Electronic Frontier Foundation
Powering off your phone or laptop erases the key that unlocks its encryption, and so protects against unwanted searches, EFF’s Will Greenberg told AP. “This is why a border agent can’t simply turn a device on to use a tool like Cellebrite.” https://apnews.com/article/internet-privacy-smartphones-travel-e0a3146ae7966ea0e4157dbfae1f6a81
One Tech Tip: Locking down your device when crossing borders

Travelers should prepare for extra scrutiny of devices when crossing borders, especially when entering the U.S. Experts say 100% privacy might be impossible but there things you can do to make it harder for someone to see your private data. If possible, leave your phone at home. If you need one, you could get a temporary device with just the information needed for your trip. If you have to bring your phone or laptop, store any sensitive information in a cloud storage service and then delete it from the device. Power off your phone when you get to the border. Turn off biometrics and used PINs and passcodes instead.

AP News
Apr 10, 2025 at 10:03pmWeb
Show threadJoe CotelleseApr 10, 2025
@eff and if you have an iOS device, you can use Siri to quickly shut down your phone if you need to.
Show threadOrca 🌻 | 🎀 | 🪁 | 🏴🏳️‍⚧️Apr 11, 2025
@eff It's possible for tools like Cellebrite to exploit BFU vulnerabilities if the phone is powered off or powered on but before first unlock, those vulnerabilities are harder to find, but not unseen.
Show threadFrank CasaApr 11, 2025
Most countries these days throw out your rights as soon as you get near the border.