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

Naturally Rehearsing Passwords

We introduce quantitative usability and security models to guide the design of password management schemes --- systematic strategies to help users create and remember multiple passwords. In the same way that security proofs in cryptography are based on complexity-theoretic assumptions (e.g., hardness of factoring and discrete logarithm), we quantify usability by introducing usability assumptions. In particular, password management relies on assumptions about human memory, e.g., that a user who follows a particular rehearsal schedule will successfully maintain the corresponding memory. These assumptions are informed by research in cognitive science and validated through empirical studies. Given rehearsal requirements and a user's visitation schedule for each account, we use the total number of extra rehearsals that the user would have to do to remember all of his passwords as a measure of the usability of the password scheme. Our usability model leads us to a key observation: password reuse benefits users not only by reducing the number of passwords that the user has to memorize, but more importantly by increasing the natural rehearsal rate for each password. We also present a security model which accounts for the complexity of password management with multiple accounts and associated threats, including online, offline, and plaintext password leak attacks. Observing that current password management schemes are either insecure or unusable, we present Shared Cues--- a new scheme in which the underlying secret is strategically shared across accounts to ensure that most rehearsal requirements are satisfied naturally while simultaneously providing strong security. The construction uses the Chinese Remainder Theorem to achieve these competing goals

Lessons learned from evaluating eight password nudges in the wild

Background. The tension between security and convenience, when creating passwords, is well established. It is a tension that often leads users to create poor passwords. For security designers, three mitigation strategies exist: issuing passwords, mandating minimum strength levels or encouraging better passwords. The first strategy prompts recording, the second reuse, but the third merits further investigation. It seemed promising to explore whether users could be subtly nudged towards stronger passwords.Aim. The aim of the study was to investigate the influence of visual nudges on self-chosen password length and/or strength.Method. A university application, enabling students to check course dates and review grades, was used to support two consecutive empirical studies over the course of two academic years. In total, 497 and 776 participants, respectively, were randomly assigned either to a control or an experimental group. Whereas the control group received no intervention, the experimental groups were presented with different visual nudges on the registration page of the web application whenever passwords were created. The experimental groups’ password strengths and lengths were then compared that of the control group.Results. No impact of the visual nudges could be detected, neither in terms of password strength nor length. The ordinal score metric used to calculate password strength led to a decrease in variance and test power, so that the inability to detect an effect size does not definitively indicate that such an effect does not exist.Conclusion. We cannot conclude that the nudges had no effect on password strength. It might well be that an actual effect was not detected due to the experimental design choices. Another possible explanation for our result is that password choice is influenced by the user’s task, cognitive budget, goals and pre-existing routines. A simple visual nudge might not have the power to overcome these forces. Our lessons learned therefore recommend the use of a richer password strength quantification measure, and the acknowledgement of the user’s context, in future studies

Integrating a web-based system with business processes in closed loop supply chains

Closed Loop Supply Chains include operations for physical collection of end-of-use products, selection based on their configuration and/or condition and decision making for reuse, remanufacturing or recycling. Uncertainty factors regarding the time, place of origin, and status of returns introduce many difficulties in planning these operations. With the aim to minimize such problems, this paper presents an architecture for virtual reverse logistics networks and an implementation for end-of-use PCs. The virtual reverse logistics network for PCs relies on E-commerce and WWW technologies for remote monitoring and benchmarking, instead of physical transportation and inspection. A configuration monitoring and benchmarking agent screens the computer that is about to enter the end-of-use stream and registers the data in the system’s databases. The virtual reverse logistics network regards all incoming PCs as submitted offers. Also, users or agents may explicitly register requests for PCs or modules. Offers are matched to requests with a decision support system to provide recommendations for reuse, remanufacturing or recycling of end-of-use PCs. An electronic marketplace matches requests and offers. The proposed architecture diminishes the uncertainty factors and provides us with an understanding on what is missing and it is likely to have a positive impact to the development of virtual reverse logistics networks for computers and other equipment with embedded logic.business processes;Closed Loop Supply Chains;virtual reverse logistics networks;web-based system