Tuesday, October 29, 2013

What are fractals?

Fractals have come up as an important question two times before the invention of computers. The first time was when British map makers discovered the problem with measuring the length of Britain's coast. On a zoomed out map, the coastline was measured to be 5,000 something or other. Sorry, I've forgotten the units. But anyway, by measuring the coast on more zoomed in maps, it got to be longer, like 8,000. And by looking at really detailed maps, the coastline was over double the original. You see, the coastline of Britain that's on a map of the world doesn't have all the bay's and harbors. A map of just Britain has more of these, but not all the little coves and sounds. The closer they looked, the more detailed and longer the coastline got. Little did they know that this is a property of fractals? (A finite area, aka Britain, being bounded by an infinite line)
The second instance of pre-computer fractals was noted by the French mathematician Gaston Julia. He wondered what a complex polynomial function would look like, such as the ones named after him (in the form of z^2 + c, where c is a complex constant with real and imaginary numbers). The idea behind the formula is that you take the x and y coordinates of a point, and plug them into z in the form of x + y*i, where i is the square root of negative one, square this number, and then add c, a constant. Then plug the resulting pair of real and imaginary numbers back into z, run the equation again, and keep doing that until the result is greater than some number. The number of times you have to run the equations to get out of its "orbit" can be assigned a color and then the pixel (x,y) gets turned that color, unless those coordinates can't get out of their orbit, in which case they're made black.
Later, Benoit Mandelbrot, an employee of IBM, thought about writing a program with a formula such as, oh... maybe Z*(n)^2 + c, and then running it on one of IBM's many computers. And they eventually got some pretty pictures. Mandelbrot was the first person to get computers do the many repetitive calculations to make a fractal look good. And now you know the mathematical aspects of fractals.
The basic concept of fractals is that they contain a large degree of self similarity. This means that they usually contain little copies of themselves buried deep within the original. And the also have infinite detail. Like the costal problem, the more you zoom in on a fractal, the more detail (coastline) you get. And this keeps going on forever and ever, so you could make a pretty movie of a fractal zooming in. Or two. So far I've made a Mandelbrot Zoom (1.1 meg) and a Julia Set Zoom (784 k). Both are AVI files, but I'm planning on converting them to streaming video or something.

Fractal Dimensions
One of the unique things about fractals is that they have non-integer dimensions. That is, while you are in the 3rd dimension, looking at this on a flat screen which can be considered more or less the 2nd dimension, fractals are in between the dimensions. Fractals can have a dimension of 1.8, or 4.12. Although fractals may not be in integer dimensions, they always have a smaller dimension than what they're on. If you make a fractal by drawing lines that obey a certain rule, like Koch's Curve, that fractal can't have a dimension higher than the paper it's drawn on, which would be 2 (it can be assumed that paper is as good as we're gonna get to 2 dimensional. Don't give me a hard time.)
And how exactly does one calculate how many dimensions a fractal has? Well, its tricky, which is why I took so long writing this page. First off, you must realize that in math, dimension means much more than whether it's a point, or if it's flat, or if it has length, width, and height. Dimension has been dummed up for the public so they could enjoy their 3D movies and the like. With this in mind, we can continue.
This can be simplified with logarithms. (Not an oxymoron) If, for instance, you take cube and multiply its edge length by 2, then you can fit 8 of the old cubes into the new cube. Taking these two numbers, you can find that log 8 / log 2 equals three. (I've cut out the math that leads to this simple equation). So, a cube has a dimension of 3, which we already knew. Eight is also 2 raised to the 3rd power. Not a coincidence.
It can be assumed that for any fractal object (of size P, made up of smaller units of size p), the number of units (N) that fits into the larger object is equal to the size ratio (P/p) raised to the power of d, which is called the Hausdorff dimension.-or-

Let's try this for Koch's Curve. Using only line segments that are 3 centimeters long (P), you make a simple Koch's Curve, which is just a Star of David. 12 segments, 3 centimeters per segment. If you take that to the next level and use line segments which are 1 centimeter long (p), you use 48 line segments. By cutting the length of the line segments by one third (P = 3, p = 1, P/p = 3), the number of line segments used (N) goes up four times (48 segments for p divided by 12 segments for P equals 4). That means N = 4, P/p = 3, so d = log 4 / log 3. Using a little help from a calculator, we find that Koch's Curve has a dimension of 1.2618595071429 Amazing but true.    

