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I know what you did last week! Do you? Dynamic security questions for fallback authentication on smartphones

: Hang, A.; Luca, A. de; Hussmann, H.


Kim, J. ; Association for Computing Machinery -ACM-:
CHI 2015 crossings. Proceedings of the 33rd Annual CHI Conference on Human Factors in Computing Systems, CHI 2015 : April 18 - 23, 2015, Seoul, Republic of Korea
New York: ACM, 2015
ISBN: 978-1-4503-3145-6
Conference on Human Factors in Computing Systems (CHI) <33, 2015, Seoul>
Conference Paper
Fraunhofer FKIE ()

In this paper, we present the design and evaluation of dynamic security questions for fallback authentication. In case users lose access to their device, the system asks questions about their usage behavior (e.g. calls, text messages or app usage). We performed two consecutive user studies with real users and real adversaries to identify questions that work well in the sense that they are easy to answer for the genuine user, but hard to guess for an adversary. The results show that app installations and communication are the most promising categories of questions. Using three questions from the evaluated categories was sufficient to get an accuracy of 95.5% - 100%.