A comprehensive study of the usability of multiple graphical passwords

Recognition-based graphical authentication systems (RBGSs) using images as passwords have been proposed as one potential solution to the need for more usable authentication. The rapid increase in the technologies requiring user authentication has increased the number of passwords that users have to remember. But nearly all prior work with RBGSs has studied the usability of a single password. In this paper, we present the first published comparison of the usability of multiple graphical passwords with four different image types: Mikon, doodle, art and everyday objects (food, buildings, sports etc.). A longi-tudinal experiment was performed with 100 participants over a period of 8 weeks, to examine the usability performance of each of the image types. The re-sults of the study demonstrate that object images are most usable in the sense of being more memorable and less time-consuming to employ, Mikon images are close behind but doodle and art images are significantly inferior. The results of our study complement cognitive literature on the picture superiority effect, vis-ual search process and nameability of visually complex images

Multicriteria optimization to select images as passwords in recognition based graphical authentication systems

Usability and guessability are two conflicting criteria in assessing the suitability of an image to be used as password in the recognition based graph -ical authentication systems (RGBSs). We present the first work in this area that uses a new approach, which effectively integrates a series of techniques in order to rank images taking into account the values obtained for each of the dimen -sions of usability and guessability, from two user studies. Our approach uses fuzzy numbers to deal with non commensurable criteria and compares two multicriteria optimization methods namely, TOPSIS and VIKOR. The results suggest that VIKOR method is the most applicable to make an objective state-ment about which image type is better suited to be used as password. The paper also discusses some improvements that could be done to improve the ranking assessment

The Slowdown in Soviet Defense Expenditures: Comment

The reason for the apparently opposing results in Brada and Graves\u27 (1988) attempt to explain the reasons for the slowdown in USSR defense expenditures in the mid-1970s is that their analysis suffers from a serious serial correlation problem. The majority of the regressions display Durbin-Watson statistics that reject the null hypothesis of no autocorrelation. A reestimation of their results, after correcting for serial correlation, changes some of their major conclusions regarding the factors influencing Soviet defense spending. The corrected results indicate that no structural break occurred in the mid-1970s. These results suggest that there has been no change in Soviet military doctrine or in the Soviet leadership\u27s preferences in the 1970s. In reply, Brada and Graves argue that the evidence for the existence of serially correlated disturbances is much more tenuous than Chowdhury suggests and that the evidence is more consistent with the existence of a structural break and no serial correlation of disturbances

The Slowdown in Soviet Defense Expenditures: Comment

The reason for the apparently opposing results in Brada and Graves\u27 (1988) attempt to explain the reasons for the slowdown in USSR defense expenditures in the mid-1970s is that their analysis suffers from a serious serial correlation problem. The majority of the regressions display Durbin-Watson statistics that reject the null hypothesis of no autocorrelation. A reestimation of their results, after correcting for serial correlation, changes some of their major conclusions regarding the factors influencing Soviet defense spending. The corrected results indicate that no structural break occurred in the mid-1970s. These results suggest that there has been no change in Soviet military doctrine or in the Soviet leadership\u27s preferences in the 1970s. In reply, Brada and Graves argue that the evidence for the existence of serially correlated disturbances is much more tenuous than Chowdhury suggests and that the evidence is more consistent with the existence of a structural break and no serial correlation of disturbances