# Privacy-Preserving Solution for European Union Digital Vaccine Certificates
###### Abstract  
The recent COVID-19 pandemic situation highlights the importance of digital vaccine certificates. In response, the European Union (EU) developed EU Digital Vaccine Certificates to enable proof of non-infectivity and completed vaccinations. However, these solutions suffer from several shortcomings, such as ineffective certificate holder identification and a high violation of user privacy with the disclosure of sensitive information. In this work, we present a novel solution for privacy-preserving EU Digital Vaccine Certificates. Our solution solves the aforementioned privacy and security shortcomings and is in line with current EU legislation, i.e., the General Data Protection Regulation (GDPR), the upcoming revision of the electronic IDentification, Authentication, and trust Services (eIDAS), called regulation eIDAS 2.0, and the new tools that it envisages to be led by European digital identity. This identity is intended to allow citizens to prove their identity to access online services, share digital documents, or simply prove specific personal characteristics such as age without revealing their identity or other personal information. The core of our proposal is built on our novel attribute-based credential scheme, which can be easily implemented on various handheld devices, especially on Android smartphones and smartwatches. However, due to the lightweight nature of our scheme, it can also be implemented on constrained devices such as smart cards. In order to demonstrate the security, privacy, and practicality inherent in our proposal, we provide the security analysis of the cryptographic core along with a set of experimental results conducted on smartphones and smart cards. digital vaccine certificate; COVID-19; attribute-based credential; authentication; cryptography; security; privacy; Android; Bluetooth Low Energy; smart cards Article Privacy-Preserving Solution for Vaccine Certificates  
schemes, these schemes verify only the possession of specific attributes, e.g., age, driving license, authorization to access a protected area, type of traffic ticket, or possession of a COVID-19 certificate. Attribute-based schemes do not require the verification of specific user identities, such as IDs, user public keys, and shared passwords, that could cause unwanted linking and tracking of individuals. Despite the fact that global pandemic situation is slowly weakening in the world, secure and privacy-preserving COVID-19 or non-infection certificate solutions will be required further. COVID-19 certificate applications can be divided into two basic groups: (1) currently deployed/used solutions, and (2) experimental/academic solutions still under development. The first group includes applications that are used to prove non-infectiousness. These solutions are mainly focused on the usability of the application rather than on data privacy protection, e.g., European Union (EU) Digital COVID Certificates (DCC) ([[https://commission.europa.eu/strategy-and-policy/coronavirus-response/safe-covid-19-vaccines-europeans/eu-digital-covid-certificate_en](https://commission.europa.eu/strategy-and-policy/coronavirus-response/safe-covid-19-vaccines-europeans/eu-digital-covid-certificate_en)]([https://commission.europa.eu/strategy-and-policy/coronavirus-response/safe-covid-19-vaccines-europeans/eu-digital-covid-certificate_en](https://commission.europa.eu/strategy-and-policy/coronavirus-response/safe-covid-19-vaccines-europeans/eu-digital-covid-certificate_en)), accessed on 5 March 2023). Further, some commercial applications are providing a certain level of privacy protection and are often integrated into larger health data management systems. An example is the IBM Digital Health Pass [1], which integrates test results and other health data into one system. Finally, the ongoing development of experimental solutions try to overcome the main issues of the previous applications, primarily focusing on protecting personal data. Well-known and experimental solutions from both groups are extensively explored in Section 2.