And now The Register <http://www.theregister.co.uk/2017/02/14/reg_guide_to_data_security_when_entering_us/> has chimed in with some tips: If you are coming in on a green card, visa or a visa-waiver, you technically don't have to give up passwords or encryption keys. However, the CBP doesn't have to let you into the country if you refuse – it's up to the discretion of the CBP officer at the time. If you are refused entry, you'll be put in a holding cell and sent home. If you're lucky, the airline will let you change your return ticket – if not you'll have to pay for another one. Being ejected will show up as a big red flag next time you try to enter the US. ... "If, by happenstance, you've set up your security so that you cannot access what they need yourself, this in my opinion is far better than simply telling someone that you don't have a social media account. 'My Twitter account only works from my home computer' is an honest and accurate response, and much better than getting caught in a lie later on about not having a social media account." Above all, don't panic. If you appear vaguely Middle Eastern or have a Middle Eastern name, expect some questioning at the border, and prepare your devices for seizure.