The most commonly adopted password management technique is to store web account passwords on a password manager and lock them using a master password. However, current online password managers do not hide the account passwords or the master password from the password manager itself, which highlights their real-world vulnerability and lack of user confidence in the face of malicious insiders and outsiders that compromise the password management service especially given its online nature. We attempt to address this crucial vulnerability in the design of online password managers by proposing a cloud-based password manager that does not learn or store master passwords and account passwords. We introduce the protocol design and report on a full implementation of the system. Our implementation provides several security features, including enforcement of a unique and secure password per each service, robustness to online password guessing attacks against the password manager and the web service, robustness to password dictionary attacks upon compromise of the password manager and the web service, and security against phishing attacks. Furthermore, to assess users’ perceptions of the security and usability of our password manager, we conducted a lab-based study. The findings from the study suggest that our system is close to being practical for everyday use and is viewed by users as both usable and more secure/trustworthy.

Push-based two-factor authentication (2FA) methods, such as the ”Just-Confirm” approach, are popular due to their user-friendly design, requiring users to simply approve or deny a push notification on their mobile device. However, these methods are vulnerable to ”concurrency attacks,” where an attacker attempts to log in immediately after the legitimate user, causing multiple push notifications that may lead to users inadvertently approving fraudulent access. This vulnerability arises because the login notifications are not uniquely bound to individual login attempts. To address this issue, Push-Compare-and-Confirm 2FA method enhances security by associating each login notification with a unique code displayed on both the authentication terminal and the push notification. Users are required to match these codes before confirming access, thereby binding the notification to a specific login attempt. Recognizing the ubiquity of mobile devices in daily life, we conducted a comprehensive user study with 65 participants to evaluate the usability and security of Push-Compare-and-Confirm. The study considered two scenarios: one where the user’s second-factor device (phone) is physically separate from the authentication terminal (e.g., logging in on a PC and confirming on the phone), and another where the phone serves as both the authentication terminal and the second-factor device. Participants completed 24 login trials, including both benign and attack scenarios, with varying code lengths (four characters and six characters). Our results indicate that while Push-Compare-and-Confirm maintains high usability in benign scenarios, with True Positive Rates (TPR) exceeding 95%, it presents significant challenges in attack detection. Participants correctly identified only about 50% of fraudulent login attempts, indicating a substantial vulnerability remains. These findings suggest that although Push-Compare-and-Confirm enhances security over standard push-based 2FA methods, additional measures—such as more intuitive interface designs, clearer visual cues, and user education on the importance of code verification—are necessary to improve attack detection rates without compromising usability.

Two-factor authentication (2FA) systems aim to secure user accounts, provided that either the password or the second factor device remains uncompromised. However, in this research, we challenge this perception and analyze the security of FIDO2 hardware security keys, which are increasingly used in 2FA and passwordless systems. Specifically, we develop an attack framework, analyze the underlying protocols of FIDO2, and examine the associated OS-level security. Through practical demonstrations, we illustrate how adversaries can exploit this framework and OS-level security measures to execute our designed attack, known as FIDOLA (FIDO2 Deception Attack via Overlays exploiting Limited Display Authenticators).

Notification-based authentication is an emerging Two-Factor Authentication (2FA) and passwordless solution that leverages interactive notifications on mobile devices to establish an additional layer of security beyond passwords. This method has gained popularity due to its convenience and ease of deployment in organizational settings. In this work, we aim to evaluate the effectiveness of notification-based authentication systems when a malicious entity is present on the user's computer, such as a keylogger or malicious extension, without compromising the mobile devices or communication channels. Furthermore, we investigate how the lack of information provided to users during the authentication workflow can lead to the approval of malicious authentication requests. Notably, we highlight the vulnerability of cross-service attacks, where an attacker authenticates to Service B while the user is attempting to authenticate to Service A. Our proof-of-concept attack program demonstrates the susceptibility of various notification-based authentication systems, and our user study reveals an alarming 82.2% cross-service attack success rate. These findings suggest a potential vulnerability in notification-based authentication systems, where the attacker compromise user account without compromising possession-factor device, such as smartphones.

Second factor (2FA) or passwordless authentication based on notifications pushed to a user's personal device (e.g., a phone) that the user can simply approve (or deny) has become widely popular due to its convenience. In this paper, we show that the effortlessness of this approach gives rise to a fundamental design vulnerability. The vulnerability stems from the fact that the notification, as shown to the user, is not uniquely bound to the user's login session running through the browser, and thus if two notifications are sent around the same time (one for the user's session and one for an attacker's session), the user may not be able to distinguish between the two, likely ending up accepting the notification of the attacker's session.

In this paper, we highlight a fundamental vulnerability associated with the widely adopted “Just Tap” push-based authentication in the face of a concurrency attack, and propose the method REPLICATE, a redesign to counter this vulnerability. In the concurrency attack, the attacker launches the login session at the same time the user initiates a session, and the user may be fooled, with high likelihood, into accepting the push notification which corresponds to the attacker's session, thinking it is their own. The attack stems from the fact that the login notification is not explicitly mapped to the login session running on the browser in the Just Tap approach. REPLICATE attempts to address this fundamental flaw by having the user approve the login attempt by replicating the information presented on the browser session over to the login notification, such as by moving a key in a particular direction, choosing a particular shape, etc. We report on the design and a systematic usability study of REPLICATE. Even without being aware of the vulnerability, in general, participants placed multiple variants of REPLICATE in competition to the Just Tap and fairly above PIN-based authentication.

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