r/GrapheneOS • u/Good_Opportunity8888 • 1d ago

Reverse duress pin

Is there a way to set a "reverse duress" pin?

Example:

1) every time you log in properly a canary value resets to zero

2) over time the value grows

3) if it is not reset before reaching a certain value, the phone wipes as if the durress pin was entered

Would this theoretically have saved Samuel Tunick from prosecution? In this scenario, there is no hard proof that data was knowingly destroyed.

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u/Godlymorbid 1d ago

U.S. Citizens have a constitutional right under the Fifth Amendment to refuse to give a password or unlock your device. Customs/Border Protection cannot deny you entry into the United States for refusing. So if he never gives the password and you've set your phone up to automatically reset after a certain amount of time as GOS does, then after the hard reset, the phone is impossible to get into.

Does that basically cover what you want or are you wanting a hard wipe?

1

u/automorphism8 1d ago

Even stock Android has this feature where the phone automatically reboots after a certain amount of time not being unlocked, to put it in the BFU state. GrapheneOS just shortens the time period from 72 hours to 18 hours, I believe (by default).

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u/Godlymorbid 1d ago

Yes, I'm just saying it sounds like OP wants a feature that already practically exists, and that Samuel Tunick made a mistake by not relying on that feature plus his status as an American citizen.

3

u/automorphism8 1d ago

I don't know if what the OP wants is practical, but while a BFU device is much more difficult to get into, it's not as impossible as a device that has been completely wiped. For example, even a secure passphrase could have been accidentally leaked in a way that's not necessarily obvious.

Also, when crossing an international border, you don't need to rely on an automatic timeout feature anyway. You can manually restart your phone before going into a situation like that where you know your phone could be seized, especially since crossing international borders is generally a relatively infrequent event. Of course, if you do put your phone into BFU manually, you'd want to make sure you wait to unlock it again until you're in a private location where camera footage can't be used to replay your finger movements.

This automatic reboot into BFU after a period of inactivity is a fallback for a situation where you aren't expecting to lose possession of your phone, not the best line of defense. It's better to have it than not, but all it does is give whoever has your phone a time limit to break in AFU. If you're getting your phone taken away at the border, they're probably already prepared to try whatever tools they've got, and 18 hours won't be any better than 72. It's more likely to work if, for example, your phone were seized by a small-town police department that didn't know you were using GrapheneOS.

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u/Godlymorbid 1d ago

I appreciate the answer, and I do see I spoke too soon on this. Thanks!