STEGANOGRAPHY

Steganography (a rough Greek translation of the term Steganography is secret writing) has been

used in various forms for 2500 years. Steganography is the art and science of hiding information

by embedding messages within other, seemingly harmless messages. It has found use in

variously in military, diplomatic, personal and intellectual property applications. Briefly stated,

steganography is the term applied to any number of processes that will hide a message within an

object, where the hidden message will not be apparent to an observer. This paper will explore

steganography from its earliest instances through potential future application.

INTRODUCTION

Johannes Trithemius (1462-1516) was a German Abbot. His writing, “Steganographia: hoe est

ars per occultam scripturam animi sui voluntatem absentibus aperiendi certa” is ostensibly a

work describing methods to communicate with spirits. A rough translation of the Latin title is:

“Steganography: the art through which writing is hidden requiring recovery by the minds of

men.” Although people have hidden secrets in plain sight—now called steganography—

throughout the ages, the recent growth in computational power and technology has propelled it to

the forefront of today’s security techniques.

What is Steganography: Steganography literally means

covered writing or hidden writing i.e., writing that is known

to casual observer, is derived from Greek words ‘steganos’

meaning covered or secret and ‘graphy’ meaning writing or

drawing. This technique includes all methods of secure and

secret communication that conceal the existence of secret

message. From the time of Herodotus in Greece till today, Steganography has been used in

various places. Today the field attains new dimensions with the advent of digital computer.

When a message is encrypted, it has no meaning, and it’s easy to understand that it contains

sensitive information, a secret – and someone might try to break it. Steganography solves this

problem by hiding the sensitive information in a harmless file called carrier file. Steganographic

software enables information to be hidden in graphics, sound files. By this technique data can be

hidden inside the normal picture without changing its appearance or size. The hidden messages

need not be encrypted and it can be in plain everyday English. Recent advances in computing

and recent interest in privacy has led to the development of steagnography.

SECRET COMMUNICATION METHODS:

The secret communications methods are invisible dots, microdots, character arrangement (other

than cryptographic methods of permutation and substitution), digital signatures, covert channels

and spread-spectrum signals.

It’s also notoriously known that there are different ways of hiding writing between the lines of an

ordinary letter. The text or picture that you drew would only appear if you colored over the

written area with a special marker. In this case a chemical reaction would take place once the

two substances touched thus revealing the hidden message.

The common form of invisible writing is through the use of invisible inks whose sources are

milk, vinegar, fruit juices and urine. These darken when heated and they are easy to decode.

With improvements in technology, many sophisticated inks were developed which react with

various chemicals. Some messages had to be ‘developed’ much as photographs are developed

with a number of chemicals in processing labs.

The Germans developed microdot technology during World War II which was referred to as ‘the

enemy’s masterpiece of espionage’. Microdots are photographs, the size of a printed period

having the clarity of standard-sized type-written pages. In the USSR all international mailings

were screened in attempt to detect any hostile activities.

IMPLEMENTATION OF STEGANOGRAPHY:

There are ways to hide information in an image, audio

and even text files. Moreover, if that message is in

addition encoded then it has one more supplemental level

of protection. Computer steganography is based on two

principles. The first one is that the files that contain

digitized images or sound can be altered to a certain extend without loosing their functionality

unlike other types of data that have to be exact in order to function properly, an example of that

would

be a

computer program.

If one step is missed or overlooked you cannot continue the process. The other principle deals

with the human inability to distinguish negligible changes in image color or sound quality, which

is especially easy to make use of in objects that contain redundant information, be it 16-bit

sound, 8-bit or even better 24-bit image. This just meaning that it is very hard to distinguish

minor changes in images with the human eye. Speaking of images, changing the value of the

least significant bit of the pixel color

Won’t result in any perceivable change of that color. One of the best and most widely spread

steganographic products for Windows95/98/NT is S-Tools.

Background, Evaluation method and Software evaluation which include S-Tools and Hide and

Seek v4.1 are the software packages which were reviewed with respect to Steganographic

manipulation of images. A very useful feature is the status line that displays the largest message

size that can be stored in the carrier file. All the softwares uses the LSB method to both images

and audio files. Steganography allows you to hide information in five innocent looking files

types: JPEG, PNG, BMP, HTML and WAV.

Allows the secure transfer

of passwords between two

computers using an

encrypted internet line.

An Application

Locker to password

protects any

application installed

on your computer.

Features five

innocent carriers for

hiding: JPEG, PNG,

BMP, HTML and

WAV.

Null ciphers (unencrypted messages) were also used. The real message is "camouflaged" in an

innocent sounding message. Due to the "sound" of many open coded messages, the suspect

communications were detected by mail filters. However "innocent" messages were allowed to

flow through. An example of a message containing such a null cipher is German Spy in World

War II:

“Apparently neutral's protest is thoroughly discounted

And ignored. Isman hard hit. Blockade issue affects

Pretext for embargo on by products, ejecting suets and

Vegetable oils. ”

Taking the second letter in each word the following message emerges:

Pershing sails from NY June 1.

