... but anyway .... could they make their phones totally secure? YES.
Actually, no. To make something "totally secure", it would have to be void of any and all outside influence other then the person handling the device, that includes the kernel/OS and everything on it. This is clearly not possible and not done by anyone so no. There are "semi" secure things such as agencies making their own soft/applications, but they're still open to the agency itself that created that same soft.
You can encrypt all day long, once you "install" something/anything you can get fucked. Did you code your OS? No. Well then you're not 100% secure. This will never change, it's impossible to have something 100% secure.
And cryptography was never about things being reversible. They're called "hashes" for a reason. They're not meant to be reversible. Long gone are the days of things being reversible. And long gone are the researcher focusing on the reversibility. It's by accident mostly that collisions are found in hashes.
ya, post's old, i have nothing to write about and jordan never spoke here. Where are thou?