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1. Don't Forget the Stuffing! Revisiting the Security Impact of Typo-Tolerant Password Authentication

   https://doi.org/10.1145/3460120.3484791  

   Sahin, Sena ; Li, Frank ( November 2021 , ACM SIGSAC Conference on Computer and Communications Security)

   To enhance the usability of password authentication, typo-tolerant password authentication schemes permit certain deviations in the user-supplied password, to account for common typographical errors yet still allow the user to successfully log in. In prior work, analysis by Chatterjee et al. demonstrated that typo-tolerance indeed notably improves password usability, yet (surprisingly) does not appear to significantly degrade authentication security. In practice, major web services such as Facebook have employed typo-tolerant password authentication systems. In this paper, we revisit the security impact of typo-tolerant password authentication. We observe that the existing security analysis of such systems considers only password spraying attacks. However, this threat model is incomplete, as password authentication systems must also contend with credential stuffing and tweaking attacks. Factoring in these missing attack vectors, we empirically re-evaluate the security impact of password typo-tolerance using password leak datasets, discovering a significantly larger degradation in security. To mitigate this issue, we explore machine learning classifiers that predict when a password's security is likely affected by typo-tolerance. Our resulting models offer various suitable operating points on the functionality-security tradeoff spectrum, ultimately allowing for partial deployment of typo-tolerant password authentication, preserving its functionality for many users while reducing the security risks. 

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2. Understanding Attacking Behaviors Toward Password-based Mobile User Authentication

   Lina Zhou, Kanlun Wang ( July 2021 , Who Are You?! Adventures in Authentication Workshop)

   Password-based mobile user authentication is vulnerable to a variety of security threats. Shoulder-surfing is the key to those security threats. Despite a large body of research on password security with mobile devices, existing studies have focused on shaping the security behavior of mobile users by enhancing the strengths of user passwords or by establishing secure password composition policies. There is little understanding of how an attacker actually goes about observing the password of a target user. This study empirically examines attackers’ behaviors in observing passwordbased mobile user authentication sessions across the three observation attempts. It collects data through a longitudinal user study and analyzes the data collected through a system log. The results reveal several behavioral patterns of attackers. The findings suggest that attackers are strategic in deploying attacks of shoulder-surfing. The findings have implications for enhancing users’ password security and refining organizations’ password composition policies. 

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3. DALock: Password Distribution-Aware Throttling

   Blocki, Jeremiah ; Zhang, Wuwei. ( January 2022 , Proceedings on Privacy Enhancing Technologies)

   Large-scale online password guessing attacks are widespread and pose a persistant privacy and security threat to users. The common method for mitigating the risk of online cracking is to lock out the user after a fixed number ($K$) of consecutive incorrect login attempts. Selecting the value of $K$ induces a classic security-usability trade-off. When $K$ is too large, a hacker can (quickly) break into a significant fraction of user accounts, but when $K$ is too low, we will start to annoy honest users by locking them out after a few mistakes. Motivated by the observation that honest user mistakes typically look quite different from an online attacker's password guesses, we introduce $\DALock$, a {\em distribution-aware} password lockout mechanism to reduce user annoyance while minimizing user risk. As the name suggests, $\DALock$ is designed to be aware of the frequency and popularity of the password used for login attacks. At the same time, standard throttling mechanisms (e.g., $K$-strikes) are oblivious to the password distribution. In particular, $\DALock$ maintains an extra ``hit count" in addition to ``strike count" for each user, which is based on (estimates of) the cumulative probability of {\em all} login attempts for that particular account. We empirically evaluate $\DALock$ with an extensive battery of simulations using real-world password datasets. In comparison with the traditional $K$-strikes mechanism, {our simulations indicate that} $\DALock$ offers a superior {simulated} security/usability trade-off. For example, in one of our simulations, we are able to reduce the success rate of an attacker to $0.05\%$ (compared to $1\%$ for the $3$-strikes mechanism) whilst simultaneously reducing the unwanted lockout rate for accounts that are not under attack to just $0.08\%$ (compared to $4\%$ for the $3$-strikes mechanism). 

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4. Two-factor Password-authenticated Key Exchange with End-to-end Security

   https://doi.org/10.1145/3446807  

   Jarecki, Stanislaw ; Jubur, Mohammed ; Krawczyk, Hugo ; Saxena, Nitesh ; Shirvanian, Maliheh ( August 2021 , ACM Transactions on Privacy and Security)

   null (Ed.)

   We present a secure two-factor authentication (TFA) scheme based on the user’s possession of a password and a crypto-capable device. Security is “end-to-end” in the sense that the attacker can attack all parts of the system, including all communication links and any subset of parties (servers, devices, client terminals), can learn users’ passwords, and perform active and passive attacks, online and offline. In all cases the scheme provides the highest attainable security bounds given the set of compromised components. Our solution builds a TFA scheme using any Device-enhanced Password-authenticated Key Exchange (PAKE), defined by Jarecki et al., and any Short Authenticated String (SAS) Message Authentication, defined by Vaudenay. We show an efficient instantiation of this modular construction, which utilizes any password-based client-server authentication method, with or without reliance on public-key infrastructure. The security of the proposed scheme is proven in a formal model that we formulate as an extension of the traditional PAKE model. We also report on a prototype implementation of our schemes, including TLS-based and PKI-free variants, as well as several instantiations of the SAS mechanism, all demonstrating the practicality of our approach. Finally, we present a usability study evaluating the viability of our protocol contrasted with the traditional PIN-based TFA approach in terms of efficiency, potential for errors, user experience, and security perception of the underlying manual process. 1 

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5. Behaviors of Unwarranted Password Identification via Shoulder-Surfing during Mobile Authentication

   https://doi.org/10.1109/ISI53945.2021.9624730  

   Zhou, Lina ; Wang, Kanlun ; Lai, Jianwei ; Zhang, Dongsong ( November 2021 , IEEE International Conference on Intelligence and Security Informatics (ISI))

   Password-based mobile user authentication is vulnerable to shoulder-surfing. Despite the increasing research on user password entry behavior and mobile security, there is limited understanding of how an adversary identifies a password through shoulder-surfing during mobile authentication. This study empirically examines the behaviors and strategies of password identification through shoulder-surfing with multiple observation attempts and from different observation distances. The results of analyzing data collected from a user study reveal the strategies and dynamics of password identification behaviors. The findings have implications for enhancing users’ password security and improving the design of mobile authentication methods. 

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