TYPES OF STEGANOGRAPHY:

Steganography can be split into two types, these are Fragile and Robust. The following section

describes the definition of these two different types of steganography.

Fragile – Fragile steganography involves embedding information into a file which is destroyed if

the file is modified. This method is unsuitable for recording the copyright holder of the file since

it can be so easily removed, but is useful in situations where it is important to prove that the file

has not been tampered with, such as using a file as evidence in a court of law, since any

Codebook

tampering would have removed the watermark. Fragile steganography techniques tend to be

easier to implement than robust methods.

Robust – Robust marking aims to embed information into a file which cannot easily be

destroyed. Although no mark is truly indestructible, a system can be considered robust if the

amount of changes required to remove the mark would render the file useless. There are two

main types of robust marking: Fingerprinting and Water marking.

Text Techniques:

Hiding information is to conceal it in what seems to be inconspicuous text. It is more difficult

when it comes to electronic versions of text. Copies are identical and it is impossible to tell if it is

an original or a copied version. To embed information inside a document we can simply alter

some of its characteristics. These can be either the text formatting or characteristics of the

characters. The key to this problem is that we alter the document in a way that it is simply not

visible to the human eye yet it is possible to decode it by computer. Figure shows the general

principle in embedding hidden information inside a document.

Marked Documents

Again, there is an encoder and to decode it, there will be a decoder. The codebook is a set of

rules that tells the encoder which parts of the document it needs to change. It is also worth

pointing out that the marked documents can be either identical or different. By different, we

mean that the same watermark is marked on the document but different characteristics of each of

the documents are changed.

Image Techniques:

LSB – Least Significant Bit Hiding (Image Hiding) –This method is probably the easiest way of

hiding information in an image and yet it is surprisingly effective. It works by using the least

significant bits of each pixel in one image to hide the most significant bits of another.

(i) First load up both the host image and the image you need to hide.

(ii) Next chose the number of bits you wish to hide the secret image in. The more bits used in the

host image, the more it deteriorates. Increasing the number of bits used though obviously has a

beneficial reaction on the secret image increasing its clarity.

(iii) Now you have to create a new image by combining the pixels from both images. If you

decide for example, to use 4 bits to hide the secret image, there will be four bits left

for the host image.

Host Pixel: 10110001

Secret Pixel: 00111111

New Image Pixel: 10110011

(iv) To get the original image back you just need to know how many bits were used to store the

secret image. You then scan through the host image, pick out the least significant bits according

the number used and then use them to create a new image with one change - the bits extracted

now become the most significant bits.

Host Pixel: 10110011

Bits used: 4

New Image: 00110000

Audio Techniques

Spread Spectrum — spread spectrum systems encode data as a binary sequence which sounds

like noise but which can be recognised by a receiver with the correct key.

MIDI — MIDI files are good places to hide information due to the revival this format has had

with the surge of mobile phones, which play MIDI ring tones.

MP3 — The MP3 format is probably the most widespread compression format currently used for

music files. Due to this, it also happens to be very good for hiding information in. The more

inconspicuous the format, the more easily the hidden data may be overlooked.

Video — For video, a combination of sound and image techniques can be used. This is due to the

fact that video generally has separate inner files for the video (consisting of many images) and

the sound. So techniques can be applied in both areas to hide data. Due to the size of video files,

the scope for adding lots of data is much greater and therefore the chances of hidden data being

detected is quite low.

Limitations:

There are limitations on the use of steganography due to the size of the medium being used to

hide the data. In order for steganography to be useful the message should be hidden without any

major changes to the object it is being embedded in. This leaves limited room to embed a

message without noticeably changing the original object. This is most obvious in compressed

files where many of the obvious candidates for embedding data are lost. Detecting hidden data

remains an active area of research. How do you protect against malicious Steganography?

Unfortunately, all of the methods mentioned above can also be used to hide illicit, unauthorized

or unwanted activity. What can be done to prevent or detect issues with steganography? Other

uses for steganography range from the trivial to the abhorrent, including Criminal

communications, Fraud, Hacking, Electronic payments, Gambling, pornography, Harassment,

Intellectual property offensesViruses,Pedophilia.

Advantages:

Attempting to detect the use of steganography is called Steganalysis (the task of detecting and

possibly disabling steganographic information) and can be either passive, where the presence of

the hidden data is detected, or active, where an attempt is made to retrieve the hidden data it is

not infallible. But it considerably increases the work of any experienced code-breaker, who must

identify first the right carrier, extract the sensitive data from it, and only after that (if he gets this

far) – the hard work of breaking the code. Today, less painful but more cryptic methods could be

used to hide information in publicly available web site images. The image is visibly indiscernible

even to a trained eye. The only hope is to enlist science to see past the pixels, but is this possible?

STEGANOGRAPHY vs CRYPTOGRAPHY

Cryptography

(i) Message is not hidden.

(ii) Enemy can intercept the message.

(iii) Enemy can decrypt the message.

