Balancing Usability and Security in a Video CAPTCHA
Venue
Proceedings of the 5th Symposium on Usable Privacy and Security (SOUPS '09), ACM Press (2009)
Publication Year
2009
Authors
Kurt Alfred Kluever, Richard Zanibbi
BibTeX
Abstract
We present a technique for using a content-based video labeling task as a CAPTCHA.
Our video CAPTCHAs are generated from YouTube videos, which contain labels (tags)
supplied by the person that uploaded the video. They are graded using a video's
tags, as well as tags from related videos. In a user study involving 184
participants, we were able to increase the average human success rate on our video
CAPTCHA from roughly 70% to 90%, while keeping the average success rate of a tag
frequency-based attack fixed at around 13%. Through a different parameterization of
the challenge generation and grading algorithms, we were able to reduce the success
rate of the same attack to 2%, while still increasing the human success rate from
70% to 75%. The usability and security of our video CAPTCHA appears to be
comparable to existing CAPTCHAs, and a majority of participants (60%) indicated
that they found the video CAPTCHAs more enjoyable than traditional CAPTCHAs in
which distorted text must be transcribed.
