Blame - www/cipher.html - platform/external/ImageMagick

blob: 25467702cc77b03a216bb62ce004c6d8c54bb2b8 [file] [log] [blame]

cristy	3eaa0ef	2010-03-06 20:35:26 +0000	[diff] [blame]	1
cristy	dcca3fa	2010-12-29 21:50:07 +0000	[diff] [blame]	2	<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
				3	"http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
cristy	2bd2a98	2011-02-15 00:52:58 +0000	[diff] [blame]	4	<html version="-//W3C//DTD XHTML 1.1//EN"
				5	xmlns="http://www.w3.org/1999/xhtml" xml:lang="en"
				6	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
				7	xsi:schemaLocation="http://www.w3.org/1999/xhtml
				8	http://www.w3.org/MarkUp/SCHEMA/xhtml11.xsd">
cristy	3eaa0ef	2010-03-06 20:35:26 +0000	[diff] [blame]	9	<head>
cristy	3c98a4f	2010-08-13 20:09:41 +0000	[diff] [blame]	10	<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/>
				11	<meta name="verify-v1" content="g222frIIxcQTrvDR3NBRUSKP3AnMNoqxOkIniCEkV7U="/>
cristy	ffb69ed	2010-12-25 00:06:48 +0000	[diff] [blame]	12	<title>ImageMagick: Encipher or Decipher an Image</title>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	13	<meta http-equiv="Content-Language" content="en-US"/>
				14	<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
				15	<meta http-equiv="Reply-to" content="magick-users@imagemagick.org"/>
cristy	3c98a4f	2010-08-13 20:09:41 +0000	[diff] [blame]	16	<meta name="Application-name" content="ImageMagick"/>
cristy	e6e8415	2011-06-06 14:16:49 +0000	[diff] [blame]	17	<meta name="Description" content="Use ImageMagick to convert, edit, or compose bitmap images in a variety of formats. In addition resize, rotate, shear, distort and transform images automagically."/>
cristy	3c98a4f	2010-08-13 20:09:41 +0000	[diff] [blame]	18	<meta name="Application-url" content="http://www.imagemagick.org"/>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	19	<meta name="Generator" content="PHP"/>
cristy	e6e8415	2011-06-06 14:16:49 +0000	[diff] [blame]	20	<meta name="Keywords" content="encipher, or, decipher, an, image, ImageMagick, ImageMagic, MagickCore, MagickWand, PerlMagick, Magick++, RMagick, PythonMagick, JMagick, TclMagick, Image, Magick, Magic, Wand, ImageMagickObject, Image, Processing, Automagically"/>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	21	<meta name="Rating" content="GENERAL"/>
				22	<meta name="Robots" content="INDEX, FOLLOW"/>
				23	<meta name="Generator" content="ImageMagick Studio LLC"/>
				24	<meta name="Author" content="ImageMagick Studio LLC"/>
				25	<meta name="Revisit-after" content="2 DAYS"/>
				26	<meta name="Resource-type" content="document"/>
cristy	7e41fe8	2010-12-04 23:12:08 +0000	[diff] [blame]	27	<meta name="Copyright" content="Copyright (c) 1999-2011 ImageMagick Studio LLC"/>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	28	<meta name="Distribution" content="Global"/>
cristy	dcca3fa	2010-12-29 21:50:07 +0000	[diff] [blame]	29	<link rel="icon" href="../images/wand.png"/>
cristy	3c98a4f	2010-08-13 20:09:41 +0000	[diff] [blame]	30	<link rel="shortcut icon" href="../images/wand.ico" type="images/x-icon"/>
				31	<link rel="meta" type="application/rdf+xml" title="ICI" href="http://imagemagick.org/ici.rdf"/>
cristy	7a40ba8	2011-01-08 20:31:18 +0000	[diff] [blame]	32	<link rel="stylesheet" href="http://www.google.com/cse/style/look/default.css" type="text/css" />
cristy	3c98a4f	2010-08-13 20:09:41 +0000	[diff] [blame]	33	<style type="text/css" media="all">
				34	@import url("../www/magick.css");
				35	</style>