Steganography

(i) Message is hidden.

(ii) Enemy must discover the medium.

File encryption is based on encryption algorithms - a process capable of translating data into a

secret code. In Cryptography, encrypted message is sent. If it is intercepted, the interceptor

knows that the text is an encrypted message. In Steganography, the fact that the message is being

sent is unknown. So, the interceptor may not know the object contains a message. Steganography

is not intended to replace Cryptography but supplement it, Cryptography + Steganography =

Secured Steganography.

STEGANOGRAPHY vs DIGITAL WATERMARK

Digital watermark

Digital watermarks are employed in an attempt to provide proof of ownership and identify illicit

copying and distribution of multimedia information. The role of digital watermarking as a means

of aiding in copyright and ownership issues. Alternatives to digital watermarking techniques are

explored as countermeasures to distortion attacks against carrier. Despite, Steganography may

have nothing to do with the cover which is the object of communication.

MATLAB

OVERVIEW OF MATLAB

MATLAB is a high0performance language for technical computing. It integrates

computation, visualization, and programming in an easy-to-use environment where

problems and solutions are expressed in familiar mathematical notation.

Typical uses include

Math and computation

Algorithm development

Data acquisition

Modeling, simulation, and prototyping

Data analysis, exploration, and visualization

Scientific and engineering graphics

Application development, including graphical user interface building

MATLAB is an interactive system whose basic data element is an array that does not

require dimensioning. This allows you to solve many technical computing problems,

especially those with matrix and vector formulations, in a fraction of the time it would

take to write a program in a scalar non interactive language such as C or Fortran.

The name MATLAB stands for matrix laboratory. MATLAB was originally written to

provide easy access to matrix software developed by the LINPACK and EISPACK

projects. Today, MATLAB engines incorporate the LAPACK and BLAS libraries,

embedding the state of the art in software for matrix computation.

MATLAB has evolved over a period of years with input from many users. In university

environments, it is the standard instructional tool for introductory and advanced courses

in mathematics, engineering, and science.

In industry, MATLAB is the tool of choice for high-productivity research, development,

and analysis.MATLAB features a family of add-on application-specific solutions called

toolboxes. Very important to most users of MATLAB, toolboxes allow you to learn and

apply specialized technology. Toolboxes are comprehensive collections of MATLAB

functions (M-files) that extend the MATLAB environment to solve particular classes of

problems. Areas in which toolboxes are available include signal processing, control

systems, neural networks, fuzzy logic, wavelets, simulation, and many others.

The MATLAB System: The MATLAB system consists of these main parts:

Desktop Tools and Development Environment:

This is the set of tools and facilities that help you use MATLAB functions and files.

Many of these tools are graphical user interfaces. It includes the MATLAB desktop and

Command Window, a command history, an editor and debugger, a code analyzer and

other reports, and browsers for viewing help, the workspace, files, and the search path.

The MATLAB Mathematical Function Library:

This is a vast collection of computational algorithms ranging from elementary functions,

like sum, sine, cosine, and complex arithmetic, to more sophisticated functions like

matrix inverse, matrix eigenvalues, Bessel functions, and fast Fourier transforms.

The MATLAB Language: This is a high-level matrix/array language with control flow

statements, functions, data structures, input/output, and object-oriented programming

features. It allows both "programming in the small" to rapidly create quick and dirty

throw-away programs, and "'programming in the large" to create large and complex

application programs.

GRAPHICS:

MATLAB has extensive facilities for displaying vectors and matrices as graphs, as well

as annotating and printing these graphs. It includes high-level functions for two-

dimensional and three-dimensional data visualization, image processing, animation and

presentation graphics. It also includes low-level functions that allow you to fully

customize the appearance of graphics as well as to build complete graphical user

interfaces on your MATLAB applications.

MATLAB EXTERNAL INTERFACES:

This is a library that allows you to write C and Fortran programs that interact with

MATLAB. It includes facilities for calling routines from MATLAB (dynamic linking),

calling MATLAB as a computational engine, and for reading and writing MAT-files.

MATLAB DOCUMENTATION:

MATLAB provides extensive documentation, in both printable and HTML format, to

help you learn about and use all of its features. If you are a new user, start with this

Getting Started book. It covers all the primary MATLAB features at a high level,

including many examples.

To view the online documentation, select MATLAB Help from the Help menu in

MATLAB. Online help appears in the Help browser, providing task-oriented and

reference information about MATLAB features.

