supercala

Posted: **Thu Apr 07, 2011 1:04 pm**

Sometimes regular web users find folders you don't want them to, or have bot link to images they somehow find a reference to, and you cannot protect your images or other files if you haven't set your apache server settings to not allow hotlinking etc.

A very good way to stop this from happening is add another layer of security by encrypting the jpg or other file with a password key using basic encryption routines. Here I have written both encryption and decryption examples. You have to make the first file yourself, ex1.jpg etc, but you get the idea.

Code: Select all

<?php
/*
encryptK.php by Kristoffe Brodeur. ©2011 All Rights Reserved.
04-05-2011
*/
//-----
function encrypt($origStr,$eKey,$disp=false)
	{
	$encStr="";
	$lenO=strlen($origStr);
	//
	for($e=0;$e<$lenO;$e++)
		{
		$origC=substr($origStr,$e,1);
		$currKeyChr=substr($eKey,($e%strlen($eKey))-1,1);
		$newC=chr(ord($origC)+ord($currKeyChr));
		$encStr.=$newC;
		}
	//
	if($disp===true)
		{
		echo "[end]$encStr<br>";
		echo "[end]".base64_encode($encStr)."<br>";
		}
	return base64_encode($encStr);
	}
//-----
function decrypt($encStr,$eKey,$disp=false)
	{
	$decStr="";
	$encStr=base64_decode($encStr);
	$lenO=strlen($encStr);
	//
	if($disp==true)
		{
		echo "decrypt[$encStr]<br>";
		}
	//
	for($e=0;$e<$lenO;$e++)
		{
		$origC=substr($encStr,$e,1);
		$currKeyChr=substr($eKey,($e%strlen($eKey))-1,1);
		$newC=chr(ord($origC)-ord($currKeyChr));
		$decStr.=$newC;
		}
	return $decStr;
	}
//-----
function encFile($fileO,$fileE,$key)
	{
	//
	if(file_exists($fileO))
		{
		echo "[orig jpg]$fileO<br>";
		$fileStr=file_get_contents($fileO);
		$encStr=encrypt($fileStr,$key);
		//
		if($encFile=fopen($fileE,"c"))
			{
			file_put_contents($fileE,$encStr);
			fclose($fileE);
			return true;
			}
		else
			{
			return false;
			}
		}
	else
		{
		return false;
		}
	}
//-----
function decFile($fileE,$fileD,$key)
	{
	//
	if(file_exists($fileE))
		{
		$fileStr=file_get_contents($fileE);
		$decStr=decrypt($fileStr,$key);
		//
		if($decFile=fopen($fileD,"c"))
			{
			file_put_contents($fileD,$decStr);
			fclose($decFile);
			return true;
			}
		else
			{
			return false;
			}
		}
	else
		{
		return false;
		}
	}
//-----
$testKey="y6u6";
$testStr="abcdefghijklmnopqrstuvwxyz";
$testEncStr=encrypt($testStr,$testKey,true);
$testDecStr=decrypt($testEncStr,$testKey,true);
//
encFile("orig.jpg","enc.jpg",$testKey);
decFile("enc.jpg","dec.jpg",$testKey);
?>

<html>
	<body>
	<hr />
	[orig]<?php echo $testStr;?><br>
	[enc]<?php echo $testEncStr;?><br>
	[dec]<?php echo $testDecStr;?><br>
	
	<h3>Jpg encode | decode test</h3>
	<p>To start this program, you will need to make a jpg image and call it 'orig.jpg' in the same folder as this file as a test.</p>
	<p>The original jpg is encrypted with the password, and then saved encoded.  It will never read and will look like a bad file even to those with access to a hidden folder.  Only with the decode process and a key will the viewer allow the decoded jpg.  A great use is to not write to the server, but send a mime type jpg that reads and decodes the image back to the php request so it is totally dynamic.</p>
	
	<table>
		<tr>
			<td valign="top">[orig]<br><img src="orig.jpg" width="400px" /></td>
			<td valign="top">[enc]<br><img src="enc.jpg" width="400px" /></td>
			<td valign="top">[dec]<br><img src="dec.jpg" width="400px" /></td>
		</tr>
	</table>
	</body>
</html>

supercala

jpg file encryption decryption with password and base64

jpg file encryption decryption with password and base64