Abstract: There are several texts based and graphical password techniques based which are being used for user authentication. In current scenario many of the applications being developed for user authentication are text based password. Text passwords are comparably not secured as the graphical passwords because text passwords easily suffer from man attacks like shoulder suffering, dictionary attacks and many more. They can be easily breached with number of different techniques. The textual passwords will be either alphabetic, numeric or alphanumeric type (i.e. combination of alphabets as well as numbers and special characters). The research shows that text passwords are complex and hard to remember and hence humans select a short password which is simple in some manner to memorize and recall. As a result the security is not so accurate in the present scenario. In our system we are proposing the enhanced security by Captcha technology in which the images are fixed and the texts called Captcha are changed every time and hence it is more secure than traditional technique. By using graphical password system and Captcha technology a new security primitive will be introduced. In this system the watermarking method will be used in database to hide the actual images by simple codes. Working of the system will be done through, user need to register first and then selects number of images as a password after that while login user needs to enter the random code generated by the previously selected images as password an access his account by this system. In a case, if user forgets the password then user will be able to recover the account by a secure provision. And hence the security will increase automatically than traditional password entering techniques because user need to enter different set of codes every time while login. It means there is no need to remember the complex and difficult textual passwords. Instead of that user need to just identify the image and enter the codes below that image. By this technique we will try to upgrade to the existing security for better and secure password based systems.
Keywords: Authentication, Captcha, Digital Images, Graphical password, Watermarking.