<?php
// Stegasaurus v.1.9: 
// 		Encrypts a given string with a randomly
//		generated one-time-pad and hides it 
//		inside of a carrier image.
// REQUIRED: PNG Image, PHP >= 4.3.0
// -disruptiv 2007
 
if(isset($_GET['display'])) displayImage($_GET['display']);
if(isset($_GET['dl'])) downloadFile($_GET['dl'], $_GET['dlname']);
 
$submitted = false;						// # Display the forms
$image_url = "http://www.example.com/image.png";
$hideme = "http://www.example.com/somefile.txt";
$key = "7:eXaMpLe";
$newfile = "somefile.txt";
if(isset($_POST['submit'])) {
	$submitted = true;
	$image_url = $_POST['image_url'];
	if(isset($_POST['hideme'])) $hideme = $_POST['hideme'];
	if(isset($_POST['key'])) $key = $_POST['key'];
	if(isset($_POST['newfile'])) $newfile = $_POST['newfile'];
}
echo "<form action='".$_SERVER['PHP_SELF']."' method='post' name='encrypt'>";
echo "<b>ENCRYPT:</b><br><input type='hidden' name='action' value='encrypt'>";
echo "Image: <input type='text' name='image_url' value='$image_url' size=35><br>";
echo "File to Hide: <input type='text' name='hideme' value='$hideme' size=50><br>";
echo "<input type='submit' name='submit' value='Encrypt It'></form><br><br>";
echo "<form action='".$_SERVER['PHP_SELF']."' method='post' name='decrypt'>";
echo "<b>DECRYPT:</b><br><input type='hidden' name='action' value='decrypt'>";
echo "Image: <input type='text' name='image_url' value='$image_url' size=35><br>";
echo "Key: <input type='text' name='key' value='$key' size=35><br>";
echo "New Filename: <input type='text' name='newfile' value='$newfile' size=35><br>";
echo "<input type='submit' name='submit' value='Decrypt It'></form><br><br>";
 
if($submitted) {						// # Encrypt / Decrypt something
	if($_POST['action'] == "encrypt") hideString($_POST['image_url'], $_POST['hideme']);
	else showString($_POST['image_url'], $_POST['key'], $_POST['newfile']);
}
 
// Converts decimal into binary string of a FIXED SIZE
function d2b($var, $len) {
	if($len == 8) $output .= ($var & 128) ? '1' : '0';
	$output .= ($var & 64) ? '1' : '0';
	$output .= ($var & 32) ? '1' : '0';
	$output .= ($var & 16) ? '1' : '0';
	$output .= ($var & 8) ? '1' : '0';
	$output .= ($var & 4) ? '1' : '0';
	$output .= ($var & 2) ? '1' : '0';
	$output .= ($var & 1) ? '1' : '0';
	return $output;
}
 
// Returns random lowercase string
function randomString($length) {
	for($i = 0; $i < $length; $i++) $string .= chr(rand(97,122));
	return $string;
}
 
// Return an array of rgb values for each pixel
function getPixels($image, $width, $height) {
	for($y = 0; $y < $height; $y++) {
		for($x = 0; $x < $width; $x++) {
			$pixels[] = imagecolorsforindex($image, imagecolorat($image, $x, $y));
		}
	}
	return $pixels;
}
// Saves an image created from $newPixels
function savePixels($newPixels, $width, $height, $filename) {
	$curx = 0;
	$cury = 0;
	$image = imagecreatetruecolor($width, $height);
	foreach($newPixels as $pixel) {
		if($curx > $width-1) {
			$cury++;
			$curx = 0;
		}
		if($cury > $height-1) break 2;
		$color = imagecolorallocate($image, $pixel["red"], $pixel["green"], $pixel["blue"]);
		imagesetpixel($image, $curx, $cury, $color);
		$curx++;
	}
	imagepng($image, $filename);
}
 
