Sacha Servan-Schreiber

2papers

2 Papers

CRDec 11, 2019
Judge, Jury & Encryptioner: Exceptional Device Access with a Social Cost

Sacha Servan-Schreiber, Archer Wheeler

We present Judge, Jury and Encryptioner (JJE) an exceptional access scheme for unlocking devices that does not give unilateral power to any single authority. JJE achieves this by placing final approval to unlock a device in the hands of peer devices. 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 recently active peer devices that must be physically located by law enforcement in order to gain access to the locked device. This requires that law enforcement expend both human and monetary resources and pay a "social cost" in order to find and request the participation of random device owners in the unlock process. Compared to other proposed exceptional access schemes, we believe that JJE mitigates the risk of mass surveillance, law enforcement abuse, and vulnerability to unlawful attackers. While we propose a concrete construction, our primary goal with JJE is to spur discussion on ethical exceptional access schemes that balance privacy of individuals and the desires for law enforcement. JJE transparently reveals the use of exceptional access to the public and enforces a fixed social cost that, we believe, can be an effective deterrent to mass surveillance and abuse.

CRJan 19, 2019
STAR: Statistical Tests with Auditable Results

Sacha Servan-Schreiber, Olga Ohrimenko, Tim Kraska et al.

We present STAR: a novel system aimed at solving the complex issue of "p-hacking" and false discoveries in scientific studies. STAR provides a concrete way for ensuring the application of false discovery control procedures in hypothesis testing, using mathematically provable guarantees, with the goal of reducing the risk of data dredging. STAR generates an efficiently auditable certificate which attests to the validity of each statistical test performed on a dataset. STAR achieves this by using several cryptographic techniques which are combined specifically for this purpose. Under-the-hood, STAR uses a decentralized set of authorities (e.g., research institutions), secure computation techniques, and an append-only ledger which together enable auditing of scientific claims by 3rd parties and matches real world trust assumptions. We implement and evaluate a construction of STAR using the Microsoft SEAL encryption library and SPDZ multi-party computation protocol. Our experimental evaluation demonstrates the practicality of STAR in multiple real world scenarios as a system for certifying scientific discoveries in a tamper-proof way.