ThPlA: Threshold Passwordless Authentication Made Usable and Scalable

Passwordless user authentication schemes with FIDO as the standard have been widely deployed in web applications. Users use hardware tokens to store their identity credentials (i.e., signing keys) and implement strong authentication through a challenge-response mechanism, avoiding the security risks associated with traditional password-based authentication. Distributed Web services can greatly alleviate the system reliability problem caused by single points of failure, and thus have received increasing attention and research. In distributed systems, resources are distributed across multiple servers, and users must interact with them (or a subset of them in thresholding) to obtain network services. User authentication among the distributed (threshold) systems also poses a challenge: how to ensure security and ease of use at the same time? In particular, users need to authenticate to multiple servers when accessing distributed services, and in the case of using FIDO authentication, users need to authenticate to each server using challenge-response authentication, which will greatly reduce the user experience. In this work, we propose the concept named Threshold Passwordless Authentication (ThPlA) to address this issue. ThPlA allows users to authenticate to a t-of-n thresholding system. ThPlA is designed to be compatible with existing FIDO tokens and requires no extra hardware modifications; the user only needs to interact with the hardware token once during an authentication session; and on the service side, the servers do not need to communicate with each other. ThPlA is based on the component named Non-interactive Threshold Nonce Generation (NI-ThNG), which extends the two-party challenge-response mechanism to t-of-n settings. We provide a formal definition of ThPlA and NI-ThNG and give practical constructions. We also provide a performance evaluation of ThPlA and NI-ThNG, respectively. Our experimental results show that the schemes are efficient and practical for real-world applications, even in large-scale distributed systems.