Captchas With a Purpose

In this paper, we develop some new Captchas belonging to genre — “CAPTCHAs with a purpose.” These CAPTCHAs apart from having its applications serve some useful purpose. reCAPTCHA is one such Captcha developed at Carnegie Mellon University. It helps to digitize books. Another such Captcha is Asirra developed at Microsoft which provides homes for homeless animals. In this paper, we present Time based, Sentence based, Human Emotion based CAPTCHAs which have range of other useful purpose such as measuring reaction time of people, promoting news, general knowledge facts, jokes among people while engaging in routine activities such as checking email. Also, one can be used for conducting online polls on a very large scale. We also showcase a New Game with a Purpose called “Identical Emotions” which helps to assign tags describing emotions depicted by the images, to varied images. It can also be used to serve Emotion Based CAPTCHA. We also present a new scheme which renders attack on CAPTCHAs useless and make old CAPTCHAs reusable and help in using CAPTCHAs which might serve some practical purpose which otherwise might be vulnerable to use. This system also enables to use different CAPTCHAs with a purpose in conjunction with each other. At present most websites deploy only a single algorithm reCAPTCHA whose practical purpose is to digitize books, thus is limited to one domain. This system can thus, broaden the application domain of CAPTCHAs.