By matto3c
via codegravity.com
Published: Aug 08 2007 / 15:09
New version features a better way of rendering the expression that user has to evaluate. The numbers consist of 3x5 random character matrix. MathGuard is free PHP class that everyone can use as anti-spam protection for the website forms. It's also a suitable solution when there is no PHP GD support from the webhosting company. Read also user testimonials.
SaveShareSend
Tags: announcement, open source, php, security
Comments
FlySwat replied ago:
This is a step backwards in anti-spam technology.
You have essentially taken a capta, and reduced it into a low resolution image based upon a format that is exceptionally easy to parse. All a spammer would have to do is construct a regular expression that would convert your formatted HTML back into its numeric equivalent and perform the calculation.
While this would be a fair bit of work, it is far easier than creating a OCR system to recognize a captcha, and people have created those.
stamonitu replied ago:
determine the rank, eigenvalues, determinant, inverse, transpose
jcarrascal replied ago:
This isn't secure at all. It uses a 3x5 matrix for each character that can be easily looked up in an array and after that a call to eval() will give you the correct answer. Don't use it on your site in it's present state.
Voters For This Link (6)
Voters Against This Link (7)