Client Login:	Home

D2 CAPTCHA

D2 Captcha is a free ASP.NET application which allows you to easily add a CAPTCHA (Completely Automated Public Turing test to tell Computers and Humans Apart.) image to your web forms.

What is CAPTCHA and why do i need it?

A CAPTCHA is a challenge-response test designed to ensure that your web forms are being submitted by a human and not a computer or bot. It is used to prevent automated software from performing actions which degrade the quality of service of a given system, whether due to abuse or resource expenditure. An example would be an automated application that creates accounts on your forum/website or attempts to use your email contact forms or feedback forms.

Whilst not infallible, CAPTCHA images add an extra level of protection to make your site less attractive as a target.

Download D2 CAPTCHA for free:

Example and Installation:

To download the application click the link below. Note, this is a free application, provided as-is, without warranty and support.

Download D2 CAPTCHA

System Requirements:

D2 CAPTCHA is an ASP.NET based application and requires that your site is running on .NET 2.0 or greater.

Example user submission form
Your Name:
Telephone:
Please copy the characters you see below into the textbox. If you cannot read the characters then refresh the page to generate a new image:

To integrate D2 CAPTCHA within your own web forms:

D2 CAPTCHA is an ASP.NET application and requires that your site is based on .NET 2.0 or greater.

To use D2 CAPTCHA within your own website first copy the D2CAPTCHA.dll file to your sites 'bin' folder. Also copy the D2captcha.ashx to your sites main directory.

To add CAPTCHA functionality to your form just include code similar to the inline code included in the example.aspx file, note the 'Protected Sub Button1_Click' event code for details of how to check the user has input the correct string.

To configure D2 CAPTCHA:

There are several configurable parameters to allow you to alter the display of D2 CAPTCHA. These are set by editing the variables within the D2captcha.ashx file.

******************************
- Dim NumberCount As Integer = 5

This is the number of characters displayed to the users eg:

5:

********************************

- CAPTCHAWidth As Integer = 135

Width of CAPTCHA image in pixels

********************************

- CAPTCHAHeight As Integer = 35

Height of CAPTCHA image in pixels

*******************************

- Dim CAPTCHAGradColor As String = "Linen"

Colour of gradient fill, use standard HTML colour names eg:

Silver:

MediumOrchid:

BurlyWood:

******************************

- Dim NumbersOrLetters As Integer = 1

Use either numeric 123 characters or alphabetic abc characters eg:

********************************

- Dim AddCurve As Integer = 0

Draw an aditional random curve on the image to provide more protection from OCR (but also makes it harder for human readers!) eg:

********************************

For best results, we recommend you leave the settings at default.

NOTE: D2 CAPTCHA is a free application provided as-is and without any warranty or support. You use it at your own risk and D2 Computing Ltd do not provide or imply any guarantee of functionality. Whilst we will not reply to any support requests for this application, you are welcome to post any question or comments in our forum at: http://forum.d2sitelock.com.

http://www.d2computing.co.uk