Abstract: Today, most Internet applications still establish user authentication with traditional text based passwords. Designing a secure as well as a user-friendly password-based method has been on the agenda of security researchers for a long time. On one hand, there are password manager programs which facilitate generating site-specific strong passwords from a single user password to eliminate the memory burden due to multiple passwords. On the other hand, there are studies exploring the viability of graphical passwords as a more secure and user-friendly alternative. In this paper, we present GPEX, a password manager program implemented as a web browser plug-in to enable using graphical passwords to secure Internet applications without any need to change their authentication interface. Experimental results show that GPEX has security and usability advantages over other password manager plug-ins. specifically; we find that with the visual interface of GPEX, users have a more complete and accurate mental model of the system and incorrect login attempts causing security exposures can easily be avoided.

Abstract. Identity fraud (IDF) may be defined as unauthorized exploitation of credential information through the use of false identity. We propose CROO, a universal (i.e. generic) infrastructure and protocol to either prevent IDF (by detecting attempts thereof), or limit its consequences (by identifying cases of previously undetected IDF). CROO is a capture resilient one-time password scheme, whereby each user must carry a personal trusted device used to generate one-time passwords (OTPs) verified by online trusted parties. Multiple trusted parties may be used for increased scalability. OTPs can be used regardless of a transaction’s purpose (e.g. user authentication or financial payment), associated credentials, and online or on-site nature; this makes CROO a universal scheme. OTPs are not sent in cleartext; they are used as keys to compute MACs of hashed transaction information, in a manner allowing OTP-verifying parties to confirm that given user credentials (i.e. OTPkeyed MACs) correspond to claimed hashed transaction details. Hashing transaction details increases user privacy. Each OTP is generated from a PIN-encrypted non-verifiable key; this makes users ’ devices resilient to off-line PIN-guessing attacks. CROO’s credentials can be formatted as existing user credentials (e.g. credit cards or driver’s licenses). 1

Abstract. We propose active cookies as a tool for stronger user/client authentication on the Web. An ordinary cookie is automatically released to any server associated with a particular domain name. It is therefore vulnerable to capture by pharming, that is, spoofing of domain names. An active cookie, by contrast, resists such pharming attacks. Active cookies rely on a new protocol we propose that channels client communications to a specific, valid IP address. This protocol exploits a combination of cookie-based (or cached-object-based) authentication with a new type of IP-tracing protocol. This IP-tracing protocol helps defend against the presence of an attacker in the loop during an authentication session, but is unaffected by IP-address changes in clients between sessions. Active cookies are fully transparent to users. They require no explicit installation or behavioral changes from users, and thus avoid the security risks and deployment complications of plug-ins, new login procedures, and standalone applications. While active cookies have functional and security limitations, we believe that they are an attractive countermeasure to a range of phishing and pharming attacks and a useful complement to existing techniques for user authentication. We demonstrate the practicality of active cookies through experimental implementation.

Abstract. The conventional wisdom has always been that users should refrain from entering their sensitive data (such as usernames, passwords, and credit card numbers) into

The security of most password authentication mechanisms hinges on the secrecy of only a single word – if an adversary obtains knowledge of a victim’s password, the adversary will be able to impersonate the victim and gain access to the resources to which the victim is entitled. Although cryptographic means and protocols offer some degree of protection during the transmission and storage of passwords, users are often left unprotected by nothing but security policies and guidelines which are often neglected. Various literatures have shown that users are the ‘weakest link ’ in any password authentication mechanism, due to their propensity to create weak passwords and reuse passwords on multiple accounts. While various identity management solutions have been developed to address the prevalence of users ’ insecure password practices, these solutions still suffer from their own problems and drawbacks. Before we could work towards a more appropriate solution to users ’ insecure password practices, it would be necessary to study the underlying cause of these practices, which lies within users ’ perceptions of their accounts and passwords. In this thesis, we present

