P.C. van Oorschot

The Quest to Replace Passwords: A Framework for Comparative Evaluation of Web Authentication Schemes

We evaluate two decades of proposals to replace text passwords for general-purpose user authentication on the web using a broad set of twenty-five usability, deployability and security benefits that an ideal scheme might provide. The scope of proposals we survey is also extensive, including password management software, federated login protocols, graphical password schemes, cognitive authentication schemes, one-time passwords, hardware tokens, phone-aided schemes and biometrics. Our comprehensive approach leads to key insights about the difficulty of replacing passwords. Not only does no known scheme come close to providing all desired benefits: none even retains the full set of benefits that legacy passwords already provide. In particular, there is a wide range from schemes offering minor security benefits beyond legacy passwords, to those offering significant security benefits in return for being more costly to deploy or more difficult to use. We conclude that many academic proposals have failed to gain traction because researchers rarely consider a sufficiently wide range of real-world constraints. Beyond our analysis of current schemes, our framework provides an evaluation methodology and benchmark for future web authentication proposals.

Graphical passwords: Learning from the first twelve years

Starting around 1999, a great many graphical password schemes have been proposed as alternatives to text-based password authentication. We provide a comprehensive overview of published research in the area, covering both usability and security aspects as well as system evaluation. The article first catalogues existing approaches, highlighting novel features of selected schemes and identifying key usability or security advantages. We then review usability requirements for knowledge-based authentication as they apply to graphical passwords, identify security threats that such systems must address and review known attacks, discuss methodological issues related to empirical evaluation, and identify areas for further research and improved methodology.

On unifying some cryptographic protocol logics

We present a logic for analyzing cryptographic protocols. This logic encompasses a unification of four of its predecessors in the BAN family of logics, namely those given by Li Gong et al. (1990); M. Abadi, M. Tuttle (1991); P.C. van Oorschot (1993); and BAN itself (M. Burrows et al., 1989). We also present a model-theoretic semantics with respect to which the logic is sound. The logic presented captures all of the desirable features of its predecessors and more; nonetheless, it accomplishes this with no more axioms or rules than the simplest of its predecessors.<<ETX>>

Graphical password authentication using cued click points

We propose and examine the usability and security of Cued Click Points (CCP), a cued-recall graphical password technique. Users click on one point per image for a sequence of images. The next image is based on the previous click-point. We present the results of an initial user study which revealed positive results. Performance was very good in terms of speed, accuracy, and number of errors. Users preferred CCP to PassPoints (Wiedenbeck et al., 2005), saying that selecting and remembering only one point per image was easier, and that seeing each image triggered their memory of where the corresponding point was located. We also suggest that CCP provides greater security than PassPoints because the number of images increases the workload for attackers.

Multiple password interference in text passwords and click-based graphical passwords

The underlying issues relating to the usability and security of multiple passwords are largely unexplored. However, we know that people generally have difficulty remembering multiple passwords. This reduces security since users reuse the same password for different systems or reveal other passwords as they try to log in. We report on a laboratory study comparing recall of multiple text passwords with recall of multiple click-based graphical passwords. In a one-hour session (short-term), we found that participants in the graphical password condition coped significantly better than those in the text password condition. In particular, they made fewer errors when recalling their passwords, did not resort to creating passwords directly related to account names, and did not use similar passwords across multiple accounts. After two weeks, participants in the two conditions had recall success rates that were not statistically different from each other, but those with text passwords made more recall errors than participants with graphical passwords. In our study, click-based graphical passwords were significantly less susceptible to multiple password interference in the short-term, while having comparable usability to text passwords in most other respects.

A second look at the usability of click-based graphical passwords

Click-based graphical passwords, which involve clicking a set of user-selected points, have been proposed as a usable alternative to text passwords. We conducted two user studies: an initial lab study to revisit these usability claims, explore for the first time the impact on usability of a wide-range of images, and gather information about the points selected by users; and a large-scale field study to examine how click-based graphical passwords work in practice. No such prior field studies have been reported in the literature. We found significant differences in the usability results of the two studies, providing empirical evidence that relying solely on lab studies for security interfaces can be problematic. We also present a first look at whether interference from having multiple graphical passwords affects usability and whether more memorable passwords are necessarily weaker in terms of security.

Persuasive Cued Click-Points: Design, Implementation, and Evaluation of a Knowledge-Based Authentication Mechanism

This paper presents an integrated evaluation of the Persuasive Cued Click-Points graphical password scheme, including usability and security evaluations, and implementation considerations. An important usability goal for knowledge-based authentication systems is to support users in selecting passwords of higher security, in the sense of being from an expanded effective security space. We use persuasion to influence user choice in click-based graphical passwords, encouraging users to select more random, and hence more difficult to guess, click-points.

SoK: SSL and HTTPS: Revisiting Past Challenges and Evaluating Certificate Trust Model Enhancements

Internet users today depend daily on HTTPS for secure communication with sites they intend to visit. Over the years, many attacks on HTTPS and the certificate trust model it uses have been hypothesized, executed, and/or evolved. Meanwhile the number of browser-trusted (and thus, de facto, user-trusted) certificate authorities has proliferated, while the due diligence in baseline certificate issuance has declined. We survey and categorize prominent security issues with HTTPS and provide a systematic treatment of the history and on-going challenges, intending to provide context for future directions. We also provide a comparative evaluation of current proposals for enhancing the certificate infrastructure used in practice.

On interdomain routing security and pretty secure BGP (psBGP)

It is well known that the Border Gateway Protocol (BGP), the IETF standard interdomain routing protocol, is vulnerable to a variety of attacks, and that a single misconfigured or malicious BGP speaker could result in large-scale service disruption. In this paper, we present Pretty Secure BGP (psBGP)---a proposal for securing BGP, including an architectural overview, design details for significant aspects, and preliminary security and operational analysis. psBGP differs from other security proposals (e.g., S-BGP and soBGP) in that it makes use of a single-level PKI for AS number authentication, a decentralized trust model for verifying the propriety of IP prefix origin, and a rating-based stepwise approach for AS_PATH (integrity) verification. psBGP trades off the strong security guarantees of S-BGP for presumed-simpler operation, e.g., using a PKI with a simple structure, with a small number of certificate types, and of manageable size. psBGP is designed to successfully defend against various (nonmalicious and malicious) threats from uncoordinated BGP speakers, and to be incrementally deployed with incremental benefits.

On predictive models and user-drawn graphical passwords

In commonplace text-based password schemes, users typically choose passwords that are easy to recall, exhibit patterns, and are thus vulnerable to brute-force dictionary attacks. This leads us to ask whether other types of passwords (e.g., graphical) are also vulnerable to dictionary attack because of users tending to choose memorable passwords. We suggest a method to predict and model a number of such classes for systems where passwords are created solely from a users memory. We hypothesize that these classes define weak password subspaces suitable for an attack dictionary. For user-drawn graphical passwords, we apply this method with cognitive studies on visual recall. These cognitive studies motivate us to define a set of password complexity factors (e.g., reflective symmetry and stroke count), which define a set of classes. To better understand the size of these classes and, thus, how weak the password subspaces they define might be, we use the “Draw-A-Secret” (DAS) graphical password scheme of Jermyn et al. [1999] as an example. We analyze the size of these classes for DAS under convenient parameter choices and show that they can be combined to define apparently popular subspaces that have bit sizes ranging from 31 to 41—a surprisingly small proportion of the full password space (58 bits). Our results quantitatively support suggestions that user-drawn graphical password systems employ measures, such as graphical password rules or guidelines and proactive password checking.