cristy	dcca3fa	2010-12-29 21:50:07 +0000	[diff] [blame]	36	<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.4/jquery.min.js"></script>
cristy	361f466	2010-12-31 23:02:52 +0000	[diff] [blame]	37	<script type="text/javascript" src="../fancybox/jquery.fancybox-1.3.4.pack.js"></script>
				38	<link rel="stylesheet" type="text/css" href="../fancybox/jquery.fancybox-1.3.4.css" media="screen" />
				39	<script type="text/javascript">
				40	$(document).ready(function() {
				41	$("a[href$=.jpg],a[href$=.png],a[href$=.gif]").fancybox({
				42	'transitionIn' : 'elastic',
				43	'transitionOut' : 'elastic',
				44	'overlayShow' : false,
				45	'opacity' : true
				46	});
				47	});
				48	</script>
cristy	3eaa0ef	2010-03-06 20:35:26 +0000	[diff] [blame]	49	</head>
				50
				51	<body id="www-imagemagick-org">
				52	<div class="titlebar">
cristy	b52981c	2011-03-19 17:09:31 +0000	[diff] [blame]	53	<div style="margin: 17px auto; float: left;">
				54	<script type="text/javascript">
				55	<!--
				56	google_ad_client = "pub-3129977114552745";
				57	google_ad_slot = "5439289906";
				58	google_ad_width = 728;
				59	google_ad_height = 90;
				60	//-->
				61	</script>
				62	<script type="text/javascript"
				63	src="http://pagead2.googlesyndication.com/pagead/show_ads.js">
				64	</script>
				65	</div>
cristy	3eaa0ef	2010-03-06 20:35:26 +0000	[diff] [blame]	66	<a href="http://www.imagemagick.org/discourse-server/">
cristy	af8d665	2011-02-04 21:57:45 +0000	[diff] [blame]	67	<img src="../images/logo.jpg"
				68	alt="ImageMagick Logo"
cristy	178edaf	2011-01-23 03:42:39 +0000	[diff] [blame]	69	style="width: 123px; height: 118px; border: 0px; float: right;" /></a>
cristy	3eaa0ef	2010-03-06 20:35:26 +0000	[diff] [blame]	70	<a href="../index.html">
cristy	af8d665	2011-02-04 21:57:45 +0000	[diff] [blame]	71	<img src="../images/sprite.jpg"
				72	alt="ImageMagick Sprite"
cristy	3eaa0ef	2010-03-06 20:35:26 +0000	[diff] [blame]	73	style="width: 114px; height: 118px; border: 0px; float: right;" /></a>
				74	</div>
				75
cristy	ce69bb0	2010-07-27 19:49:46 +0000	[diff] [blame]	76	<div class="westbar">
cristy	3eaa0ef	2010-03-06 20:35:26 +0000	[diff] [blame]	77
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	78	<div class="menu">
cristy	83a272e	2010-05-07 20:40:35 +0000	[diff] [blame]	79	<a title="About ImageMagick" href="../index.html">About ImageMagick</a>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	80	</div>
cristy	3eaa0ef	2010-03-06 20:35:26 +0000	[diff] [blame]	81	<div class="sep"></div>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	82	<div class="menu">
cristy	bb50337	2010-05-27 20:51:26 +0000	[diff] [blame]	83	<a title="Binary Releases" href="../www/binary-releases.html">Binary Releases</a>
				84	</div>
				85	<div class="sub">
				86	<a title="Binary Release: Unix" href="../www/binary-releases.html#unix">Unix</a>
				87	</div>
				88	<div class="sub">
				89	<a title="Binary Release: MacOS X" href="../www/binary-releases.html#macosx">Mac OS X</a>
				90	</div>
				91	<div class="sub">
cristy	e6e8415	2011-06-06 14:16:49 +0000	[diff] [blame]	92	<a title="Binary Release: iOS" href="../www/binary-releases.html#iOS">iOS</a>
cristy	da16f16	2011-02-19 23:52:17 +0000	[diff] [blame]	93	</div>
				94	<div class="sub">
cristy	bb50337	2010-05-27 20:51:26 +0000	[diff] [blame]	95	<a title="Binary Release: Windows" href="../www/binary-releases.html#windows">Windows</a>
				96	</div>
				97	<div class="sep"></div>
				98	<div class="menu">
