inc/form_security.php

<?php
/*
 * Name: form_security.php
 * Function: contains routines created to stop people from using 'bots' to auto complete the forms with spam info.
 * I/O: functions take various parmaters, Some return values.
 * By: M. Ward
 * 
 */
 
/**************************************
* 
* Name: SecureQuestion
* Function: This function generates a relatively random mathematical question and prints it to the bottom 
* of the calling page.
* I/O: takes a param for where html output should go, and returns the 'result' of the question for comparison.
* Date: Nov 21/05
* By: M. Ward
* 
***************************************/
function SecureQuestion( &$html ) {
  //get the  3 values and 2 functions
  $Security_Values = array(mt_rand(1,100), mt_rand(1,100), mt_rand(1,100), mt_rand(0,1),mt_rand(0,1) );
  //sort out the operators
  $Operators = array('+','-');
          
  //set the entry form and question into the html output
  $html .= "<tr><td colspan=\"2\"><font face=\"Arial\" color=\"#FF0000\">*</font>Please enter the result of the following Mathematical question: ";
  $html .= $Security_Values[0] . $Operators[$Security_Values[3]] . $Security_Values[1] . $Operators[$Security_Values[4]] . $Security_Values[2];
  $html .= "<br /></td></tr> <tr><td colspan=\"2\"><input type=\"text\" size=\"6\" name=\"SkillAnswer\"></td></tr>";
            
  //compute the result the hard way.
  if ( $Security_Values[3] == 0)
    $Result = $Security_Values[0] + $Security_Values[1];
  else
    $Result = $Security_Values[0] - $Security_Values[1];
  if ( $Security_Values[4] == 0)
    $Result = $Result + $Security_Values[2];
  else
    $Result = $Result - $Security_Values[2];
            
            
  return( CryptResult($Result) );
	
}

/*********************************************
 *
 * Name: CryptResult
 * Function:  encrypts(cheaply I might add) the passed int and returns the 'encrypted' result
 * I/O: Takes the number to be encrypted and returns the encrypted data
 * Date: Nov 23/05
 * By: M. Ward
 * 
 * ********************************************/
function CryptResult( $key ) {
  
  //first step
  $crypt = $key - 83817;
  //second step
  $crypt = $crypt + 262237125;
  
  //now serialise the data
  $crypt = serialize($crypt);
  
  //prep for storage
  $crypt = base64_encode($crypt);
  
  //return value
  return $crypt;
 	
}

/*********************************************
 *
 * Name: DeCryptResult
 * Function:  Decrypts(cheaply I might add) the passed int and returns the 'clear' result
 * I/O: Takes the number to be decrypted and returns the clear data
 * Date: Nov 23/05
 * By: M. Ward
 * 
 * ********************************************/
function DecryptResult( $key ) {
  
  //first step decode
  $clear= base64_decode($key);
  //second step unserialize
  $clear = unserialize($clear);
  
  //now backout the math
  $clear = $clear - 262237125;
  
  //last step
  $clear = $clear + 83817;
  
  //return value
  return $clear;
 	
}
 

?>