The MATLAB documentation is organized into these main topics:

· Desktop Tools and Development Environment - Startup and shutdown, the desktop, and

other tools that help you use MATLAB

Mathematics - Mathematical operations

Data Analysis - Data analysis, including data fitting, Fourier analysis, and time-

series tools

Programming - The MATLAB language and how to develop MATLAB

applications

Graphics - Tools and techniques for plotting, graph annotation, printing, and

programming with Handle Graphics®

3-D Visualization - Visualizing surface and volume data, transparency, and

viewing and lighting techniques

Creating Graphical User Interfaces - GUI-building tools and how to write

callback functions

External Interfaces - MEX-files, the MATLAB engine, and interfacing to Java,

COM, and the serial port

MATLAB also includes reference documentation for all MATLAB functions:

"Functions - By Category" - Lists all MATLAB functions grouped into categories

Handle Graphics Property Browser - Provides easy access to descriptions of

graphics object properties

C and Fortran API Reference - Covers those functions used by the MATLAB

external interfaces, providing information on syntax in the calling language,

description, arguments, return values, and examples

The MATLAB online documentation also includes

· Examples - An index of examples included in the documentation

· Release Notes - New features, compatibility considerations, and bug reports

· Printable Documentation - PDF versions of the documentation suitable for

printing.

In addition to the documentation, you can access demos from the Help browser by

clicking the Demos tab. Run demos to learn about key functionality of Math Works

products and tools.

Starting MATLAB

On Windows platforms, start MATLAB by double-clicking the MATLAB shortcut icon

on your Windows desktop.

On UNIX platforms, start MATLAB by typing matlab at the operating system prompt.

You can customize MATLAB startup. For example, you can change the directory in

which MATLAB starts or automatically execute MATLAB statements in a script file

named startup. m.

MATLAB Desktop:

When you start MATLAB, the MATLAB desktop appears, containing tools (graphical

user interfaces) for managing files, variables, and applications associated with MATLAB.

The following illustration shows the default desktop. You can customize the arrangement

of tools and documents to suit your needs.

IMAGE AND SOUND COMPRESSION USING

DISCRETE WAVELET TRANSFORM

SYNOPSIS

Signal analysts already have at their disposal an impressive arsenal of tools. Perhaps the most

well-known of these is Fourier analysis, which breaks down a signal into constituent sinusoids of

different frequencies. Another way to think of Fourier analysis is as a mathematical technique for

transforming our view of the signal from time-based to frequency-based. Fourier analysis has a

serious drawback. In transforming to the frequency domain, time information is lost. When

looking at a Fourier transform of a signal, it is impossible to tell when a particular event took

place.

If the signal properties do not change much over time — that is, if it is what is called a stationary

signal—this drawback isn’t very important. However, most interesting signals contain numerous

nonstationary or transitory characteristics: drift, trends, abrupt changes, and beginnings and ends

of events. These characteristics are often the most important part of the signal, and Fourier

analysis is not suited to detecting them.

In an effort to correct this deficiency, Dennis Gabor (1946) adapted the Fourier transform to

analyze only a small section of the signal at a time—a technique called windowing the signal.

Gabor’s adaptation, called the Short-Time Fourier Transform (STFT), maps a signal into a two-

dimensional function of time and frequency.

The STFT represents a sort of compromise between the time- and frequency-based views of a

signal. It provides some information about both when and at what frequencies a signal event

occurs. However, you can only obtain this information with limited precision, and that precision

is determined by the size of the window.

While the STFT compromise between time and frequency information can be useful, the

drawback is that once you choose a particular size for the time window, that window is the same

for all frequencies. Many signals require a more flexible approach—one where we can vary the

window size to determine more accurately either time or frequency.

Wavelet analysis represents the next logical step: a windowing technique with variable-sized

regions. Wavelet analysis allows the use of long time intervals where we want more precise low-

frequency information, and shorter regions where we want high-frequency information.

wavelet analysis does not use a time-frequency region, but rather a time-scale region. For more

information about the concept of scale and the link between scale and frequency, One major

advantage afforded by wavelets is the ability to perform local analysis — that is, to analyze a

localized area of a larger signal.

Wavelet analysis is capable of revealing aspects of data that other signal analysis techniques

miss, aspects like trends, breakdown points, discontinuities in higher derivatives, and self-

similarity. Furthermore, because it affords a different view of data than those presented by

traditional techniques, wavelet analysis can often compress or de-noise a signal without

appreciable degradation.

Image Compression

In this project we implement a lossy image/sound compressions technique where we used the

transform (wavelet) of the original signal, then calculated a threshold based on the compression

ratio required by the user. The image was compressed using the Matlab wavelet toolbox and

MatLab functions .

Applications:

Photography and printing

Face detection, feature detection, face identification

Satellite image processing

Medical image processing

-----###-----

Steganographic techniques

Physical steganography

Steganart example. Within this picture, the letter positions of a hidden

message are represented by increasing numbers (1 to 20), and a letter

value is given by its intersection position in the grid. For instance, the

first letter of the hidden message is at the intersection of 1 and 4. So,

after a few tries, the first letter of the message seems to be the 14th letter of the alphabet; the last

one (number 20) is the 5th letter of the alphabet.

Steganography has been widely used, including in recent historical times and the present day.

Possible permutations are endless and known examples include:

Hidden messages within wax tablets — in ancient Greece, people wrote messages on the

wood, then covered it with wax upon which an innocent covering message was written.

