what about the old My-dog-ate-my-sim-card-routine aka ditching your 2fa token ... like i really don';t know because I denied myself access:

"...Then, before you cross the border, make sure you don’t have the SIM card that allows you—or customs officials—to receive that text message, essentially denying yourself the ability to cooperate with agents even if you wanted to. Zdziarski suggests mailing yourself the SIM card, or destroying it and then recovering the accounts with backup codes"

https://www.wired.com/2017/02/guide-getting-past-customs-dig...

Then you will quite possibly be denied access simply because they cannot harvest your social media profiles for profiling.

Kennywinker's comment is right that technological cleverness won't help much here. Carry no devices, and you are suspicious and/or non-cooperative (unless you are over the age of sixty). Carry devices with no data, and you are suspicious and/or non-cooperative. Carry devices with carefully prepared fake profiles and datasets and you might pass muster… or be regarded as suspicious, non-cooperative, and/or actively resisting (if the border agent judging you suspects he is seeing fake data).

I wonder how they are trained to react to people without social media accounts.

> Then you will quite possibly be denied access simply because they cannot harvest your social media profiles for profiling.

Not just because they can't. Because you specifically took steps to prevent them from doing it.

> Because you specifically took steps to prevent them from doing it.

... or I'm travelling with my local SIM to avoid roaming charges?

That only works if you've already been to the US and have a local SIM card.

Also — you left your home country SIM at home because you don't care about the roaming charges back home getting to/returning from the airport?

> you left your home country SIM at home because you don't care about the roaming charges back home getting to/returning from the airport?

Because I don't want to lose it. This is exactly how I've travelled before hearing that this 'handover your passwords' existed.

No roaming charges because it's not being used - I can live without a very functional phone between the WiFi at the airport in my home country, and home.

(Actually, right now I don't even carry the dumbphone that has my SIM it. I'm content with WiFi.)

Do you have any basis for your last point?

I legitimately don't know many of my passwords, there's no legal obligation to know them, and the law generally cant compel you to do impossible things (eg, tell them something you don't know).

They can subpoena my password safe, just like any other file on my computer, and possibly require I unlock it (this is disputed), but I don't see any reason they can demand I reproduce the contents of the safe that I don't know.

While there's no legal obligation to know them, there's no legal obligation for you to be let through the border - for non-citizens crossing USA border, the explicit legal presumption(starting from [1]) is that you're not fulfilling the conditions of the visa and you have to convince the immigration officer that you are entitled to entry. If they want to check certain information that is not available for you (no matter if the reason is good or not) and they are not convinced otherwise that you don't have any risks, then there's no "beyond reasonable doubt" like in criminal proceedings - if they are not convinced that you're not going to e.g. work in USA, then they have not only the right, but a duty to deny you entry.

[1] (b) Every alien 10/ (other than a nonimmigrant described in subparagraph (L) or (V) of section 101(a)(15), and other than a nonimmigrant described in any provision of section 101(a)(15)(H)(i) except subclause (b1) of such section) shall be presumed to be an immigrant until he establishes to the satisfaction of the consular officer, at the time of application for a visa, and the immigration officers, at the time of application for admission, that he is entitled to a nonimmigrant status under section 101(a)(15) .

If you say you can't remember your password, they can't force you to remember, but they can tell you to go home.

When you're a foreigner attempting to enter the USA, they can simply deny you entry for failing to do what they want. US CBP has the authority to make arbitrary decisions not to admit foreigners, and CBP faces almost no scrutiny.

Most other countries give their border guards similar authority with respect to foreigners not entitled to enter by some treaty (e.g. EU).

First, IANAL, and I am not an expert for the situation in the US. So you're probably right.

But in the UK, you can go to jail for not disclosing your cryptographic keys. https://en.wikipedia.org/wiki/Key_disclosure_law#United_King...

Here is a story of a person who went to jail for not disclosing his keys: http://www.theregister.co.uk/2009/11/24/ripa_jfl/?page=1 He said he kept silent "because of principle", but I guess he might also have gone to jail if he told them "I don't remember" - Officers would not believe him anyway.

The prosecution has to show that you know the keys to convict you under that law.

Even in the UK the two situations are different. In the cases you cited, not surrendering passwords is considered to be contempt of court. At a border, you might be denied entry, which is bad, but that's it.

The law only exists to the extent that it is enforced. If customs says "give us your passwords or you're not coming through" and you don't have a lawyer handy, then "give us your passwords or you're not coming through" is now the law (until a judge overturns it and possibly charges the officer for breaking another law).

If you can call a lawyer and don't mind waiting several hours, you can challenge it. However most people don't have a lawyer and don't know what to do and are afraid of the officers.

And also, noncitizens do not have a right to contact a lawyer when they are detained at an airport.

If you call a lawyer in such a situation, they'll tell you that Customs has 100% discretion to admit or deny non-citizens and there is no such thing as "challenging" it.