Making your phone safe for US travel?

RedPanda

In a case where you're currently or in the near future travelling to the US, what would you need to do to make a phone running GrapheneOS safe?

Would deleted apps and accounts within those be unrecoverable or can authorities still read find those?
Is it even possible for authorities to have trojans and spyware that are able to function on GrapheneOS? Is there anything you can do to secure your phone or hide any personal data from prying eyes?

Or is simply getting a burner phone without any kind of social media or other personal accounts or messaging services on it the better advice? Would a regular phone or laptop in your luggage be checked and possibly infected too?

GrouchyGrape

RedPanda I'm not sure you need to do anything really. I know several people that regularly travel from various European countries to the US and they've never been stopped or checked.

That being said, regardless of where you are, if you're stopped and they want to "scan" you're phone, I would be reading the laws of that country. There's a near zero probability they will have an exploit for GOS and even closer to zero probability they would use it on you. I would be more concerned with whether or not they can legally require your password/fingerprint.

RedPanda

GrouchyGrape

The main issue is not legality, but that they can do this whether it's legal or not.
Especially recently they have detained tourists for weeks just because they had issues with their visas or similar stuff.
I would not put it past them to detain and deport you over refusing to let them see your phone. Just like being stupid enough to answer yes to "Are you a communist" on the terminals will probably get you detained.

JollyRancher

Define "safe".

If you are not a US Citizen or, maybe, a legal permanent resident then you must provide unlocked access to your electronic devices at the border upon request or be denied entry to the US.

A US Citizen can refuse but the government will then seize your device and you won't be getting it back short of (maybe) a very expensive lawsuit.

The odds that the US will attempt to search your electronics "randomly" are incredibly low but, again, refusal to cooperate is likely to get you permanently flagged for enhanced scrutiny on any attempt to enter the US, your device permanently seized, and you denied entry on that visit.

If you already might be a person of interest to US authorities then the odds of an attempted search skyrocket.

Use a clean, disposable, phone when crossing the border. Upon entry to the US buy a Pixel, put GOS on it, and then use encrypted cloud backups to reestablish whatever data you need while in the US. That is about the only way to guarantee (in so far as one practically can) safety.