Joshua Reynolds Nikita Samarin Joseph D. Barnes Taylor Judd Joshua Mason Michael D. Bailey Serge Egelman Empirical Measurement of Systemic 2FA Usability. 127-143 2020 USENIX Security Symposium https://www.usenix.org/conference/usenixsecurity20/presentation/reynolds conf/uss/2020 db/conf/uss/uss2020.html#ReynoldsSBJMBE20