The increasing deployment of end-to-end encrypted communications services has ignited a
debate between technology firms and law enforcement agencies over the need for lawful
access to encrypted communications. Unfortunately, existing solutions to this problem suffer
from serious technical risks, such as the possibility of operator abuse and theft of escrow key
material. In this work we investigate the problem of constructing law enforcement access
systems that mitigate the possibility of unauthorized surveillance. We first define a set of …