.mat files don't have the option for password protection. You could encrypt them I suppose, making them unusable as .mat files without the reverse operation. But then you would need to have your code protected and made unreadable too.
Perhaps better could be to write your own files, encrypted in your own proprietary format so they would be unreadable, at least not without the correct code. Then use pcode to protect the reading tools, so the reader cannot be used by others. It will be tough to do, since even pcode can apparently be hacked by the determined hacker.
Or you might store the files in a secure location in the cloud, inaccessible without the proper permissions.