cristy	83a272e	2010-05-07 20:40:35 +0000	[diff] [blame]	99	<a title="Command-line Tools" href="../www/command-line-tools.html">Command-line Tools</a>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	100	</div>
				101	<div class="sub">
cristy	83a272e	2010-05-07 20:40:35 +0000	[diff] [blame]	102	<a title="Command-line Tools: Processing" href="../www/command-line-processing.html">Processing</a>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	103	</div>
				104	<div class="sub">
cristy	83a272e	2010-05-07 20:40:35 +0000	[diff] [blame]	105	<a title="Command-line Tools: Options" href="../www/command-line-options.html">Options</a>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	106	</div>
				107	<div class="sub">
cristy	83a272e	2010-05-07 20:40:35 +0000	[diff] [blame]	108	<a title="Command-line Tools: Usage" href="http://www.imagemagick.org/Usage/">Usage</a>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	109	</div>
				110	<div class="menu">
cristy	83a272e	2010-05-07 20:40:35 +0000	[diff] [blame]	111	<a title="Program Interfaces" href="../www/api.html">Program Interfaces</a>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	112	</div>
				113	<div class="sub">
cristy	83a272e	2010-05-07 20:40:35 +0000	[diff] [blame]	114	<a title="Program Interface: MagickWand" href="../www/magick-wand.html">MagickWand</a>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	115	</div>
				116	<div class="sub">
cristy	83a272e	2010-05-07 20:40:35 +0000	[diff] [blame]	117	<a title="Program Interface: MagickCore" href="../www/magick-core.html">MagickCore</a>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	118	</div>
				119	<div class="sub">
cristy	83a272e	2010-05-07 20:40:35 +0000	[diff] [blame]	120	<a title="Program Interface: PerlMagick" href="../www/perl-magick.html">PerlMagick</a>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	121	</div>
				122	<div class="sub">
cristy	dcca3fa	2010-12-29 21:50:07 +0000	[diff] [blame]	123	<a title="Program Interface: Magick++" href="../www/magick++.html">Magick++</a>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	124	</div>
cristy	3eaa0ef	2010-03-06 20:35:26 +0000	[diff] [blame]	125	<div class="sep"></div>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	126	<div class="menu">
cristy	83a272e	2010-05-07 20:40:35 +0000	[diff] [blame]	127	<a title="Install from Source" href="../www/install-source.html">Install from Source</a>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	128	</div>
				129	<div class="sub">
cristy	83a272e	2010-05-07 20:40:35 +0000	[diff] [blame]	130	<a title="Install from Source: Unix" href="../www/install-source.html#unix">Unix</a>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	131	</div>
				132	<div class="sub">
cristy	83a272e	2010-05-07 20:40:35 +0000	[diff] [blame]	133	<a title="Install from Source: Windows" href="../www/install-source.html#windows">Windows</a>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	134	</div>
				135	<div class="menu">
cristy	83a272e	2010-05-07 20:40:35 +0000	[diff] [blame]	136	<a title="Resources" href="../www/resources.html">Resources</a>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	137	</div>
cristy	bb50337	2010-05-27 20:51:26 +0000	[diff] [blame]	138	<div class="menu">
				139	<a title="Architecture" href="../www/architecture.html">Architecture</a>
				140	</div>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	141	<div class="menu">
