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Comment by cbsks | Hacker News Reader

“GrayKey also allows agencies to install the agent which surreptitiously records the user's passcode if authorities hand their phone back to them”

Yikes. This is something that probably would trip up a lot of people. After arresting you and taking your phone, they say you can make a phone call and pass your phone back to you. You unlock and it’s game over.

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(Sorry for the offtopicness but could you please email me at hn@ycombinator.com? I want to send you some repost invites and this is the only way to get in touch!)

Good to know though - if you are ever arrested, reboot your iPhone before entering the PIN. At least for the last 5 years since (I believe) the A9, no malware or jailbreak has managed to be persistent on an iPhone beyond a reboot that we know of.

This is likely because all of the exploits jailbreaks or malware use are flaws in already running processes, but when the phone is rebooted, hardware root of trust verifies everything that loads is signed by Apple, clearing out the virus/jailbreak unless it was manually invoked (or plugged into the GrayKey) again to re-exploit those processes.

Of course, in the unlikely event that you happened to have an iPhone without the new Secure Storage component mentioned on this thread, be arrested, and the cops were trying to "Hide UI" on you, it would be really awkward for them if you rebooted your phone first ruining the trap. "Wait, no, you're supposed to enter your PIN right now!"

>Good to know though - if you are ever arrested, reboot your iPhone before entering the PIN.

how do you trust that the phone was actually rebooted? ie. the ui fakes a reboot screen.

There is always that risk. However, if you are this paranoid, you need to remember that you can do a Force Restart. This is handled by hardware, not by software, so if you know what to look for it cannot be faked.

https://support.apple.com/guide/iphone/force-restart-iphone-...

Do iPhones have the hard-reset like Android where you hold power for a while, ignoring the on-screen prompts until it's forcefully reset?

That might be an option. If it's not, I guess it's much easier on iOS to fake a reboot as the boot process (visually) is known, on Android it could be anything because it's manufacturer customisable.

EDIT: Fixed some grammar.

Yes, they do.

To fake reboot UI it would need to root the OS. A tremendous and very unlikely achievement.

Incorrect. When the person press and holds the power button, just show a fake graphic onscreen for "swipe to turn off". When person does that, show a black screen for 3 seconds, show the Apple logo for 8 seconds, do an animation, and the phone hasn't rebooted while the person's been tricked.

You can't even trust that it's your phone; it wouldn't be that hard in many cases to provide an identical-looking device that just records the entered PIN. It won't hold up to inspection once unlocked, but it doesn't have to; once you've provided the PIN, you've lost.

If the device has left your possession, don't accept it back or interact with it. Get a new device, and restore it from backup.

Also, if you fill out the emergency contacts in your phone, you can call those contacts without unlocking your phone.

There's an easy defense against this: when you're handed the phone, intentionally enter a passcode that isn't yours. If it unlocks, then you'll immediately know it isn't your phone, and won't have given away your passcode.

If it doesn't unlock, it's probably your phone.

Use siri to dial without unlocking.

Siri has had vulns before that allow device access from the lockscreen. Best to disable it entirely if this is your threat model.

Fortunately, the crack in my screen is quite uniquely identifiable :)

Not sure this matters. Is your screen incompatible with other iPhones?

Just remove the battery.

Oh wait we can't do that anymore.

let the battery die, sure fire way to make the phone reboot, ironically the agent installed on the phone would probably help with this.

You'd probably have to wait days/weeks just to be sure. Otherwise the UI can "pretend" to have a dead battery.

Doesn't that require the device to have been unlocked in the first place?

A device can be compromised while the encrypted user data volume is still locked.

They have to load it before first unlock by definition, and at this point I don't believe that it would be possible to establish persistence. Restart your phone when it's handed back to you by people you don't trust.

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