If the governments claim they have authority to search your phone, then the only solution is not to store things on your phone during those border activities. Any system for denial of access will simply be considered obstruction.
So technical solutions would simply be to have a backup somewhere, with no trace of the backup software on the device itself. Get to where you're going, go to the website, or download the app, or plug it into another computer, and restore your data from the internet via access codes you have memorized. Or simply travel with a device dedicated for travel, and not your personal goings on.
But obviously, technical solutions don't solve the root poison, which is government destruction of rights and social health in the name of "protecting our rights and society from terrorists".
So technical solutions would simply be to have a backup somewhere, with no trace of the backup software on the device itself. Get to where you're going, go to the website, or download the app, or plug it into another computer, and restore your data from the internet via access codes you have memorized. Or simply travel with a device dedicated for travel, and not your personal goings on.
But obviously, technical solutions don't solve the root poison, which is government destruction of rights and social health in the name of "protecting our rights and society from terrorists".