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Table 3 Time window-event matrix of a user’s phone call log history

From: Evaluating smartphone-based dynamic security questions for fallback authentication: a field study

Window\day Nov 14 Nov 15 \(\ldots\) Dec 27
\(00:00-00:59\) \(\ldots\) \(\{Received call from-Jeff, 55 s\}\)
\(01:00-01:59\) \(\ldots\)
\(\vdots\) \(\vdots\) \(\vdots\) \(\vdots ~ \vdots ~ \vdots\) \(\vdots\)
\(14:00-14:59\) \(\{Called-Alice, 55\, s\} , \{Called-Bob, 32\, s\}\) \(\{Called-Bob, 89 \,s\}\) \(\ldots\) \(\{Called-Bob, 17\, s\}\)
\(15:00-15:59\) \(\{Called-John, 300\, s\}\) \(\{Received call from-Jeff, 42\, s\}\) \(\ldots\)
\(16:00-16:59\) \(\{Called-John, 14 \,s\}\) \(\{Called-Bob, 20 \,s\}\) \(\ldots\) \(\{Called-Bob, 89 \,s\}\)
\(17:00-17:59\) \(\{Called-Bob, 27\, s\}\) \(\ldots\)
\(\vdots\) \(\vdots\) \(\vdots\) \(\vdots ~ \vdots ~ \vdots\) \(\vdots\)
\(23:00-23:59\) \(\{Received call-Bob, 14 \,s\}\) \(\ldots\) \(\{Called-Mike, 14 \,s\}\)
  1. Numbers right next to a person’s name indicates the duration of the phone calls in seconds