Cryptology ePrint Archive: Report 2020/1543

CovidBloc: A Blockchain Powered Exposure Database for Contact Tracing

Deepraj Pandey and Nandini Agrawal and Mahabir Prasad Jhanwar

Abstract: Contact tracing is an important mitigation tool for national health services to fight epidemics such as COVID-19. While many of the existing approaches for automated contact tracing focus on privacy-preserving decentralized solutions, the use of blockchain in these applications is often suggested for the transparency and immutability of the data being collected.

We present CovidBloc, a contact tracing system that implements the COVID 19 exposure database on Hyperledger Fabric Blockchain Network. Like most decentralized contact tracing application, the participants of the CovidBloc are: (1) a mobile application running on a bluetooth-equipped smartphone, (2) a web dashboard for health officials, and (3) a backend server acting as a repository for data being collected. We have implemented all components of CovidBloc to make it a fully functional contact tracing application. It is hosted at

The mobile application for CovidBloc is developed for Android. The exposure notification system in our mobile application is implemented as per the recently released draft documentation by Google and Apple. The exposure notification API from Google and Apple is only available to a limited number of teams per country.

The backend server is an important component of any automated contact tracing system which acts as a repository for exposure data to be pushed by smartphones upon authorization by the health staff. Since adding or removing information on the server has privacy consequences, it is required that the server should not be trusted. The backend server for CovidBloc is implemented on Hyperledger Fabric Blockchain network.

Category / Keywords: implementation / Contact Tracing, Blockchain

Date: received 10 Dec 2020

Contact author: mahavir jhawar at ashoka edu in

Available format(s): PDF | BibTeX Citation

Version: 20201213:163926 (All versions of this report)

Short URL:

[ Cryptology ePrint archive ]