Can blockchain take smartphones out of contact tracing?

The global public health crisis caused by the emergence and spread of the coronavirus disease (COVID-19) has been devastating, prompting the need for immediate countermeasures to curb its spread, especially in the absence of any approved treatment shortly after its onset. This crisis has highlighted the gap in current contact tracing systems, which require massive public participation to be effective but lack a high degree of public acceptance. This low acceptance is mainly due to concerns regarding personal data privacy and guaranteed data protection, hindering the success of existing systems. We evaluate the use of blockchain to improve contact tracing and provide a solution to effectively track the spread of an epidemic, using COVID-19 as a relevant use case. The key requirements of the proposed system include protecting user data, maintaining full transparency using a decentralised system, and eliminating the need of GPS or personal data for contact tracing. A proof-of-concept system uses a private blockchain to secure and manage data collected at various locations using a mobile application or stored-value contactless smart cards. Contact tracing is performed via smart contracts over the blockchain using the collected data. We confirm the improvements provided by the proposed system for contact tracing.