2019-01-11 Privacy-preserving ridesharing and multi key-homomorphic signatures

Abstract

In this talk, Pagnin will presen present two recent works:

TOPPool (under submission): Ridesharing is revolutionizing the transportation industry in many countries. Yet the state of the art is based on heavily centralized services and platforms, where the service providers have full possession of the users’ location data. Recently, researchers have started addressing the challenge of enabling privacy-preserving ridesharing. The initial proposals, however, have short- comings, as some rely on a central party, some give up precision, some incur high performance penalties, and most do not consider time preferences for ridesharing. This paper presents TOPPool, a time-aware, optimized approach to privacy-preserving ridesharing. We show that TOPPool preserves privacy without relying on a third party or sacrificing precision, while it is also superior in performance over the preceding work. We evaluate the approach on real-world data from New York’s Taxi & Limousine Commission. 

Matrioska (SCN 18): Multi-Key Homomorphic Signatures (MK-HS) enable clients in a system to sign and upload messages to an untrusted server. At any later point in time, the server can perform a computation C on data provided by t different clients, and return the output y and a short signature σC,y vouching for the correctness of y as the output of the function C on the signed data. In this paper, we investigate connections between single-key and multi-key homomorphic signatures. We propose a generic compiler, called Matrioska, which turns any (sufficiently expressive) single-key homomorphic signature scheme into a multi-key scheme. Matrioska establishes a formal connection between these two primitives and is the first alternative to the only known con- struction under standard falsifiable assumptions. Our result relies on a novel technique that exploits the homomorphic property of a single-key HS scheme to compress an arbitrary number of signatures from t different users into only t signatures.

About Elena Pagnin

Elena Pagnin received a master degree in applied mathematics at the University of Trento in 2013 with a thesis on "homomorphic authentication codes". The thesis contains her research work carried out as a project officer at Nanyang Technological University (Singapore). Elena defended her doctoral thesis on "enhancing data and user authentication in collaborative settings” in September 2018 at the computer science and engineering department of Chalmers University of Technology. Elena’s research focuses on cryptographic primitives for data and user authentication. Her main interests are on homomorphic tools in cryptography and security of asynchronous messaging (e.g., the Signal protocol). For further details visit Elena Pagnin's webpage at Chalmers .