https://cseweb.ucsd.edu/~savage/papers/lawful.pdf
Lawful Device Access without Mass Surveillance Risk:A Technical Design Discussion
> This paper proposes a systems-oriented design for supporting court-ordered data access to “locked” devices with system-encrypted storage, while explicitly resisting large-scale surveillance use. We describe a design that focuses entirely on passcode self-escrow(i.e., storing a copy of the user passcode into a write-only component on the device) and thus does not require any changes to underlying cryptographic algorithms. Further, by predicating any lawful access on extended-duration physical seizure, we foreclose mass-surveillance use cases while still supporting reasonable investigatory interests. Moreover, by couching per-device authorization protocols with the device manufacturer, this design avoids creating new trusted authorities or organizations while providing particularity (i.e., no “master keys” exist). Finally, by providing a concrete description of one such approach, we hope to encourage further technical consideration of the possibilities and limitations of trade-offs in this design space.
Judge, Jury & Encryptioner: Exceptional Access with a Fixed Social Cost
https://arxiv.org/abs/1912.05620
> We present Judge, Jury and Encryptioner (JJE) an exceptional access scheme for unlocking devices that does not give unilateral power to any single authority and places final approval to unlock in the hands of peer devices. Our scheme, JJE, distributes maintenance of the protocol across a network of "custodians" such as courts, government agencies, civil rights watchdogs and academic institutions. Unlock requests, however, can only be approved by a randomly selected set of unlock delegates, consisting of other peer devices that must be physically located to gain access. This requires that law enforcement expend both human and monetary resources and pay a "fixed social cost" in order to find and request the participation of law abiding citizens in the unlock process.