DIMY: Enabling Privacy-preserving Contact Tracing

TL;DR

DIMY is a blockchain-based contact tracing protocol that ensures full privacy protection for users' data throughout the contact tracing process, addressing privacy concerns of existing solutions.

Contribution

It introduces a novel privacy-preserving contact tracing protocol using blockchain, Bloom filters, and Diffie-Hellman key exchange, with improved privacy and efficiency.

Findings

Resilience against common attacks

Lower storage overhead compared to existing apps

Negligible computational overhead

Abstract

The infection rate of COVID-19 and lack of an approved vaccine has forced governments and health authorities to adopt lockdowns, increased testing, and contact tracing to reduce the spread of the virus. Digital contact tracing has become a supplement to the traditional manual contact tracing process. However, although there have been a number of digital contact tracing apps proposed and deployed, these have not been widely adopted owing to apprehensions surrounding privacy and security. In this paper, we propose a blockchain-based privacy-preserving contact tracing protocol, "Did I Meet You" (DIMY), that provides full-lifecycle data privacy protection on the devices themselves as well as on the back-end servers, to address most of the privacy concerns associated with existing protocols. We have employed Bloom filters to provide efficient privacy-preserving storage, and have used the Diffie-Hellman key exchange for secret sharing among the participants. We show that DIMY provides resilience against many well known attacks while introducing negligible overheads. DIMY's footprint on the storage space of clients' devices and back-end servers is also significantly lower than other similar state of the art apps.