cristy	83a272e	2010-05-07 20:40:35 +0000	[diff] [blame]	142	<a title="Download" href="../www/download.html">Download</a>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	143	</div>
cristy	3eaa0ef	2010-03-06 20:35:26 +0000	[diff] [blame]	144	<div class="sep"></div>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	145	<div class="menu">
cristy	5292344	2011-01-15 22:54:31 +0000	[diff] [blame]	146	<a title="Search" href="../www/search.html">Search</a>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	147	</div>
cristy	3eaa0ef	2010-03-06 20:35:26 +0000	[diff] [blame]	148	<div class="sep"></div>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	149	<div class="menu">
cristy	ffb69ed	2010-12-25 00:06:48 +0000	[diff] [blame]	150	<a title="Site Map" href="../www/sitemap.html">Site Map</a>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	151	</div>
				152	<div class="sub">
cristy	ffb69ed	2010-12-25 00:06:48 +0000	[diff] [blame]	153	<a title="Site Map: Links" href="../www/links.html">Links</a>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	154	</div>
cristy	3eaa0ef	2010-03-06 20:35:26 +0000	[diff] [blame]	155	<div class="sep"></div>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	156	<div class="menu">
cristy	10549a1	2011-05-15 19:04:46 +0000	[diff] [blame]	157	<a rel="follow" title="Sponsors" href="../www/sponsors.html">Sponsors:</a>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	158
cristy	b52981c	2011-03-19 17:09:31 +0000	[diff] [blame]	159	<a href="http://www.networkredux.com">
				160	<img src="../images/networkredux.png" alt="[sponsor]"
				161	style="margin-top: 4px; margin-left: 4px; border: 0px; float: left;" /></a>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	162	<div class="sponsbox">
cristy	178edaf	2011-01-23 03:42:39 +0000	[diff] [blame]	163	<div class="sponsor">
cristy	81492d6	2011-06-07 16:41:42 +0000	[diff] [blame]	164	<a rel="follow" title="Sponsor: Web Hosting" href="http://www.micfo.com">Web Hosting</a><!-- 209901010090s golestan -->
				165	</div>
				166	<div class="sponsor">
cristy	8413418	2011-06-15 22:59:00 +0000	[diff] [blame^]	167	<a rel="follow" title="Sponsor: Search engine optimisation" href="http://www.seomoves.com.au">Search engine optimisation</a><!-- 201110010090s jen@seo lowprofilelinks -->
				168	</div>
				169	<div class="sponsor">
cristy	81492d6	2011-06-07 16:41:42 +0000	[diff] [blame]	170	<a rel="follow" title="Sponsor: Druckerei" href="http://print24.com/de/">Druckerei</a><!-- 201110010720 -->
				171	</div>
				172	<div class="sponsor">
cristy	ba1758d	2011-06-03 01:29:12 +0000	[diff] [blame]	173	<a rel="follow" title="Sponsor: Web Hosting Deals" href="http://www.webhostingdeals.org">Web Hosting Deals</a><!-- 201111010270 chee.hoa darin -->
				174	</div>
				175	<div class="sponsor">
				176	<a rel="follow" title="Sponsor: Web Hosting Reviews" href="http://www.webhostingsecretrevealed.com">Web Hosting Secret Revealed</a><!-- 201204010540 iamchee jerry -->
				177	</div>
				178	<div class="sponsor">
cristy	4bf6e23	2011-05-21 01:43:33 +0000	[diff] [blame]	179	<a rel="follow" title="Sponsor: Web Hosting Break" href="http://www.webhostingbreak.com">Web Hosting Break</a><!-- 201109010090 ian@ian-m... -->
cristy	45dbd32	2011-03-27 16:40:38 +0000	[diff] [blame]	180	</div>
				181	<div class="sponsor">
cristy	10549a1	2011-05-15 19:04:46 +0000	[diff] [blame]	182	<a rel="follow" title="Sponsor: Druckerei" href="http://www.allesdruck.de">Druckerei</a><!-- 201303011500 r.leo -->
cristy	4c54bbb	2011-03-17 13:53:13 +0000	[diff] [blame]	183	</div>
				184	<div class="sponsor">
