Differential privacy in tripartite interaction: A case study with linguistic minorities in Canada

Abstract

This paper relates our venture to solve a real-world problem about official language minorities in Canada. The goal was to enable a form of linkage between health data (hosted at ICES - a provincial agency) and language data from the 2006 census (hosted at Statistics Canada - a federal agency) despite a seemingly impossible set of legal constraints. The long-term goal for health researchers is to understand health data according to the linguistic variable, shown to be a health determinant. We first suggested a pattern of tripartite interaction that, by design, prevents collection of residual information by a potential adversary. The suggestion was quickly set aside by Statistics Canada based on the risk of collusion an adversary could exploit among these entities. Our second suggestion was more involved; it consisted in adapting differential privacy mechanisms to the tripartite scheme so as to control the level of leakage in case of collusion. While not being rejected and even receiving enthousiastic interest per se, the solution was considered an option only if other simpler (but also less promising) alternatives are first, and methodically ruled out. © 2013 Springer-Verlag.