Depending on country laws, refusing to reveal keys or even device-level encryption itself may be illegal/cause you to be detained.
The best thing you can do is bring a wiped device through, and assume that it and its data can be seized at any time. Also treat any device as disposable - once seized, it should not be trusted.
The best thing you can do is bring a wiped device through, and assume that it and its data can be seized at any time. Also treat any device as disposable - once seized, it should not be trusted.