Some time ago read some of the verification code of the article, that is, a series of randomly generated numbers or symbols, create a picture, the picture with some interference pixels (to prevent OCR), by the user's naked eye identification of the verification code information, the input form submitted to the site verification, verification success to use a function.
An article also briefly describes the implementation of the method, as follows:
Code One:
/*
* Filename:authpage.php (as the current mainstream development language)
* Author:hutuworm
* date:2003-04-28
* @Copyleft hutuworm.org
*/
Srand (Double) microtime () *1000000);
Verify that the user input is consistent with the verification code
if (Isset ($HTTP _post_vars[authinput))
{
if (strcmp ($HTTP _post_vars[authnum], $HTTP _post_vars[authinput]) ==0)
echo "Verified success! ";
Else
echo "Verification failed! ";
}
Generate a new four-bit integer verification code
while (($authnum =rand ()%10000) <1000);
?>
Code two:
/*
* Filename:authimg.php (as the current mainstream development language)
* Author:hutuworm
* date:2003-04-28
* @Copyleft hutuworm.org
*/
Generate a Captcha picture
Header ("Content-type:image/png");
Srand (Double) microtime () *1000000);
$im = Imagecreate (58,28);
$black = Imagecolorallocate ($im, 0,0,0);
$white = Imagecolorallocate ($im, 255,255,255);
$gray = Imagecolorallocate ($im, 200,200,200);
Imagefill ($im, 68,30, $gray);
Drawing a four-bit integer verification code into a picture
Imagestring ($im, 5, 8, $HTTP _get_vars[authnum], $black);
for ($i =0; $i <50; $i + +)//Add interfering pixels
{
Imagesetpixel ($im, Rand ()%70, Rand ()%30, $black);
}
Imagepng ($im);
Imagedestroy ($im);
?>
This program has basically achieved the verification code generation and verification function, but the article author does not know why the content of the verification code is displayed in the form, so that, only restricts the user must enter the verification code, the malicious program has no preventive effect. Can be said to be difficult for people, rather than to guard against attacks.
But fortunately, according to the original author's ideas, we can save the validation string in the session, so that it has a certain degree of security.
The code is as follows:
File:authform.php (as the current mainstream development language)
/*
* "Filename:authimg.php (as the current mainstream development language)
*/
Header ("Content-type:image/png");
Session_Start ();
$auth _num= "";
Session_register (Auth_num);
$im =imagecreate (63,20);
Srand (Double) microtime () *1000000);
$auth _num_k=md5 (rand (0,9999));
$auth _num=substr ($auth _num_k,17,5);
$black =imagecolorallocate ($im, 0,0,0);
$white =imagecolorallocate ($im, 255,255,255);
$gray =imagecolorallocate ($im, 200,200,200);
Imagefill ($im, 63,20, $black);//This line does not know why in my company's server error, change a space ok
Imagestring ($im, 5,10,3, $auth _num, $gray);
for ($i =0; $i <200; $i + +)
{
$randcolor =imagecolorallocate ($im, Rand (0,255), Rand (0,255), Rand (0,255));
Imagesetpixel ($im, Rand ()%70,rand ()%30, $randcolor);
}
Imagepng ($im);
Imagedestroy ($im);
?>
/*
* Filename:authpage.php (as the current mainstream development language)
http://www.bkjia.com/PHPjc/508612.html www.bkjia.com true http://www.bkjia.com/PHPjc/508612.html techarticle some time ago read some of the verification code of the article, that is, a series of randomly generated numbers or symbols, create a picture, the picture with some interference pixels (to prevent OCR), by the user meat ...
