ECE Calendar

Abstract:
A key way in which banks mitigate the effects of phishing is to remove fraudulent websites or suspend abusive domain names. This "take-down" is often subcontracted to specialist companies. Prior work has shown that these take-down companies refuse to share their "feeds" of phishing Web site URLs with each other, and consequently, many phishing Web sites are not removed, because the company with the take-down contract remains unaware of their existence. The take-down companies are reluctant to exchange their feeds with each other, fearing that competitors with less comprehensive feeds might "free-ride" off their efforts and stop investing resources to find new websites, as well as use the feeds to poach clients.

To help solve this problem, we propose the Phish-Market protocol, which enables companies with less comprehensive feeds to learn about websites impersonating their own clients that are held by other firms. The protocol is designed so that the contributing firm is compensated only for those websites affecting its competitor's clients and only those previously unknown to the receiving firm. Crucially, the protocol does not reveal to the contributing source which URLs are needed by the receiver, as this is viewed as sensitive information by take-down firms.

The main problem in designing this protocol is making it efficient enough to be used in practice (a naive approach using generic cryptographic techniques would be completely infeasible). I'll describe the ideas behind the cryptographic design and talk a little about our implementation: Using the complete lists of phishing URLs obtained from two large take-down companies, our elliptic-curve-based implementation added a negligible average 5-second delay to securely share URLs.

This is joint work with Tyler Moore.