Paper 2022/209

Blockchain based Contact Tracing: A Solution using Bluetooth and Sound Waves for Proximity Detection

ZiXi Hee and Iftekhar Salam

Abstract

In the wake of the Covid-19 pandemic, countries and organizations started looking towards technology to curb the spread of the disease, for instance, conducting contact tracing with smartphones. Many contact tracing applications are on the market, built on different technology, such as Bluetooth, GPS, Sound, and QR code scanning systems. The use of sound is an area that has potential for further exploration; currently, only NOVID is utilizing this technology. On top of that, there is a need for a decentralized backend solution that is both public and auditable to address data manipulation concerns. One of the possible solutions is using a blockchain as the backend for the system. We propose a blockchain-based contact tracing solution that uses sound and Bluetooth to detect proximity. Our proposed solution uses blockchain as the backend of the system for decentralized storage of contact tracing data. In the proposed system, close contact is established if both Bluetooth and sound are detected between the communicating devices. The practicality of the proposed scheme is assessed by a performance evaluation of the proximity detection system and a proof-of-concept of the blockchain backend. The results show that the sound-amplitude based distance measurement can estimate whether an encounter is a close contact (within 3 meters) using a ‘threshold’ of the amplitude. The use of sound amplitude eliminates situations where the usage of only Bluetooth would show false positives. The proposed approach is the first work that integrates Blockchain, Bluetooth and sound amplitude for proximity detection to the best of our knowledge. Overall, the system shows promising results in distance estimation than if only a Bluetooth implementation is used.