Hidden messages on messenger's body — also used 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 allegedly carried a warning to

Greece about Persian invasion plans. This method has obvious drawbacks, such as

delayed transmission while waiting for the slave's hair to grow, and the restrictions on the

number and size of messages that can be encoded on one person's scalp.

During World War II, the French Resistance sent some messages written on the backs of

couriers using invisible ink.

Hidden messages on paper written in secret inks, under other messages or on the blank

parts of other messages.

Digital steganography:

This article needs attention from an expert on the subject. See the talk page for details.

WikiProject History of Science or the History of Science Portal may be able to help recruit an

expert.

Image of a tree. Removing all but the two least significant bits of each color component produces

an almost completely black image. Making that image 85 times brighter produces the image

below.

Image of a cat extracted from above image.

Modern steganography entered the world in 1985 with the advent of the personal computer being

applied to classical steganography problems. Development following that was slow, but has

since taken off, going by the number of "stego" programs available: Over 800 digital

steganography applications have been identified by the Steganography Analysis and Research

Center. Digital steganography techniques include:

Concealing messages within the lowest bits of noisy images or sound files.

Concealing data within encrypted data or within random data. The data to be concealed is first

encrypted before being used to overwrite part of a much larger block of encrypted data or a block

of random data (an unbreakable cipher like the one-time pad generates ciphertexts that look

perfectly random if you don't have the private key).

Mimic functions convert one file to have the statistical profile of another. This can thwart

statistical methods that help brute-force attacks identify the right solution in a ciphertext-only

attack.

Concealed messages in tampered executable files, exploiting redundancy in the targeted

instruction set.Pictures embedded in video material (optionally played at slower or faster speed).

Injecting imperceptible delays to packets sent over the network from the keyboard. Delays in

keypresses in some applications (telnet or remote desktop software) can mean a delay in packets,

and the delays in the packets can be used to encode data.

Changing the order of elements in a set.

Content-Aware Steganography hides information in the semantics a human user assigns to a

datagram. These systems offer security against a non-human adversary/warden.

Blog-Steganography. Messages are fractionalized and the (encrypted) pieces are added as

comments of orphaned web-logs (or pin boards on social network platforms). In this case the

selection of blogs is the symmetric key that sender and recipient are using; the carrier of the

hidden message is the whole blogosphere.

Network steganography:All information hiding techniques that may be used to exchange

steganograms in telecommunication networks can be classified under the general term of

network steganography. This nomenclature was originally introduced by Krzysztof Szczypiorski

in 2003. Contrary to the typical steganographic methods which utilize digital media (images,

audio and video files) as a cover for hidden data, network steganography utilizes communication

protocols' control elements and their basic intrinsic functionality. As a result, such methods are

harder to detect and eliminate.

Typical network steganography methods involve modification of the properties of a single

network protocol. Such modification can be applied to the PDU (Protocol Data Unit), to the time

relations between the exchanged PDUs,or both (hybrid methods).Moreover, it is feasible to

utilize the relation between two or more different network protocols to enable secret

communication. These applications fall under the term inter-protocol steganography.

Network steganography covers a broad spectrum of techniques, which include, among others:

Steganophony - the concealment of messages in Voice-over-IP conversations, e.g. the

employment of delayed or corrupted packets that would normally be ignored by the receiver (this

method is called LACK - Lost Audio Packets Steganography), or, alternatively, hiding

information in unused header fields.

WLAN Steganography – the utilization of methods that may be exercised to transmit

steganograms in Wireless Local Area Networks. A practical example of WLAN Steganography

is the HICCUPS system (Hidden Communication System for Corrupted Networks)

Printed steganography

Digital steganography output may be in the form of printed documents. A message, the plaintext,

may be first encrypted by traditional means, producing a ciphertext. Then, an innocuous

covertext is modified in some way so as to contain the ciphertext, resulting in the stegotext. For

example, the letter size, spacing, typeface, or other characteristics of a covertext can be

manipulated to carry the hidden message. Only a recipient who knows the technique used can

recover the message and then decrypt it. Francis Bacon developed Bacon's cipher as such a

technique.

The ciphertext produced by most digital steganography methods, however, is not printable.

Traditional digital methods rely on perturbing noise in the channel file to hide the message, as

such, the channel file must be transmitted to the recipient with no additional noise from the

transmission. Printing introduces much noise in the ciphertext, generally rendering the message

unrecoverable. There are techniques that address this limitation, one notable example is ASCII

Art Steganography

Text steganography

Steganography can be applied to different types of media including text, audio, image and video

etc. However, text steganography is considered to be the most difficult kind of steganography

due to lack of redundancy in text as compared to image or audio but still has smaller memory

occupation and simpler communication. The method that could be used for text steganography is

data compression. Data compression encodes information in one representation into another

representation. The new representation of data is smaller in size. One of the possible schemes to

achieve data compression is Huffman coding. Huffman coding assigns smaller length codewords

to more frequently occurring source symbols and longer length codewords to less frequently

occurring source symbols.