// Replace the 3 least significant image bits
// With the 3 most significant string bits
function hideBits($pixels, $hideString) {
	$colors = array("red", "green", "blue");
	$imagelen = count($pixels);
	$stringlen = strlen($hideString);
	for($i = 0; $i < $stringlen; $i++) $binstr .= d2b(ord($hideString[$i]), 7);
	$stringlen *= 7;
	$curpixel = 0;
	$curcolor = 0;
	$curbit = 0;
	for($i = 0; $i < $stringlen; $i++) {
		if($curpixel > $imagelen) {
			echo "<br><font color='red'>FATAL ERROR:</font> Hidden data is larger than image can hide";
			die;
		}		
		if($curbit == 3) {
			$curbit = 0;
			$curcolor++;
		}
		if($curcolor == 3) {
			$curcolor = 0;
			$curpixel++;
		}
		$binpixel = d2b($pixels[$curpixel][$colors[$curcolor]], 8);
		$binpixel[strlen($binpixel)-(1+$curbit)] = $binstr[$i];
		$pixels[$curpixel][$colors[$curcolor]] = bindec($binpixel);
		$curbit++;
	}
	return $pixels;
}
// Combine the 3 least significant bits of an image to form a string
function showBits($pixels, $hidelen) {
	$colors = array("red", "green", "blue");
	$imagelen = count($pixels);
	$hidelen *= 7;
	$curpixel = 0;
	$curcolor = 0;
	$curbit = 0;
	for($i = 0; $i < $hidelen; $i++) {
		if($curpixel > $imagelen) {
			echo "<br><font color='red'>FATAL ERROR:</font> Hidden data is larger than image can hide";
			die;
		}
		if($curbit == 3) {
			$curbit = 0;
			$curcolor++;
		}
		if($curcolor == 3) {
			$curcolor = 0;
			$curpixel++;
		}
		$binpixel = d2b($pixels[$curpixel][$colors[$curcolor]],8);
		$binstr .= $binpixel[strlen($binpixel)-(1+$curbit)];
		$curbit++;
	}
	for($i = 0; $i < $hidelen; $i+=7) $string .= chr(bindec(substr($binstr, $i, 7)));
	return $string;
}
 
function displayImage($imagepath) {
	header("Content-type: image/png");
	echo file_get_contents($imagepath);
	unlink($imagepath);
	die;
}
function downloadFile($filepath, $dlname) {
	header("Content-type: application/octet-stream");
	header("Content-length: ".filesize($filepath));
	header("Content-disposition: attachment; filename=\"".$dlname."\";");
	$file = fopen($filepath, "rb");
	echo fread($file, filesize($filepath));
	fclose($file);
	unlink($filepath);
	die;
}
 
function hideString($imagepath, $hidemepath) {
	$image = imagecreatefrompng($imagepath);
	$width = imagesx($image);
	$height = imagesy($image);
	$pixels = getPixels($image, $width, $height);
 
	$file = @fopen($hidemepath, "rb");
	if(!$file) {
		echo "<br><font color='red'>FATAL ERROR:</font> Can't open file <i>$hideme</i><br>";
		die;
	}
	while(!feof($file)) $hideme .= fread($file, 8192);
	fclose($file);
 
	$hiddenlen = strlen($hideme);	
	$key = randomString($hiddenlen);
	for($i = 0; $i < $hiddenlen; $i++) $xored .= $hideme[$i] ^ $key[$i];
	$hideme = base64_encode($xored);
	$hiddenlen = strlen($hideme);
 
	$pixels = hideBits($pixels, $hideme);
	$filename = randomString(8).".png";
	savePixels($pixels, $width, $height, $filename);
	echo "<br><B>Key:</B><br><textarea style='overflow:visible;width:100%;'>".$hiddenlen.':'.$key."</textarea><br>";
	echo "<b><font color='blue'>Stego-Image:</font></b><br>";
	echo "<img src='".$_SERVER['PHP_SELF']."?display=".$filename."'><br>";
}
function showString($imagepath, $key, $dlname) {
	$image = @imagecreatefrompng($imagepath);
	if(!$image) {
		echo "<br><font color='red'>FATAL ERROR:</font> Can't open image <i>$imagepath</i><br>";
		die;
	}
	$width = imagesx($image);
	$height = imagesy($image);
	$pixels = getPixels($image, $width, $height);
 
	list($hiddenlen,$key) = explode(":", $key);
	$keylen = strlen($key);
	$hidden = base64_decode(showBits($pixels, $hiddenlen));
	for($i = 0; $i < $keylen; $i++) $xored .= $hidden[$i] ^ $key[$i];
 
	$filename = randomString(8);
	$file = fopen($filename, "wb");
	fwrite($file, $xored, $keylen);
	echo "<iframe src='".$_SERVER['PHP_SELF']."?dl=".$filename."&dlname=".$dlname."' style='display:none'><br>";
}
?>