Schneier et. al.'s Keys Under Dormats paper tackles that problem from many angles. You might find it interesting. https://www.schneier.com/academic/paperfiles/

Schneier et. al.'s Keys Under Dormats paper tackles that problem from many angles. You might find it interesting. https://www.schneier.com/academic/paperfiles/paper-keys-under-doormats-CSAIL.pdf https://www.schneier.com/academic/paperfiles/paper-keys-unde...