What, exactly, makes it hard to get this to work reliably in the real world? The app already won’t work without a valid login session. The car is already sending a little blob of data to the mothership containing a location. If the communication to the mothership changes to having the mothership send a list of keys and the car encrypt its blob, that’s basically it. The total increase in communication needed is one round trip to revalidate keys. I realize that modern development has layers and layers of documents and teams and overcomplicated interfaces, but this is the kind of thing that could be done by one developer, using two servers and a load balancer (or a more creative HA scheme with client assistance that can easily survive complete loss of a datacenter or two), that can handle the entire fleet.
        magicalhippo 2y ago
        The app and car will have intermittent connection to the internet. My car for example doesn't have reliable connection when it's parked in the garage, which is where I charge it. Your solution would add a lot of extra edge cases that needs to be considered. You have to ensure the updated key is reliably transferred to the mothership in a timely fashion, and subsequently that the key is reliably transferred to the car in a timely fashion. That's the back-end stuff. There's also the front-end stuff, like will my SO understand why her app isn't showing the car's location but mine is? Not saying it's impossible, but it adds a lot of complexity beyond simply encrypting the location with multiple keys.
- deleted 2y ago
  [deleted]
- layer8 2y ago
  You cannot establish a private channel between app and car if you don’t already have either a pre-shared secret, or pre-shared trusted certification authority keys (such as to allow TLS-like tamper-resistant encrypted communication between app and car) that VW can’t replace. Otherwise, if there is no pre-existing private channel, the key (which by the way would have to be the public key, not the private key) could be switched out by VW acting as a man-in-the-middle, allowing it to access all encrypted content going through it. The same is true for Apple. There are parts of the protocol or the pairing where you have to trust Apple, either their servers, or if the establishment happens locally via bluetooth or similar, their software that runs on the local devices.
  - amluto 2y ago
    This argument seems like a fairly extreme example of the perfect being the enemy of the good. Sure, it would require a more advanced system for VW to prevent themselves from silently compromising their own system to learn everyone’s location. But the design I outlined will prevent a passive compromise of VW, and even possibly a court order, from learned everyone’s location, and it prevents even an active and highly malicious compromise from learning past locations.
    - layer8 2y ago
      I was triggered by the argument “Apple knows how to allow one to find one’s devices without Apple knowing where they are. It’s not that hard.” People misunderstand this as Apple having no possibility to learn the location if they wanted to. And that’s just not the case.
      - amluto 2y ago
        Of course Apple could do this. But Apple is the one major company that actually goes out of its way not to.
    - mulmen 2y ago
      "Shipping the private key" does not meet the bar for "good". You still need a way to establish trust in your key distribution and also implement the system correctly. The proper way to secure access to a physical thing you own is to only communicate directly with that thing.

amluto 2y ago

That’s a much harder problem than VW would need to solve. Also, Find My substantially predates the Find My network and AirTags. There are very straightforward solutions, depending on the threat model. For example, the app could send VW a private key every day, and VW would send that key to the car. Then the car sends periodic location reports, encrypted to that key. VW can, upon request, send the report to the app, which decrypts it. But VW can’t decrypt the report itself, so they don’t know the location of the car. Also, it’s forward secure in the sense that a leak of VW’s database is entirely useless after a day.

magicalhippo 2y ago
This would require a key per app installation, my SO has the app installed too for example. It would also introduce a lot of additional failure modes. Doable but not exactly trivial.
- layer8 2y ago
  It would work exactly like how you can send an encrypted email to multiple recipients and each of them can decrypt it despite having different private keys. That part isn’t rocket science.
  - magicalhippo 2y ago
    Indeed, it's making it work reliably and with zero friction given both apps and car will have variable internet access.
    - amluto 2y ago
      This is not hard. App login sets up a session with VW (which is surely already does), except the session needs a database entry and not just a JWT-like token. (Many auth frameworks do this anyway.) The database row needs to add a public key, and the server needs to send all the key changes to the car. And that’s about it.
      - magicalhippo 2y ago
        Again, that's the easy part. The hard part is making it work reliably in the real world.
        deleted 2y ago
        [deleted]
        amluto 2y ago
        What, exactly, makes it hard to get this to work reliably in the real world? The app already won’t work without a valid login session. The car is already sending a little blob of data to the mothership containing a location. If the communication to the mothership changes to having the mothership send a list of keys and the car encrypt its blob, that’s basically it. The total increase in communication needed is one round trip to revalidate keys. I realize that modern development has layers and layers of documents and teams and overcomplicated interfaces, but this is the kind of thing that could be done by one developer, using two servers and a load balancer (or a more creative HA scheme with client assistance that can easily survive complete loss of a datacenter or two), that can handle the entire fleet.
        magicalhippo 2y ago
        The app and car will have intermittent connection to the internet. My car for example doesn't have reliable connection when it's parked in the garage, which is where I charge it. Your solution would add a lot of extra edge cases that needs to be considered. You have to ensure the updated key is reliably transferred to the mothership in a timely fashion, and subsequently that the key is reliably transferred to the car in a timely fashion. That's the back-end stuff. There's also the front-end stuff, like will my SO understand why her app isn't showing the car's location but mine is? Not saying it's impossible, but it adds a lot of complexity beyond simply encrypting the location with multiple keys.
deleted 2y ago
[deleted]
layer8 2y ago
You cannot establish a private channel between app and car if you don’t already have either a pre-shared secret, or pre-shared trusted certification authority keys (such as to allow TLS-like tamper-resistant encrypted communication between app and car) that VW can’t replace. Otherwise, if there is no pre-existing private channel, the key (which by the way would have to be the public key, not the private key) could be switched out by VW acting as a man-in-the-middle, allowing it to access all encrypted content going through it. The same is true for Apple. There are parts of the protocol or the pairing where you have to trust Apple, either their servers, or if the establishment happens locally via bluetooth or similar, their software that runs on the local devices.
- amluto 2y ago
  This argument seems like a fairly extreme example of the perfect being the enemy of the good. Sure, it would require a more advanced system for VW to prevent themselves from silently compromising their own system to learn everyone’s location. But the design I outlined will prevent a passive compromise of VW, and even possibly a court order, from learned everyone’s location, and it prevents even an active and highly malicious compromise from learning past locations.
  - layer8 2y ago
    I was triggered by the argument “Apple knows how to allow one to find one’s devices without Apple knowing where they are. It’s not that hard.” People misunderstand this as Apple having no possibility to learn the location if they wanted to. And that’s just not the case.
    - amluto 2y ago
      Of course Apple could do this. But Apple is the one major company that actually goes out of its way not to.
  - mulmen 2y ago
    "Shipping the private key" does not meet the bar for "good". You still need a way to establish trust in your key distribution and also implement the system correctly. The proper way to secure access to a physical thing you own is to only communicate directly with that thing.