Biblio

This paper presents a possible implementation of progressive authentication using the Android pattern lock. Our key idea is to use one pattern for two access levels to the device; an abridged pattern is used to access generic applications and a second, extended and higher-complexity pattern is used less frequently to access more sensitive applications. We conducted a user study of 89 participants and a consecutive user survey on those participants to investigate the usability of such a pattern scheme. Data from our prototype showed that for unlocking lowsecurity applications the median unlock times for users of the multiple pattern scheme and conventional pattern scheme were 2824 ms and 5589 ms respectively, and the distributions in the two groups differed significantly (Mann-Whitney U test, p-value less than 0.05, two-tailed). From our user survey, we did not find statistically significant differences between the two groups for their qualitative responses regarding usability and security (t-test, p-value greater than 0.05, two-tailed), but the groups did not differ by more than one satisfaction rating at 90% confidence.

We conducted a series of in-depth focus groups wherein users provided rationales for their own online privacy behaviors. Our data suggest that individuals often take action with little thought or evaluation, even showing surprise when confronted with their own behaviors. Our analysis yielded a battery of cognitive heuristics, i.e., mental shortcuts / rules of thumb, that users seem to employ when they disclose or withhold information at the spur of the moment. A total of 4 positive heuristics (promoting disclosure) and 4 negative heuristics (inhibiting disclosure) were discovered. An understanding of these heuristics can be valuable for designing interfaces that promote secure and trustworthy computing.