Uses of FractalsWhat good are mathematical pictures that aren't even whole dimensions? Well, they're pretty. As mentioned before, nature is full of fractal-like stuff. Twigs on trees look like the branches which they grow on, which look like the tree itself. Its the same thing with fern leaves, and so many other living things. Remember that artist who made paintings by splashing and dribbling paint onto a canvas? Even though it looks like a mess, his paintings, especially the later ones, look good. You can't place your finger on why, but I'd bet that you wouldn't mind one hanging up on your wall. The reason his paintings "look good" is that their fractal dimension is close to that of nature's, especially in the later paintings. So, when we see these paintings, they look natural, even if they're just spashes of paint.
Anyway, self-similarity is part of this world, so fractals can make pretty good copies of it. Artists have created very realistic looking landscapes composed of just a few fractal equations. Using just FractInt I've made not-so-bad looking mountains and even a moon, which looks more like one of the moons of Jupiter, but a moon none the less.

Fractals also have technological applications. Antennas have always been a tricky subject. Many antenna engineers have been reduced to using trial and error because of the complex nature of electromagnetism. The usual long, thin wire isn't the best way. Antenna arrays, another approach, consist of thousands of small antennas which are either placed randomly or regularly spaced. Fractals provide the perfect mix between randomness and order, and with fewer components. Parts of fractals have the disorder, while the fractal as a whole provides the order. By bending wires into the shape of Koch's Curve, more wire can be fit into less space, and the jagged shape also generates electrical capacitance and inductance. This eliminates the need for external components to tune the antenna or to broaden its range of frequencies. Motorola has started using fractal antennas in many of its cellular phones, and reports that they're 25% more efficient than the traditional piece of wire. They're also cheaper to manufacture, can operate on multiple bands, and can be put into the body of the phone. The journal Fractals showed why fractals work so well as antenna. For a antenna to work equally well at all frequencies, it must be symmetrical around a point and it must be self-similar, both of which fractals can provide.
Good Fractal Antennas
Serpinsky's Triangle
(11 KB)
Koch's Curve
(3 KB)
Serpinsky's carpet
(23 KB)
Check out my fractal zoom movies (avi)
Mandelbrot Zoom (1.1 Mg) Julia Set Zoom (784 Kb)

Clicking on each thumbnail will open the full sized picture in another window. All images were created with Fractint, and they're best viewed with more than 256 colors.
Coastline at Night
103 KB
46 KB
93 KB
31 KB
Koch's Curve

3 KB
Lamba Series
63 KB
50 KB
Mandelbrot Lightning
17 KB
Sub Mandelbrot
39 KB
49 KB
29 KB
61 KB
Serpinsky's Triangle
11 KB
Red Blue
13 KB
Serpinksy's carpet
23 KB
Fractal Mountain
Fractal Moon
Fractal Pictures

Fractal ResourcesI've used FractInt for all the fractals on this page. It's a really good program with lots of pre-programmed fractal types. It's also fast and has bells and whistles like color cycling, good palette editing, and 3d rendering.
Most of the stuff that I've learned about fractals has come from teachers, and it's hard to find good books about them, but The Mathematical Tourist has an interesting section on fractals. You can probably get it at any bookstore. It's very interesting.

Joomla - an overview

Joomla! is one of the most powerful Open Source Content Management Systems on the planet. It is used all over the world for everything from simple websites to complex corporate applications. Joomla! is easy to install, simple to manage, and reliable.
What is Joomla! ?

Joomla! is an award-winning Content Management System (CMS) that will help you build websites and other powerful online applications. Best of all, Joomla! is an open source solution that is freely available to everybody.

Joomla! in Action

Joomla! is used all over the world to power everything from simple, personal homepages to complex corporate web applications. Here are just some of the ways people use our software:
  • Corporate websites or portals
  • Online commerce
  • Small business websites
  • Non-profit and organizational websites
  • Government applications
  • Corporate intranets and extranets
  • School and church websites
  • Personal or family homepages
  • Community-based portals
  • Magazines and newspapers
  • the possibilities are limitless…
Joomla! can be used to easily manage every aspect of your website, from adding content and images to updating a product catalog or taking online reservations.

