Wouter Lueks Seda F. Gürses Michael Veale Edouard Bugnion Marcel Salathé Kenneth G. Paterson Carmela Troncoso CrowdNotifier: Decentralized Privacy-Preserving Presence Tracing. 350-368 2021 2021 Proc. Priv. Enhancing Technol. 4 https://doi.org/10.2478/popets-2021-0074 db/journals/popets/popets2021.html#LueksGVBSPT21