This is a lost cause. root can always read system memory anyway (even w/o a core dump). If you do not trust root on the system, don't use that system for this. If you do trust root, set your umask to 077.
The intelligent reader will judge for himself. Without examining the facts fully and fairly, there is no way of knowing whether vox populi is really vox dei, or merely vox asinorum. -- Cyrus H. Gordon