cristy	575d5ee	2011-05-24 01:59:01 +0000	[diff] [blame]	185	<a rel="follow" title="Sponsor: Website Hosting" href="http://www.hostreviewgeeks.com">Website Hosting</a><!-- 201110010090 alexanian media -->
cristy	4bf6e23	2011-05-21 01:43:33 +0000	[diff] [blame]	186	</div>
				187	<div class="sponsor">
cristy	10549a1	2011-05-15 19:04:46 +0000	[diff] [blame]	188	<a rel="follow" title="Sponsor: Hotel München" href="http://www.messehotel-erb-muenchen.de">Hotel München</a><!-- 201111010450 cerb -->
cristy	af8d665	2011-02-04 21:57:45 +0000	[diff] [blame]	189	</div>
				190	<div class="sponsor">
cristy	10549a1	2011-05-15 19:04:46 +0000	[diff] [blame]	191	<a rel="follow" title="Sponsor: Best Web Hosting" href="http://webhostinggeeks.com">Best Web Hosting</a><!-- 201110010720 -->
cristy	7d52cd6	2010-10-01 17:26:59 +0000	[diff] [blame]	192	</div>
				193	<div class="sponsor">
cristy	10549a1	2011-05-15 19:04:46 +0000	[diff] [blame]	194	<a rel="follow" title="Sponsor: Flyer drucken" href="http://www.online-druck.biz">Flyer drucken</a><!-- 201109010900 Floeter-->
cristy	ee74264	2011-02-26 02:49:59 +0000	[diff] [blame]	195	</div>
				196	<div class="sponsor">
cristy	10549a1	2011-05-15 19:04:46 +0000	[diff] [blame]	197	<a rel="follow" title="Sponsor: Web Hosting Reviews" href="http://www.webhostingmasters.com">Web Hosting Reviews</a><!-- 201107011500 affliatelabel -->
cristy	851dbce	2010-08-06 21:40:00 +0000	[diff] [blame]	198	</div>
cristy	ec6b475	2011-01-08 03:16:23 +0000	[diff] [blame]	199	<div class="sponsor">
cristy	10549a1	2011-05-15 19:04:46 +0000	[diff] [blame]	200	<a rel="follow" title="Sponsor: Web Hosting Ratings" href="http://webhostingrating.com">Web Hosting Ratings</a><!-- 201110010720 -->
cristy	baacd17	2011-04-30 23:11:03 +0000	[diff] [blame]	201	</div>
				202	<div class="sponsor">
cristy	8413418	2011-06-15 22:59:00 +0000	[diff] [blame^]	203	<a rel="follow" title="Sponsor: Bildbearbeitung" href="http://www.bildschliff.de">Bildbearbeitung</a><!-- 2012060100300 strait.de-->
cristy	ec6b475	2011-01-08 03:16:23 +0000	[diff] [blame]	204	</div>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	205	</div>
				206	</div>
cristy	ce69bb0	2010-07-27 19:49:46 +0000	[diff] [blame]	207	</div>
cristy	3eaa0ef	2010-03-06 20:35:26 +0000	[diff] [blame]	208
cristy	ce69bb0	2010-07-27 19:49:46 +0000	[diff] [blame]	209	<div class="eastbar">
cristy	b52981c	2011-03-19 17:09:31 +0000	[diff] [blame]	210
cristy	3eaa0ef	2010-03-06 20:35:26 +0000	[diff] [blame]	211	</div>
				212
				213	<div class="main">
				214
cristy	2bd2a98	2011-02-15 00:52:58 +0000	[diff] [blame]	215	<h1>Enciphering and Deciphering Images</h1>
cristy	dcca3fa	2010-12-29 21:50:07 +0000	[diff] [blame]	216	<p class="navigation-index">[<a href="#encipher">Encipher an Image</a> • <a href="#decipher">Decipher an Image</a> • <a href="#caveats">Encipher and Decipher Caveats</a>]</p>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	217
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	218	<div class="doc-section">
				219
cristy	bebec40	2010-04-23 19:19:08 +0000	[diff] [blame]	220	<p>Most images, by design, are made to be viewed often and by many people. Web images, for example, may be viewed hundreds of times a day by a multitude of web vistors. However, in some cases, you may want to keep a particular image private so that only you or perhaps a select group of your friends or web visitors can view it. ImageMagick permits you to scramble your images such that unless someone knows your passphrase, they will be unable to view the original content.</p>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	221