Joomla! for End Users

The basic Joomla! package is designed to be easy to install, even for non-programmers. Most people have no trouble getting our software up and running, and there is plenty of support available for newbies. We have a growing, active community of more than 40,000 friendly users and developers on our forums eager to help.
Once Joomla! is installed and running, it is simple for even non-technical users to add or edit content, update images, and to manage the critical data that makes your company or organization go. Anybody with basic word processing skills can easily learn to manage a Joomla! site.
Via a simple, browser-based interface you will be able to easily add new press releases or news items, manage staff pages, job listings, product images, and create an unlimited amount of sections or content pages on your site. You can try our simple demo to get quick taste of what Joomla! is all about.

Taking Joomla! to the Next Level

Out of the box, Joomla! does a great job of managing the content needed to make your website sing. But for many people, the true power of Joomla! lies in the application framework that makes it possible for thousands of developers around the world to create powerful add-ons and extensions. Here are just some examples of the hundreds of available extensions:
  • Dynamic form builders
  • Business or organizational directories
  • Document management
  • image and multimedia galleries
  • E-commerce and shopping cart engines
  • Forums and chat software
  • Calendars
  • Blogging software
  • Directory services
  • Email newsletters
  • Data collection and reporting tools
  • Banner advertising systems
  • Subscription services
  • and many, many more…
You can find more examples over at our growing Joomla! Extensions Directory. Prepare to be amazed at the amount of exciting work produced by our active developer community!

Joomla! for Developers

Many companies or organizations have requirements that go beyond what is available in the basic Joomla! package or in a freely available extension.
Thankfully, Joomla! offers a powerful application framework that makes it easy for developers to create sophisticated add-ons that extend the power of Joomla! into virtually unlimited directions.
Using the core framework, developers can easily build:
  • Integrated e-commerce systems
  • Inventory control systems
  • Data reporting tools
  • Custom product catalogs
  • Complex business directories
  • Reservation systems
  • Communication tools
  • Application bridges
  • or any kind of application to suit a unique need…
If your company or organization hires a third party Joomla! developer or builds in-house software using the Joomla! framework, you are building on an open platform that does not tie you to any one developer or to a proprietary, closed application.
You can learn more about developing on the Joomla! framework over at our developer’s network. The beauty of Joomla! is that you can leverage our framework and user interface to deliver applications to your end users in a familiar, powerful environment.

So what’s the catch?

There is no catch. Joomla! is free, open, and available to all under the GPL license. We don’t claim to be perfect, and can’t promise to meet every requirement in the world. But for many web applications, our software is perfectly suited for the job. We are adding great new features with each release, and with the help and advice of our incredible user community we plan on delivering award-winning software for years to come.

Please make a donation if you find our software useful and want to support the continued development of Joomla! Your donations help us by financially supporting developer conferences, presentation materials and travel expenses for things like the LinuxWorld Expo, as well as any other expenses that might come up as we develop and promote the award winning product we all love.

Why Open Source Matters?

You will see that our donations all go to an account at Open Source Matters (OSM). OSM is the legal entity we founded to provide legal protection and manage the assets of the project. In this case, OSM accepts all incoming donations, so we have only one legal entity to manage.

Donate Using PayPal

If you have a major credit card (Visa, MasterCard, American Express) or a PayPal account, donating is easy. Just click the image below to donate:

Donations from Outside of the United States

We welcome donations from anywhere in the world and in any currency. PayPal accepts a number of international currencies.

Donations by Other Methods

If you wish to donate to Joomla via direct bank deposit or mail a cheque or money order, please use the contact us on the Open Source Matters site for details.

Friday, 02 September 2005
We would like to thank those individuals and businesses that are actively supporting Joomla!
 Rochen Ltd.