Steganography using Sudoku Puzzle

This is the art of concealing data in an image using Sudoku which is used like a key to hide the

data within an image. Steganography using sudoku puzzles has as many keys as there are

possible solutions of a Sudoku puzzle, which is . This is equivalent to around 70

bits, making it much stronger than the DES method which uses a 56 bit key.

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 to be covertly communicated. The carrier is the signal, stream, or data

file into which the payload is hidden; which differs from the "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, stego file, or covert message.

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 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 might be referred to as a

candidate.

Countermeasures and detection

Detection of physical steganography requires careful physical examination, including the use of

magnification, developer chemicals and ultraviolet light. It is a time-consuming process with

obvious resource implications, even in countries where large numbers of people are employed to

spy on their fellow nationals. However, it is feasible to screen mail of certain suspected

individuals or institutions, such as prisons or prisoner-of-war (POW) camps. During World War

II, a technology used to ease monitoring of POW mail was specially treated paper that would

reveal invisible ink. An article in the June 24, 1948 issue of Paper Trade Journal by the

Technical Director of the United States Government Printing Office, Morris S. Kantrowitz,

describes in general terms the development of this paper, three prototypes of which were named

Sensicoat, Anilith, and Coatalith paper. These were for the manufacture of post cards and

stationery to be given to German prisoners of war in the US and Canada. If POWs tried to write a

hidden message the special paper would render it visible. At least two US patent were granted

related to this technology, one to Mr. Kantrowitz, No. 2,515,232, "Water-Detecting paper and

Water-Detecting Coating Composition Therefor", patented July 18, 1950, and an earlier one,

"Moisture-Sensitive Paper and the Manufacture Thereof", No. 2,445,586, patented July 20, 1948.

A similar strategy is to issue prisoners with writing paper ruled with a water-soluble ink that

"runs" when in contact with a water-based invisible ink.

In computing, detection of steganographically encoded packages is called steganalysis. The

simplest method to detect modified files, however, is to compare them to known originals. For

example, to detect information being moved through the graphics on a website, 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 extremely high compression rate makes steganography difficult, but not impossible. While

compression errors provide a hiding place for 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).

Steganographic techniques

Physical steganography

Steganart example. Within this picture, the letter positions of a hidden

message are represented by increasing numbers (1 to 20), and a letter

value is given by its intersection position in the grid. For instance, the

first letter of the hidden message is at the intersection of 1 and 4. So,

after a few tries, the first letter of the message seems to be the 14th

letter of the alphabet; the last one (number 20) is the 5th letter of the

alphabet.

Steganography has been widely used, including in recent historical times and the present day.

Possible permutations are endless and known examples include:

Hidden messages within wax tablets — in ancient Greece, people wrote messages on the

wood, then covered it with wax upon which an innocent covering message was written.

Hidden messages on messenger's body — also used 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 allegedly carried a warning to

Greece about Persian invasion plans. This method has obvious drawbacks, such as

delayed transmission while waiting for the slave's hair to grow, and the restrictions on the

number and size of messages that can be encoded on one person's scalp.

During World War II, the French Resistance sent some messages written on the backs of

couriers using invisible ink.

Hidden messages on paper written in secret inks, under other messages or on the blank

parts of other messages.

Digital steganography:

This article needs attention from an expert on the subject. See the talk page for details.

WikiProject History of Science or the History of Science Portal may be able to help recruit an

expert.

Image of a tree. Removing all but the two least significant bits of each color component produces

an almost completely black image. Making that image 85 times brighter produces the image

below.

Image of a cat extracted from above image.

Modern steganography entered the world in 1985 with the advent of the personal computer being

applied to classical steganography problems. Development following that was slow, but has

since taken off, going by the number of "stego" programs available: Over 800 digital

steganography applications have been identified by the Steganography Analysis and Research

Center. Digital steganography techniques include:

Concealing messages within the lowest bits of noisy images or sound files.

Concealing data within encrypted data or within random data. The data to be concealed is first

encrypted before being used to overwrite part of a much larger block of encrypted data or a block

of random data (an unbreakable cipher like the one-time pad generates ciphertexts that look

perfectly random if you don't have the private key).

Mimic functions convert one file to have the statistical profile of another. This can thwart

statistical methods that help brute-force attacks identify the right solution in a ciphertext-only

attack.

Concealed messages in tampered executable files, exploiting redundancy in the targeted

instruction set.Pictures embedded in video material (optionally played at slower or faster speed).

Injecting imperceptible delays to packets sent over the network from the keyboard. Delays in

keypresses in some applications (telnet or remote desktop software) can mean a delay in packets,

and the delays in the packets can be used to encode data.

Changing the order of elements in a set.

Content-Aware Steganography hides information in the semantics a human user assigns to a

datagram. These systems offer security against a non-human adversary/warden.

Blog-Steganography. Messages are fractionalized and the (encrypted) pieces are added as

comments of orphaned web-logs (or pin boards on social network platforms). In this case the

selection of blogs is the symmetric key that sender and recipient are using; the carrier of the

hidden message is the whole blogosphere.

