Evaluating Dynamic Tor Onion Services for Privacy Preserving Distributed Digital Identity Systems

Digital identity documents provide several key benefits over physical ones. They can be created more easily, incur less costs, improve usability and can be updated if necessary. However, the deployment of digital identity systems does come with several challenges regarding both security and privacy of personal information. In this paper, we highlight one challenge that digital identity systems face if they are set up in a distributed fashion: Network Unlinkability. We discuss why network unlinkability is so critical for a distributed digital identity system that wants to protect the privacy of its users and present a specific definition of unlinkability for our use-case. Based on this definition, we propose a scheme that utilizes the Tor network to achieve the required level of unlinkability by dynamically creating onion services and evaluate the feasibility of our approach by measuring the deployment times of onion services.