Founded in early 2000, Rochen has focused on providing extremely reliable web hosting solutions for over half a decade. Rochen is not only the hosting partner for the official Joomla! website, but they were also nominated alongside Joomla! as a finalist in the category of "Best Linux/Open Source ISP/Internet Host" at the LinuxWorld Expo Awards held in London, UK in October 2005. As well as hosting thousands of websites powered by Joomla! Rochen also offer a complete range of web hosting services from shared and reseller hosting plans all the way up to fully managed dedicated servers and clusters.
Rochen and their team have been instrumental in getting the Open Source Matters (OSM) and Joomla! websites off the ground, providing us with the managed cluster of servers that we now use. To find out more about Rochen and the web hosting services they offer please visit: www.rochenhost.com.

Software Freedom Law Center (SFLC)

The Software Freedom Law Center provides legal representation and other law related services to protect and advance Free and Open Source Software. They have been instrumental in providing legal guidance as Joomla! advances to the next stage of this project.

VA Software - SourceForge

VA Software is at the center of the Open Source technology revolution through:
  • OSTG (Open Source Technology Group), the world's leading community-driven media network that includes such sites as Slashdot and Linux.com
  • SourceForge.net®, the world's largest Open Source development site
  • SourceForge® Enterprise Edition, enabling collaborative development in the enterprise

If you or your business is interested in sponsoring Joomla, please send an email to sponsors@opensourcematters.org

FAQ's - Whats in a Name?

1. What does Joomla mean?

The name Joomla is a phonetic spelling for the Swahili word "Jumla", which means "all together" or "as a whole". 

2. Why was it chosen?

It was chosen as the entire Core Team was unanimous in their commitment to protecting the interests of the project and community.

3. How was it chosen?

This name was chosen from thousands of recommendations by the community, and even went through an arduous review session by branding and marketing professionals who also felt that Joomla was the best choice of the lot.

1. Is Joomla! a fork of Mambo?

Some call it a fork. Some call it a spoon. Some call it an entire table setting. Whatever your philisophical persuasion, the facts are that Joomla is a continuation of the work of the Development Team which unanimously resigned from the Mambo project in August 2005.

2. Why start at Version 1.0?

We decided to reset the version number to 1.0 to reduce the confusion that could be created by having similar version numbers between Joomla! and Mambo. It is not necessarily a reflection on the fact that the project is immature, but rather that it is new and will be different from Mambo. Other projects, such as Firefox, have successfully delivered mature Version 1.0 products.

3. How do the versions compare?

Joomla version 1.0 is derived from Mambo but includes many additional bug fixes and security patches. Joomla version 1.5 is an extensive refactoring of the API as is Mambo version 4.6 to its codebase. Both applications continue maintain a similar user inferface (look and feel), similar default component and module sets. Both Joomla 1.5 and Mambo 4.6 will include internationisation support. Joomla will use an easy-to-use 'ini' format for their translation files while Mambo uses the 'gettext' format. Joomla 1.5 will correctly support the UTF-8 character set. Joomla 1.5 also includes many new features such as additional authentication models (LDAP, Gmail, etc), xml-rpc client-server support. It also natively supports database drivers for MySQL 4.1+ (on PHP 5) and has improved support for MySQL 5 as well as the groundings to support other database engines.

4. Are patches for Joomla! and Mambo interchangeable?

No. The two projects are maintained independently by different development teams.

5. Will Mambo addons continue to work in Joomla! ?

Addons (templates, components, modules, mambots and language packs) designed for Mambo 4.5.2 will generally run on Joomla 1.0. It is possible that some Mambo addons will run on Joomla 1.5. Mambo addons designed for version 4.6 will likely not run on Joomla, nor will extensions designed for Joomla 1.5 run on Mambo.

6. Can I just patch my existing Mambo site to make it Joomla! ?

No. The rebranding affects almost all files so it is not possible to patch just a few files.

7. Can I use my Mambo database for Joomla! ?

Yes. Joomla! 1.0 will be able to use a Mambo 4.5.2 database. It's likely that Joomla! 1.5 will be able to use a Mambo 4.6 database, with appropriate upgrading, but at this stage we cannot be certain.

8. What happens in the future when Joomla! and Mambo diverge?

That's a hard question to answer because we don't know. 

Steganography - An Overview

Steganography is the art and science of writing hidden messages in such a way that no one apart from the intended recipient knows of the existence of the message; this is in contrast to cryptography, where the existence of the message itself is not disguised, but the content is obscured.