Network steganography:All information hiding techniques that may be used to exchange

steganograms in telecommunication networks can be classified under the general term of

network steganography. This nomenclature was originally introduced by Krzysztof Szczypiorski

in 2003. Contrary to the typical steganographic methods which utilize digital media (images,

audio and video files) as a cover for hidden data, network steganography utilizes communication

protocols' control elements and their basic intrinsic functionality. As a result, such methods are

harder to detect and eliminate.

Typical network steganography methods involve modification of the properties of a single

network protocol. Such modification can be applied to the PDU (Protocol Data Unit), to the time

relations between the exchanged PDUs,or both (hybrid methods).Moreover, it is feasible to

utilize the relation between two or more different network protocols to enable secret

communication. These applications fall under the term inter-protocol steganography.

Network steganography covers a broad spectrum of techniques, which include, among others:

Steganophony - the concealment of messages in Voice-over-IP conversations, e.g. the

employment of delayed or corrupted packets that would normally be ignored by the receiver (this

method is called LACK - Lost Audio Packets Steganography), or, alternatively, hiding

information in unused header fields.

WLAN Steganography – the utilization of methods that may be exercised to transmit

steganograms in Wireless Local Area Networks. A practical example of WLAN Steganography

is the HICCUPS system (Hidden Communication System for Corrupted Networks)

Printed steganography

Digital steganography output may be in the form of printed documents. A message, the plaintext,

may be first encrypted by traditional means, producing a ciphertext. Then, an innocuous

covertext is modified in some way so as to contain the ciphertext, resulting in the stegotext. For

example, the letter size, spacing, typeface, or other characteristics of a covertext can be

manipulated to carry the hidden message. Only a recipient who knows the technique used can

recover the message and then decrypt it. Francis Bacon developed Bacon's cipher as such a

technique.

The ciphertext produced by most digital steganography methods, however, is not printable.

Traditional digital methods rely on perturbing noise in the channel file to hide the message, as

such, the channel file must be transmitted to the recipient with no additional noise from the

transmission. Printing introduces much noise in the ciphertext, generally rendering the message

unrecoverable. There are techniques that address this limitation, one notable example is ASCII

Art Steganography

Text steganography

Steganography can be applied to different types of media including text, audio, image and video

etc. However, text steganography is considered to be the most difficult kind of steganography

due to lack of redundancy in text as compared to image or audio but still has smaller memory

occupation and simpler communication. The method that could be used for text steganography is

data compression. Data compression encodes information in one representation into another

representation. The new representation of data is smaller in size. One of the possible schemes to

achieve data compression is Huffman coding. Huffman coding assigns smaller length codewords

to more frequently occurring source symbols and longer length codewords to less frequently

occurring source symbols.

Steganography using Sudoku Puzzle

This is the art of concealing data in an image using Sudoku which is used like a key to hide the

data within an image. Steganography using sudoku puzzles has as many keys as there are

possible solutions of a Sudoku puzzle, which is . This is equivalent to around 70

bits, making it much stronger than the DES method which uses a 56 bit key.

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 to be covertly communicated. The carrier is the signal, stream, or data

file into which the payload is hidden; which differs from the "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, stego file, or covert message.

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 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 might be referred to as a

candidate.

Countermeasures and detection

Detection of physical steganography requires careful physical examination, including the use of

magnification, developer chemicals and ultraviolet light. It is a time-consuming process with

obvious resource implications, even in countries where large numbers of people are employed to

spy on their fellow nationals. However, it is feasible to screen mail of certain suspected

individuals or institutions, such as prisons or prisoner-of-war (POW) camps. During World War

II, a technology used to ease monitoring of POW mail was specially treated paper that would

reveal invisible ink. An article in the June 24, 1948 issue of Paper Trade Journal by the

Technical Director of the United States Government Printing Office, Morris S. Kantrowitz,

describes in general terms the development of this paper, three prototypes of which were named

Sensicoat, Anilith, and Coatalith paper. These were for the manufacture of post cards and

stationery to be given to German prisoners of war in the US and Canada. If POWs tried to write a

hidden message the special paper would render it visible. At least two US patent were granted

related to this technology, one to Mr. Kantrowitz, No. 2,515,232, "Water-Detecting paper and

Water-Detecting Coating Composition Therefor", patented July 18, 1950, and an earlier one,

"Moisture-Sensitive Paper and the Manufacture Thereof", No. 2,445,586, patented July 20, 1948.

A similar strategy is to issue prisoners with writing paper ruled with a water-soluble ink that

"runs" when in contact with a water-based invisible ink.

In computing, detection of steganographically encoded packages is called steganalysis. The

simplest method to detect modified files, however, is to compare them to known originals. For

example, to detect information being moved through the graphics on a website, 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 extremely high compression rate makes steganography difficult, but not impossible. While

compression errors provide a hiding place for 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).

APPLICATIONS

Steganography is applicable to, but not limited to, the following areas.

1) Confidential communication and secret data storing

2) Protection of data alteration

3) Access control system for digital content distribution

4) Media Database systems

The area differs in what feature of the steganography is utilized in each system.

