| Abstract
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A large number of user PCs are currently infected with different types of malicious software including spyware, keyloggers, and rootkits. In general, any Internet-connected end-host cannot be fully trusted. In addition to this compromised host problem, attacks exploiting usability drawbacks of web services and security tools when used by everyday users, and semantic attacks such as phishing are commonly observed. In the given untrusted environment, traditional threat models which assume trusted end-hosts need to be re-evaluated. We propose a number of techniques to improve the trustworthiness of the web considering the current untrusted environment. To understand what is expected from regular users for performing sensitive online tasks, we review security requirements of six Canadian online banks, and identified an emerging gap between these requirements and usability. Instead of requiring users to follow an extensive list of security best-practices for online banking, we propose the Mobile Password Authentication (MP-Auth) protocol. Using a trusted personal device (e.g., cellphone) in conjunction with a PC, MP-Auth protects a user's long-term login credentials, and offers transaction integrity assuming the user PC is untrustworthy and the user is unaware of phishing attacks. MP-Auth's security largely depends on user-chosen passwords, which are generally weak . To assist users in generating strong but usable passwords, we propose an Object-based Password (ObPwd) scheme which creates text passwords from user-selected objects, e.g., photos or music files. As part of the compromised host problem, we further assume that sensitive identity numbers (e.g., Social Insurance Number) will eventually be breached. To reduce. the value of compromised credential information to attackers in such a scenario, we propose the use of localized ID numbers that are valid only for a particular relying party. A similar localization approach for banking PINs to prevent exploitation of compromised PINs from intermediate banking switches is also proposed.
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