mind backtrack box center

author : iketut wiratanaya ,translated by Me

Have you make an account at yahoo! Or friendster ? if you have,I bet you have seen like this one :

Just information,this one called Captcha(Completely Automated Public Turing test to tell Computers and Humans Apart) is a program that will test if the user is really human or spam.we have to fill the field the letter at the images.Because the letter on the images only human can read it and not common computer. It makes sense that this program is to prevent spam.

Captcha is usually used for security addition for application like :

1.polling : make sure that who participate at polling is not a bot

2.form filling such as : Form registrasi, form untuk shout box, comment, guest book etc.

3.prevent search engine bot to views private page in your situs.

4.preventing worm and spam.

There are variative used for captcha but the common purpose is to being a gate that only human can pass the required and prevent a bot or spam to pass the required field.commonly captcha is implemented by an word images that has distorted it used to prevent some program to read the word at the images like : OCR(Optical character recognition, is a program to translate a text on images to text)

and how we add captcha at our website..this tutorial will tell you how to add captcha at .jsp website. all you need is only to download this captcha_jsp_code.txt and put it at the page you want to use a captcha.and to show the captcha images the tag is

<img src=”captcha.jsp”>

and last you only have to match up the captcha images and the word that filled by user. like this code

<% String tulisan = (String) session.getAttribute("captcha");
if(input.compareTo(tulisan) != 0)
{
print.out(“success”);
}
else
{
print.out(“failed”); }
%>

note :

The capchat idea is found by Luis von Ahn, Manuel Blum, and Nicholas J. Hopper from Carnegie Mellon University, and John Langford from IBM at 2000.

code source :

http://www.jroller.com/page/mlconnor?entry=simple_captcha_jsp