Public Key-Embedded Graphic CAPTCHAs

Abstract

In this paper, we introduce the concept of Public-Key embedded Graphic CAPTCHAs and their usage as an Anti-Phishing mechanism. These CAPTCHAs contain a user-specific image object and a pattern (for e.g. a sub-string) of a secure channel invariant (for e.g. the Public-key of the authentic web-server), wherein the image object and pattern are linked. By virtue of a built-in one/two-way implicit challenge mechanism and this verifiable association between the image object and the specific sub-pattern of the Public Key, they help in detecting/resisting automated or human-assisted Phishing attacks.