Nudging folks towards stronger password choices:providing certainty is the key

Persuading people to choose strong passwords is challenging. One way to influence password strength, as and when people are making the choice, is to tweak the choice architecture to encourage stronger choice. A variety of choice architecture manipulations i.e. “nudges”, have been trialled by researchers with a view to strengthening the overall password profile. None has made much of a difference so far. Here we report on our design of an influential behavioural intervention tailored to the password choice context: a hybrid nudge that significantly prompted stronger passwords.We carried out three longitudinal studies to analyse the efficacy of a range of “nudges” by manipulating the password choice architecture of an actual university web application. The first and second studies tested the efficacy of several simple visual framing “nudges”. Password strength did not budge. The third study tested expiration dates directly linked to password strength. This manipulation delivered a positive result: significantly longer and stronger passwords. Our main conclusion was that the final successful nudge provided participants with absolute certainty as to the benefit of a stronger password, and that it was this certainty that made the difference

Usability of Humanly Computable Passwords

Reusing passwords across multiple websites is a common practice that compromises security. Recently, Blum and Vempala have proposed password strategies to help people calculate, in their heads, passwords for different sites without dependence on third-party tools or external devices. Thus far, the security and efficiency of these "mental algorithms" has been analyzed only theoretically. But are such methods usable? We present the first usability study of humanly computable password strategies, involving a learning phase (to learn a password strategy), then a rehearsal phase (to login to a few websites), and multiple follow-up tests. In our user study, with training, participants were able to calculate a deterministic eight-character password for an arbitrary new website in under 20 seconds

Gathering realistic authentication performance data through field trials

Most evaluations of novel authentication mechanisms have been conducted under laboratory conditions. We argue that the results of short-term usage under laboratory conditions do not predict user performance “in the wild”, because there is insufficient time between enrolment and testing, the number of authentications is low, and authentication is presented as a primary task, rather then the secondary task as it is “in the wild”. User generated reports of performance on the other hand provide subjective data, so reports on frequency of use, time intervals, and success or failure of authentication are subject to the vagaries of users ’ memories. Studies on authentication that provide objective performance data under real-world conditions are rare. In this paper, we present our experiences with a study method that tries to control frequency and timing of authentication, and collects reliable performance data, while maintaining ecological validity of the authentication context at the same time. We describe the development of an authentication server called APET, which allows us to prompt users enrolled in trial cohorts to authenticate at controlled intervals, and report our initial experiences with trials. We conclude by discussing remaining challenges in obtaining reliable performance data through a field trial method such as this one

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

Exploring the Impact of Password Dataset Distribution on Guessing

Leaks from password datasets are a regular occurrence. An organization may defend a leak with reassurances that just a small subset of passwords were taken. In this paper we show that the leak of a relatively small number of text-based passwords from an organizations' stored dataset can lead to a further large collection of users being compromised. Taking a sample of passwords from a given dataset of passwords we exploit the knowledge we gain of the distribution to guess other samples from the same dataset. We show theoretically and empirically that the distribution of passwords in the sample follows the same distribution as the passwords in the whole dataset. We propose a function that measures the ability of one distribution to estimate another. Leveraging this we show that a sample of passwords leaked from a given dataset, will compromise the remaining passwords in that dataset better than a sample leaked from another source