				222	<p>You could use an <a href="http://www.wizards-toolkit.org/www/encipher.html">enciphering</a> utility to scramble your image but they typically scramble the entire file making it unrecognizable as an image format. With ImageMagick, only the pixels are scrambled. The scrambled image continues to be recognized as an image and will even display in your web page. However, the content appears as gibberish, nothing like the original content.</p>
				223
				224	</div>
				225
cristy	dcca3fa	2010-12-29 21:50:07 +0000	[diff] [blame]	226	<h2><a id="encipher"></a>Encipher an Image</h2>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	227	<div class="doc-section">
				228
cristy	bebec40	2010-04-23 19:19:08 +0000	[diff] [blame]	229	<p>Use the <a href="../www/command-line-options.html#encipher">-encipher</a> option to scramble your image so that it is unrecognizable. The option requires a filename that contains your passphrase. In this example we scramble an image and save it in the PNG format:</p>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	230
cristy	bebec40	2010-04-23 19:19:08 +0000	[diff] [blame]	231	<p class='crt'><span class="crtprompt"> $magick> </span><span class='crtin'>convert rose.jpg -encipher passphrase.txt rose.png</span></p>
				232	<p>Here we encipher an image using another image as the passphrase:</p>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	233
				234	<p class='crt'><span class="crtprompt"> $magick> </span><span class='crtin'>convert rose.jpg -encipher smiley.gif rose.png</span></p>
				235	</div>
				236
cristy	dcca3fa	2010-12-29 21:50:07 +0000	[diff] [blame]	237	<h2><a id="decipher"></a>Decipher an Image</h2>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	238	<div class="doc-section">
				239
cristy	bebec40	2010-04-23 19:19:08 +0000	[diff] [blame]	240	<p>Use the <a href="../www/command-line-options.html#decipher">-decipher</a> option to unscramble your image so that it is recognizable once again. The option requires a filename that contains your passphrase. In this example we unscramble an image and save it in the JPEG format:</p>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	241
cristy	bebec40	2010-04-23 19:19:08 +0000	[diff] [blame]	242	<p class='crt'><span class="crtprompt"> $magick> </span><span class='crtin'>convert rose.png -decipher passphrase.txt rose.jpg</span></p>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	243	</div>
				244
cristy	dcca3fa	2010-12-29 21:50:07 +0000	[diff] [blame]	245	<h2><a id="caveats"></a>Encipher and Decipher Caveats</h2>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	246	<div class="doc-section">
				247
cristy	d0bda5e	2010-09-21 16:22:45 +0000	[diff] [blame]	248	<p>Some formats do not support enciphered pixels-- the JPEG or GIF format, for
				249	example. To ensure your image format is supported, encipher a test image and
				250	verify you can restore its original content <em>before</em> you encipher any
				251	additional images in that format.</p>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	252
cristy	d0bda5e	2010-09-21 16:22:45 +0000	[diff] [blame]	253	<p>The image format also should be 8-bit and RGB (TrueColor). As such you may
				254	like to include the options "-depth 8 -type TrueColor" before the output
				255	filename. </p>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	256
