This is especially true if you allow them to frame the action as "hiding". L
First you must ask them to not use loaded terminology like "hiding" when dealing with information you own and don't feel like accessing. Don't answer "yes" or "no" to whether you're hiding something. If you use their words then they have a huge advantage.
I'm gonna bet that trying to "language-lawyer" how your CBP agent phrases their questions is a one-way ticket to a private interview, because that's not suspicious at all.
You don't have to explain yourself to them. They don't know the legalities involved, they are grunts. Just tell them simply that you will only answer the question a single time, and the answer is no, and you will ignore future questions about the matter. And ask for your lawyer. If you aren't going to allow access into your personal devices to begin with, you're probably getting that interview regardless.
First you must ask them to not use loaded terminology like "hiding" when dealing with information you own and don't feel like accessing. Don't answer "yes" or "no" to whether you're hiding something. If you use their words then they have a huge advantage.