# SPIN: A Blockchain-Based Framework for Sharing COVID-19 Pandemic Information across Nations
## 1 Introduction  
The COVID-19 pandemic has caused many countries around the globe to adopt strict policies and measures in an attempt to control the rapid spread of the virus. These policies include enforcing social distancing, schools and universities closure, and travel restrictions [1, 2, 3, 4]. Reports show that the pandemic has caused nearly 90% of commercial flights to be grounded, and has made more than 130 countries introduce some forms of travel restrictions, including quarantine, screening, or travel banning to high-risk countries [5]. The United Nations Conference on Trade and Development (UNCTAD) estimates the loss in the international tourism sector to be at least $1.2 trillion [6]. As living with the virus is becoming the norm, countries have started lifting some travel restrictions. For example, many countries require negative polymerase chain reaction (PCR) test results, vaccination certificates, or certificates of having recovered from COVID-19 [7]. Enforcing these travel requirements raises several challenges, such as the ability to verify the authenticity of vaccination and test records. Extensive research has been conducted to tackle the challenges associated with the COVID-19 pandemic. Researchers proposed multiple techniques for sharing health-related records [8, 9, 10, 11, 12, 13, 14, 15]. Most of the proposed techniques utilize blockchain technology to provide mechanisms for sharing health-related information without relying on a central authority [8, 9, 10, 11]. The majority of existing approaches rely on cryptography techniques to publish encrypted personal healthrecords in the public blockchain; to preserve privacy, much of these data do not need to be in the blockchain. Unlike previously proposed techniques, our approach provides a secure and privacy-preserving mechanism for sharing both public data and private data of individuals. COVID-19 data feeds with personal data being anonymized, such as records of new COVID-19 tests, cases, and vaccinations provided, may be shared publicly with other countries [16; 17; 18]. Such data feeds would help in estimating the contemporary risk level associated with each participating country. In addition, personal private data, such as test and vaccine certificates of individuals traveling to specific countries, may only be shared with the travel destination countries to preserve privacy, i.e., without being pushed to the blockchain. This motivates our work in developing a framework for sharing both public and private health-related information between countries. In this paper, we introduce SPIN [19] (a framework for Sharing Pandemic Information across Nations). SPIN is a blockchain-based framework that allows countries to quickly verify COVID-19 vaccination and test results at their ports of entry. Countries are represented as peers in the blockchain network. A country may select a local authority to act as a peer in the decentralized network (e.g., a ministry of health). In the blockchain network, local entities that administer public health facilities and control ports of entry are represented as clients connecting to their country's peer. Moreover, clients may invoke transactions to read/write public and private data, and peers may share public data by executing transactions to the blockchain network. Public data are transformed and stored in the form of key-value pairs, allowing other peers in the network to read it. Additionally, each peer may send private data to a recipient peer. For sharing private data, such as COVID-19 test results, we utilize cancelable fingerprint templates to authenticate information about individuals. More specifically, the contribution of our paper is as follows:  
1. A decentralized framework (SPIN) for sharing COVID-19 vaccination and test certificates as well as public health-related data. 2. A publicly available implementation of our framework. 3. A detailed analysis of the properties associated with the design decisions we chose for the framework in terms of efficiency, scalability, security, and privacy. 4.