Soulbound Token for Covid-19 Vaccination Certification.

Soulbound Tokens were introduced last May by Vitalik Buterin as a new kind of non-fungible, non-transferable token in the Ethereum ecosystem. The main idea behind such tokens is that they are born and die at the same address without ever changing ownership. Because there is typically no one-to-one correspondence between blockchain addresses and people, asserting that such new tokens are associated with a person for life is a strong assertion. Nevertheless, these new tokens promise to envision practical applications related to personal reputation or ownership of specific, non-transferable assets, and their real-world potential applications remain largely unexplored. In this paper, we present a practical application of such tokens, investigating a use case where a real-world problem largely impacting modern life has been exploited: COVID vaccine certification. The approach can easily be extended to other vaccination cases and relies on the use of a DApp where Soulbound Tokens have been implemented. In our scheme, two main actors are involved. The system administrator, represented by a local medical organization, is able to insert into a database the list of vaccines for which certification will be sent, and the citizen, after receiving the vaccination, will be able to receive and visualize the certifications provided by the first actor.