SD-CAPTCHA: An Alternate to Authentication System

Captcha stands for completely automated program to tell computer and human are apart. This captcha system is not a new concept it's being used by number of online service providers such as Google, Yahoo etc. but these captcha are highly sophisticated and sometime user gets annoyed to get rid of it. The prime task of Captcha is to differentiate computer from human and with the advent of technology and attacks the captchas are getting more secure and stronger day by day, with time usability or friendliness is reduced leaving user annoyed because machine passes the captcha test but user yet messing up with the captcha to pass. In this paper a standalone developed captcha design is proposed which is not only secured but also it is user friendly. A basic attack was made to check the resistance of SD-CAPTCHA which gives results lesser then 55%, because the robustness of a text CAPTCHA is typically determined by the strength of its segmentation-resistance mechanism.