cristy	d0bda5e	2010-09-21 16:22:45 +0000	[diff] [blame]	257	<p>The passphrase can be any combinations of letters and symbols. It should
				258	be a minimum of 12 character combinations to help ensure your image remains
				259	private. Also make sure your passphrase file permissions prevent others from
				260	reading it otherwise unintended users may be able to view the original image
				261	content.</p>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	262
cristy	d0bda5e	2010-09-21 16:22:45 +0000	[diff] [blame]	263	<p>You can only restore the original image content if you know your
				264	passphrase. If you lose or forget it, your original image content is lost
				265	forever.</p>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	266
cristy	d0bda5e	2010-09-21 16:22:45 +0000	[diff] [blame]	267	<p>ImageMagick only scrambles the image pixels. The image metadata remains
				268	untouched and readable by anyone with access to the image file.</p>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	269
cristy	d0bda5e	2010-09-21 16:22:45 +0000	[diff] [blame]	270	<p>ImageMagick uses the <a
				271	href="http://en.wikipedia.org/wiki/Advanced_Encryption_Standard">AES</a>
				272	cipher in cipher feedback mode. We use the passphrase to derive the cipher
				273	key and the required nonce.</p>
				274
				275	<p>Currently only ImageMagick can restore your enciphered image content. We
				276	use a standard cipher and mode so other vendors are encouraged to support
				277	enciphered image content.</p>
				278
				279	<p>Some small practical examples of image enciphering can be found in IM
cristy	2bd2a98	2011-02-15 00:52:58 +0000	[diff] [blame]	280	Examples <a href="http://www.imagemagick.org/Usage/transform/#encipher"
				281	>Encrypting Image Data</a>. </p>
cristy	3ed852e	2009-09-05 21:47:34 +0000	[diff] [blame]	282
cristy	bebec40	2010-04-23 19:19:08 +0000	[diff] [blame]	283	</div>
				284
cristy	3eaa0ef	2010-03-06 20:35:26 +0000	[diff] [blame]	285	</div>
				286
				287	<div id="linkbar">
cristy	ce69bb0	2010-07-27 19:49:46 +0000	[diff] [blame]	288	<span id="linkbar-west"> </span>
cristy	3eaa0ef	2010-03-06 20:35:26 +0000	[diff] [blame]	289	<span id="linkbar-center">
				290	<a href="http://www.imagemagick.org/discourse-server/">Discourse Server</a> •
cristy	a890294	2010-07-30 00:49:52 +0000	[diff] [blame]	291	<a href="http://www.imagemagick.org/MagickStudio/scripts/MagickStudio.cgi">Studio</a>
cristy	3eaa0ef	2010-03-06 20:35:26 +0000	[diff] [blame]	292	</span>
				293	<span id="linkbar-east"> </span>
				294	</div>
				295	<div class="footer">
cristy	7e41fe8	2010-12-04 23:12:08 +0000	[diff] [blame]	296	<span id="footer-west">© 1999-2011 ImageMagick Studio LLC</span>
cristy	3eaa0ef	2010-03-06 20:35:26 +0000	[diff] [blame]	297	<span id="footer-east"> <a href="http://www.imagemagick.org/script/contact.php">Contact the Wizards</a></span>
				298	</div>
				299	<div style="clear: both; margin: 0; width: 100%; "></div>
cristy	a890294	2010-07-30 00:49:52 +0000	[diff] [blame]	300	<script type="text/javascript">
				301	var _gaq = _gaq \|\| [];
				302	_gaq.push(['_setAccount', 'UA-17690367-1']);
				303	_gaq.push(['_trackPageview']);
				304
				305	(function() {
				306	var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true;
				307	ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js';
				308	var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s);
				309	})();
				310	</script>
cristy	3eaa0ef	2010-03-06 20:35:26 +0000	[diff] [blame]	311	</body>
				312	</html>