• NS.SUDHAKARAN
• K.MAGESHWAR
• G.GNANAKUMAR

Captcha is a security mechanism designed to differ-entiate between computers and humans, and is used to defend against malicious bot programs. Text-based Captchas are the most widely deployed differentiation mechanism, and almost all text-based Captchas are single-layered. Numerous successful at-tacks on the single-layer text-based Captchas deployed by Google, Yahoo! and Amazon have been reported. In new two-layer Captcha scheme was deployed in 2015 by microsoft. This appears to be the first application of two-layer Captchas. It is therefore natural to ask a fundamental question: is the two-layer Captcha as secure as its designers expected? Intrigued by this question, we have for the first time systematically analyzed the security of the two-layer Captcha in this paper.

Four Factor Authentication System Text Based Graphical Password Scheme Using Machine Learning

"Four Factor Authentication System Text Based Graphical Password Scheme Using Machine Learning", International Journal of Emerging Technologies and Innovative Research (www.jetir.org), ISSN:2349-5162, Vol.5, Issue 3, page no.659-663, March-2018, Available :http://www.jetir.org/papers/JETIR1803118.pdf

"Four Factor Authentication System Text Based Graphical Password Scheme Using Machine Learning", International Journal of Emerging Technologies and Innovative Research (www.jetir.org | UGC and issn Approved), ISSN:2349-5162, Vol.5, Issue 3, page no. pp659-663, March-2018, Available at : http://www.jetir.org/papers/JETIR1803118.pdf