Abstract. We introduce Kamouflage: a new architecture for building theft-resistant password managers. An attacker who steals a laptop or cell phone with a Kamouflage-based password manager is forced to carry out a considerable amount of online work before obtaining any user credentials. We implemented our proposal as a replacement for the built-in Firefox password manager, and provide performance measurements and the results from experiments with large real-world password sets to evaluate the feasibility and effectiveness of our approach. Kamouflage is well suited to become a standard architecture for password managers on mobile devices. 1

Abstract. The problem of phishing has attracted considerable attention recently, and a number of solutions and enhanced security measures have been proposed. We perform a detailed analysis of several antiphishing schemes, and attacks and improvements. While several antiphishing technologies address commonly observed phishing tactics, the space evolves rapidly, and a good prevention technique should be robust to anticipated as well as observed attacks. We present a number of attacks and techniques that might be easily employed by phishers and examine the robustness of a recently proposed password re-use antiphishing system. We compare with other proposed phishing prevention techniques and find that it withstands several attacks that render current anti-phishing approaches obsolete and fares better in a large scale deployment than others. 1

Abstract. Proposed in response to the growing number of passwords users have to memorize, password managers allow to store one’s credentials, either on a third-party server (online password manager), or on a portable device (portable password manager) such as a mobile phone or a USB key. In this paper, we present a comparative usability study of three popular password managers: an online manager (LastPass), a phone manager (KeePassMobile) and a USB manager (Roboform2Go). Our study provides valuable insights on average users ’ perception of security and usability of the three password management approaches. We find, contrary to our intuition, that users overall prefer the two portable managers over the online manager, despite the better usability of the latter. Also, surprisingly, our non-technical pool of users shows a strong inclination towards the phone manager. These findings can generally be credited to the fact that the users were not comfortable giving control of their passwords to an online entity and preferred to manage their passwords themselves on their own portable devices. Our results prompt the need for research on developing user-friendly and secure phone managers, owing to the ubiquity of mobile phones. 1

We propose a scheme that exploits scale to prevent phishing. We show that while stopping phishers from obtaining passwords is very hard, detecting the fact that a password has been entered at an unfamiliar site is simple. Our solution involves a client that reports Password Re-Use (PRU) events at unfamiliar sites, and a server that accumulates these reports and detects an attack. We show that it is simple to then mitigate the damage by communicating the identities of phished accounts to the institution under attack. Thus, we make no attempt to prevent information leakage, but we try to detect and then rescue users from the consequences of bad trust decisions. The scheme requires deployment on a large scale to realize the major benefits: reliable low latency detection of attacks, and mitigation of compromised accounts. We harness scale against the attacker instead of trying to solve the problem at each client. In [13] we sketched the idea, but questions relating to false positives and the scale required for efficacy remained unanswered. We present results from a trial deployment of half a million clients. We explain the scheme in detail, analyze its performance, and examine a number of anticipated attacks.

My work involves studying computer security through the lens of security failures. This approach provides unique opportunities to apply advanced ideas from computer science to high-impact practical problems. In one instance, I showed how CDs sold by the world’s largest record company deliberately violated operating system security principles in an attempt to block piracy, rendering PCs on which they were played vulnerable to attack [15]. My findings spurred people to recognize DRM’s (digital rights management’s) potential as a security risk, leading to product recalls, litigation, and changes to U.S. copyright policy, and contributing to the music industry’s retreat from DRM. In another project, the first unrestricted academic study of a touch-screen voting machine, my coauthors and I revealed vulnerabilities worse than even the pessimistic expectations of the security community, including ways that voting machine viruses could change election outcomes [9]. These findings helped shift the national debate on electronic voting, leading a number of states to enact significant changes to their election systems. In these works and in my thesis, I have attempted to make the study of security failures more rigorous. When a bridge collapses, or a ship sinks, or an airliner crashes, scientists and engineers are called upon to rigorously determine the cause. Inquiries into the causes of failure are central to technical progress: they delineate the practical boundaries of what we can achieve with current technology and highlight areas that