In theory , for phones with cortex-a15 cpu, one could use ARMORED[1] , which encrypts the content of ram, with keys saved outside the reach of the baseband, ins

In theory , for phones with cortex-a15 cpu, one could use ARMORED[1] , which encrypts the content of ram, with keys saved outside the reach of the baseband, inside registers. But still, CPU backdoors are possibility. [1]http://www1.informatik.uni-erlangen.de/filepool/projects/armored/armored.paper.pdf http://www1.informatik.uni-erlangen.de/filepool/projects/arm...