Document Type

Technical Report

Publication Date


Technical Report Number



The security of the vast majority of ``secure'' Web services rests on SSL server PKI. However, this PKI doesn't work if the the adversary can trick the browser into appearing to tell the user the wrong thing about the certificates and cryptography. The seminal web spoofing work of Felten et al demonstrated the potential, in 1996, for malicious servers to impersonate honest servers. Our recent follow-up work explicitly shows how malicious servers can still do this---and can also forge the existence of an SSL session and the contents of the alleged server certificate. This paper reports the results of our work to systematically defend against Web spoofing, by creating a trusted path from the browser to the user. Starting with the Mozilla source, we have implemented techniques that protect a wide variety of browser-user communications, that require little participation by the user and minimal disruption of the displayed server content. We have prepared shell scripts that install these modifications on the Mozilla source, to enable others to replicate this work. In on-going work, we are cleaning up and fine-tuning our code. In future work, we hope to examine more deeply the role of user interfaces in enabling users to make effective trust judgments.