Hacker News Reader

Comment by Jtsummers | Hacker News Reader

It's the faraday box part in particular. Airplane mode isn't a true no-radios mode on iPhone (this is well-known, or should be on HN at least). But it does leave cellular radios off. Wifi and bluetooth might need to be separately disabled and with wifi, at least, it'll turn back on after a while. So maybe (being very generous), if bluetooth or wifi is enabled or becomes re-enabled, there's a signal between the iPhones that causes this reboot behavior.

But how is a device in a faraday box receiving this signal and rebooting? And why do they need a signal when they could just use their own clocks and determine that it's been X days or weeks since last going online and reboot?

View on HN

> how is a device in a faraday box receiving this signal and rebooting?

Doesn’t need to. Being in a Faraday box is a reasonable trigger for a single reboot. That said, the most incredulous part of this story is that iPhones can detect when they’re in a Faraday cage.

But the claim is that other iPhones in the area are triggering the reboot. Setting that claim aside, though, how would the device even tell it's in a faraday box versus just out in the woods?

> the claim is that other iPhones in the area are triggering the reboot

Lack of motion? The information the other phones provide are proximity (it’s unusual for people to pile their phones together), that the radios still work and possibly a timeline, e.g. if the other phone says “I’ve been in a suspicious state for two days,” the first phone can change its priors.

I could easily see this as a security measure. Give the phone a concept of fear of being stolen. Phone, alone, continued source of power for an extended period. Somebody could have left it on a charger and gone away. Phone, continued source of power for an extended period and static bluetooth signals from other phones--what's going on here? This is very suspicious, turn defenses to max. It doesn't need to know the difference between thieves trying to thwart it and cops trying to thwart it.

environmental RF in the woods, vs band specific shielding in farady cage.

Out there in the woods there's still GPS data. There are very few places on Earth outside a faraday cage where you can go for a long time without receiving *anything*.

I'm going to go ahead and assert that they can't tell. A Faraday cage is just a deliberate construction of a situation that happens all the time anyway. Hospitals have lots of shielded rooms in and around the radiology department. The basement of a steel building is basically the same. So is anywhere on a ship. My aged house has lath and plaster walls that can simultaneously survive a nuclear blast and also block Wi-Fi unless the amp's turned up to 11. There's no sensor in an iPhone that could tell that it's in a specially-constructed Faraday cage instead of a plain old dresser drawer in my bedroom.

Could the phone detect that they are in a small conductive box: stronger interference back when they send a signal?

I'm not sure if that's possible. What's the difference between that and someone sitting their phone on a metal cabinet?

I'm even more confident that Apple hasn't spent the research hours required to do that reliably, then incorporate the electronics and software needed into off-the-shelf phones, all to protect criminals from having their phones hacked under very specific conditions. That seems like a huge money sink.

> What's the difference between that and someone sitting their phone on a metal cabinet?

In a zero-signal environment? With other iPhones in very close proximity?

You can even measure your false positive rate by timing to first successful unlock. If it happens more than once, turn down the sensitivity on the feature (or turn it off completely).

(Were I designing this feature, I’d let phones in this state poll the other phones on how long they’ve been in it.)

Ultrasound?

Reply on news.ycombinator.com