The word "Steganography" is of Greek origin and means "covered, or hidden writing". Its ancient origins can be traced back to 440 BC. Herodotus mentions two examples of Steganography in The Histories of Herodotus. Demeratus sent a warning about a forthcoming attack to Greece by writing it on a wooden panel and covering it in wax. Wax tablets were in common use then as re-usable writing surface, sometimes used for shorthand. Another ancient example is that of Histiaeus, who shaved the head of his most trusted slave and tattooed a message on it. After his hair had grown the message was hidden. The purpose was to instigate a revolt against the Persians. Later, Johannes Trithemius's book Steganographia is a treatise on cryptography and steganography disguised as a book on black magic.

Generally, a steganographic message will appear to be something else: a picture, an article, a shopping list, or some other message - the covertext. Classically, it may be hidden by using invisible ink between the visible lines of innocuous documents, or even written onto clothing. During World War II a message was once written in morse code along two-colored knitting yarn. Another method is invisible ink underlining, or simply pin pricking of individual letters in a newspaper article, thus forming a message. It may even be a few words written under a postage stamp, the stamp then being the covertext.

The advantage of steganography over cryptography alone is that messages do not attract attention to themselves, to messengers, or to recipients. An unhidden coded message, no matter how unbreakable it is, will arouse suspicion and may in itself be incriminating, as in some countries encryption is illegal.
Steganography uses in electronic communication include steganographic coding inside of a transport layer, such as an MP3 file, or a protocol, such as UDP.
Steganographic messages are often first encrypted by some traditional means, and then a covertext is modified in some way to contain the encrypted message, resulting in stegotext. For example, the letter size, spacing, typeface, or other characteristics of a covertext can be manipulated to carry the hidden message; only the recipient (who must know the technique used) can recover the message and then decrypt it. Roger Bacon is known to have suggested such a technique to hide messages

Steganographic Techniques

Modern Steganographic Techniques

Concealing messages within the lowest bits of noisy images or sound files.
Concealing data within encrypted data. The data to be concealed is first encrypted before being used to overwrite part of a much larger block of encrypted data. This technique works most effectively where the decrypted version of data being overwritten has no special meaning or use. Examples of software that use this technique include FreeOTFE and TrueCrypt.
Chaffing and winnowing
Invisible ink
Null ciphers
Concealed messages in tampered executable files, exploiting redundancy in the i386 instruction set.
Embedded pictures in video material (optionally played at slower or faster speed).
A new steganographic technique involves injecting imperceptible delays to packets sent over the network from the keyboard. Delays in keypresses in some applications (telnet or remote desktop) can mean a delay in packets, and the delays in the packets can be used to encode data. There is no extra processor or network activity, so the steganographic technique is "invisible" to the user. This kind of steganography could be included in the firmware of keyboards, thus making it invisible to the system. The firmware could then be included in all keyboards, allowing someone to distribute a keylogger program to thousands without their knowledge.
Content-Aware Steganography hides information in the semantics a human user assigns a datagram; these systems offer security against a non-human adversary/warden.

Historical Steganographic Techniques

Steganography has been widely used in historical times, especially before cryptographic systems were developed. Examples of historical usage include:
Hidden messages in wax tablets: in ancient Greece, people wrote messages on the wood, then covered it with wax so that it looked like an ordinary, unused tablet.
Hidden messages on messenger's body: also in ancient Greece. Herodotus tells the story of a message tattooed on a slave's shaved head, hidden by the growth of his hair, and exposed by shaving his head again. The message, if the story is true, carried a warning to Greece about Persian invasion plans.
Hidden messages on paper written in secret inks under other messages or on the blank parts of other messages.
During and after World War II, espionage agents used microdots to send information back and forth. Since the dots were typically extremely small -- the size of a period produced by a typewriter (perhaps in a font with 10 or 12 characters per inch) or even smaller -- the stegotext was whatever the dot was hidden within. If a letter or an address, it was some alphabetic characters. If under a postage stamp, it was the presence of the stamp. The problem with the WWII microdots was that they needed to be written in a special ink, easily detected by holding a suspected paper up to a light and viewing it almost edge on. The microdot ink would shine when viewed from an extreme angle while the normal ink would not.
More obscurely, during World War II, a spy for the Japanese in New York City, Velvalee Dickinson, sent information to accommodation addresses in neutral South America. She was a dealer in dolls, and her letters discussed how many of this or that doll to ship. The stegotext in this case was the doll orders; the 'plaintext' being concealed was itself a codetext giving information about ship movements, etc. Her case became somewhat famous and she became known as the Doll Woman.
The one-time pad is a theoretically unbreakable cipher that produces ciphertexts indistinguishable from random texts: only those who have the private key can distinguish these ciphertexts from any other perfectly random texts. Thus, any perfectly random data can be used as a covertext for a theoretically unbreakable steganography. A modern example of OTP: in most cryptosystems, private symmetric session keys are supposed to be perfectly random (that is, generated by a good RNG), even very weak ones (for example, shorter than 128 bits). This means that users of weak crypto (in countries where strong crypto is forbidden) can safely hide OTP messages in their session keys.
An Example from Modern Practice

Image of a tree. By removing all but the last 2 bits of each color component, an almost completely black image results. Making the resulting image 85 times brighter results in the second image.

Image extracted from original image.
The larger the cover message is (in data content terms — number of bits) relative to the hidden message, the easier it is to hide the latter. For this reason, digital pictures (which contain large amounts of data) are used to hide messages on the Internet and on other communication media. It is not clear how commonly this is actually done. For example: a 24-bit bitmap will have 8 bits representing each of the three color values (red, green, and blue) at each pixel. If we consider just the blue there will be 28 different values of blue. The difference between say 11111111 and 11111110 in the value for blue intensity is likely to be undetectable by the human eye. Therefore, the least significant bit can be used (more or less undetectably) for something else other than color information. If we do it with the green and the red as well we can get one letter of ASCII text for every three pixels.
Stated somewhat more formally, the objective for making steganographic encoding difficult to detect is to ensure that the changes to the carrier (the original signal) due to the injection of the payload (the signal to covertly embed) are visually (and ideally, statistically) negligible; that is to say, the changes are indistinguishable from the noise floor of the carrier.
(From an information theoretical point of view, this means that the channel must have more capacity than the 'surface' signal requires, that is, there must be redundancy. For a digital image, this may be noise from the imaging element; for digital audio, it may be noise from recording techniques or amplification equipment. Any system with an analog (signal) amplification stage will also introduce so-called thermal or "1/f" noise, which can be exploited as a noise cover. In addition, lossy compression schemes (such as JPEG) always introduce some error into the decompressed data; it is possible to exploit this for steganographic use as well.)
Steganography can be used for digital watermarking, where a message (being simply an identifier) is hidden in an image so that its source can be tracked or verified.
In the era of Digital video recorder and devices like TiVo, TV commercials authors have figured out how to make use of such devices as well - by putting a hidden message which becomes visible when played at frame-by-frame speed (see KFC Unveils 'TiVo-proof' Ad).

Additional Terminology

In general, terminology analogous to (and consistent with) more conventional radio and communications technology is used; however, a brief description of some terms which show up in software specifically, and are easily confused, is appropriate. These are most relevant to digital steganographic systems.
The payload is the data it is desirable to transport (and, therefore, to hide). The carrier is the signal, stream, or data file into which the payload is hidden; contrast "channel" (typically used to refer to the type of input, such as "a JPEG image"). The resulting signal, stream, or data file which has the payload encoded into it is sometimes referred to as the package. The percentage of bytes, samples, or other signal elements which are modified to encode the payload is referred to as the encoding density and is typically expressed as a floating-point number between 0 and 1.
In a set of files, those files considered likely to contain a payload are called suspects. If the suspect was identified through some type of statistical analysis, it may be referred to as a candidate.

Rumored Usage in Terrorism

The rumors about terrorists using steganography started first in the daily newspaper USA Today on February 5, 2001.
The articles are still available online, and were titled "Terrorist instructions hidden online", and the same day, "Terror groups hide behind Web encryption". In July of the same year, the information looked even more precise: "Militants wire Web with links to jihad".
A citation from the USA Today article: "Lately, al-Qaeda operatives have been sending hundreds of encrypted messages that have been hidden in files on digital photographs on the auction site eBay.com". These rumors were cited many times - without ever showing any actual proof - by other media worldwide, especially after the terrorist attack of 9/11.
For example, the Italian newspaper Corriere della Sera reported that an Al Qaeda cell which had been captured at the Via Quaranta mosque in Milan had had pornographic images on their computers, and that these images had been used to hide secret messages (although no other Italian paper ever covered the story).
The USA Today articles were written by veteran foreign correspondent Jack Kelley, who in 2004 was fired after allegations emerged that he had fabricated stories and invented sources.
In October 2001, the New York Times published an article claiming that al-Qaeda had used steganographic techniques to encode messages into images, and then transported these via email and possibly via USENET to prepare and execute the September 11, 2001 Terrorist Attack.
Despite being dismissed by security experts, the story has been widely repeated and resurfaces frequently. It was noted that the story apparently originated with a press release from "iomart", a vendor of steganalysis software. No corroborating evidence has been produced by any other source.
Moreover, a captured al-Qaeda training manual makes no mention of this method of steganography. The chapter on communications in the al-Qaeda manual acknowledges the technical superiority of US security services, and generally advocates low-technology forms of covert communication.
The chapter on "codes and ciphers" places considerable emphasis on using invisible inks in traditional paper letters, plus simple ciphers such as simple substitution with nulls; computerized image steganography is not mentioned.
Nevertheless public efforts were mounted to detect the presence of steganographic information in images on the web (especially on eBay, which had been mentioned in the New York Times article).
To date these scans have examined millions of images without detecting any steganographic content (see "Detecting Steganographic Content on the Internet" under external links), other than test images used to test the system, and instructional images on web sites about steganography.

The detection of steganographically encoded packages is called steganalysis. The simplest method to detect modified files, however, is to compare them to the originals. To detect information being moved through the graphics on a website, for example, an analyst can maintain known-clean copies of these materials and compare them against the current contents of the site. The differences (assuming the carrier is the same) will compose the payload.
In general, using an extremely high compression rate makes steganography difficult, but not impossible; while compression errors provide a good place to hide data, high compression reduces the amount of data available to hide the payload in, raising the encoding density and facilitating easier detection (in the extreme case, even by casual observation).

Blood group checks out your traits!!

In a nutshell
Cannot stand people who hide the truth
Pessimistic and too sensitive
Cannot take orders easily
Romantic and sentimental
Basic Behavior
Make objectives clear
Careful about decision-making
Make decisions fast
Extremely practical
Possess great deal of confidence
Make things clear in black and white
Can be flexible
Excellent in analyses
Honest, optimistic and energetic
Care too much about social rules and standards
Do not care about rules
Give fair criticisms
Respect scientific and practical findings
Cannot decide when it comes to important issues
Strength and endurance depend on their aim
High tolerance for physical or repetitive work
Maintain the longest interest in what they do
Try to be hard-working
Give up easily if they find the job meaningless
Cannot take changes easily
Seem impatient
Tend to be impatient
Lose interest in a hobby easily
Dislike repetitious work

How do they see their future and past?
Positive about the past, thus do not regret about the past
Try hard to forget the past
Hard to forget recent affairs, but able to forget past and memories
Sentimental about the past
Seek financial stability for the future
Pessimistic about the future
More concern about the immediate problems than anything else
How do they express their emotions?
Usually stable and calm
Able to display cool outlook even though angry
Sensitive towards sincerity
Cool and objective
Usually cool and steady, but can get upset with an immediate, unsolved problem
Give frank, direct opinions
Take longer to heal a broken heart
Although joke a lot, could actually be very shy
Can get moody easily
Sensitive to others' opinions
Change moods like the weather

Cannot stop complaining when they are upset

How do they work?
Ability to concentrate vary from time to time, depending on aim
Creative and possess new ideas
Able to handle a wide scope of jobs
Mostly prefer to lead
Handle one thing at a time
Cannot differentiate between work and hobby
Value hard work
Can overlook details
Work a line between work and personal affairs
Cannot take orders
Quick in understanding
Highly responsible
Do not hesitate to introduce innovative changes and are not worried about theirs criticisms
Not highly responsible and unable to follow-up on a project until its completion
Tend to choose hobbies which help them release stress
Tend to be artistic in approach