1. Confidential communication and secret data storing

The "secrecy" of the embedded data is essential in this area.

Historically, steganography have been approached in this area. Steganography provides us with:

(A) Potential capability to hide the existence of confidential data

(B) Hardness of detecting the hidden (i.e., embedded) data

(C) Strengthening of the secrecy of the encrypted data

In practice, when you use some steganography, you must first select a vessel data according to

the size of the embedding data. The vessel should be innocuous. Then, you embed the

confidential data by using an embedding program (which is one component of the steganography

software) together with some key. When extracting, you (or your party) use an extracting

program (another component) to recover the embedded data by the same key ( "common key" in

terms of cryptography). In this case you need a "key negotiation" before you start

communication.

Attaching a stego file to an e-mail message is the simplest example in this application area. But

you and your party must do a "sending-and-receiving" action that could be noticed by a third

party. So, e-mailing is not a completely secret communication method.

There is an easy method that has no key-negotiation. We have a model of "Anonymous Covert

Mailing System." See the reference.

There is some other communication method that uses the Internet Webpage. In this method you

don't need to send anything to your party, and no one can detect your communication.

Each secrecy based application needs an embedding process which leaves the smallest

embedding evidence. You may follow the following.

(A) Choose a large vessel, larger the better, compared with the embedding data.

(B) Discard the original vessel after embedding.

For example, in the case of Qtech Hide & View, it leaves some latent embedding evidence even

if the vessel has a very large embedding capacity. You are recommended to embed only 25% or

less (for PNG / BMP output) of the maximum capacity, or only 3% of the vessel size (for JPEG

output)..

2. Protection of data alteration

We take advantage of the fragility of the embedded data in this application area.

We asserted in the Home Page that "the embedded data can rather be fragile than be very

robust." Actually, embedded data are fragile in most steganography programs. Especially, Qtech

Hide & View program embeds data in an extremely fragile manner. We demonstrate this in the

other page.

However, this fragility opens a new direction toward an information-alteration protective system

such as a "Digital Certificate Document System." The most novel point among others is that "no

authentication bureau is needed." If it is implemented, people can send their "digital certificate

data" to any place in the world through Internet. No one can forge, alter, nor tamper such

certificate data. If forged, altered, or tampered, it is easily detected by the extraction program.

3. Access control system for digital content distribution

In this area embedded data is "hidden", but is "explained" to publicize the content.

Today, digital contents are getting more and more commonly distributed by Internet than ever

before. For example, music companies release new albums on their Webpage in a free or charged

manner. However, in this case, all the contents are equally distributed to the people who accessed

the page. So, an ordinary Web distribution scheme is not suited for a "case-by-case" and

"selective" distribution. Of course it is always possible to attach digital content to e-mail

messages and send to the customers. But it will takes a lot of cost in time and labor.

If you have some valuable content, which you think it is okay to provide others if they really

need it, and if it is possible to upload such content on the Web in some covert manner. And if

you can issue a special "access key" to extract the content selectively, you will be very happy

about it. A steganographic scheme can help realize a this type of system.

We have developed a prototype of an "Access Control System" for digital content distribution

through Internet. The following steps explain the scheme.

(1) A content owner classify his/her digital contents in a folder-by-folder manner, and embed the

whole folders in some large vessel according to a steganographic method using folder access

keys, and upload the embedded vessel (stego data) on his/her own Webpage.

(2)  On that Webpage the owner explains the contents in depth and publicize worldwide. The

contact information to the owner (post mail address, e-mail address, phone number, etc.) will be

posted there.

(3) The owner may receive an access-request from a customer who watched that Webpage. In

that case, the owner may (or may not) creates an access key and provide it to the customer (free

or charged)..

In this mechanism the most important point is, a "selective extraction" is possible or not.

4. Media Database systems

In this application area of steganography secrecy is not important, but unifying two types of data

into one is the most important.

Media data (photo picture, movie, music, etc.) have some association with other information. A

photo picture, for instance, may have the following.

(1) The title of the picture and some physical object information

(2) The date and the time when the picture was taken

(3) The camera and the photographer's information

Formerly, these are annotated beside the each picture in the album.

Recently, almost all cameras are digitalized. They are cheap in price, easy to use, quick to shoot.

They eventually made people feel reluctant to work on annotating each picture. Now, most home

PC's are stuck with the huge amount of photo files. In this situation it is very hard to find a

specific shot in the piles of pictures. A "photo album software" may help a little. You can sort the

pictures and put a couple of annotation words to each photo. When you want to find a specific

picture, you can make a search by keywords for the target picture. However, the annotation data

in such software are not unified with the target pictures. Each annotation only has a link to the

picture. Therefore, when you transfer the pictures to a different album software, all the

annotation data are lost.

This problem is technically referred to as "Metadata (e.g., annotation data) in a media database

system (a photo album software) are separated from the media data (photo data) in the database

managing system (DBMS)." This is a big problem.

Steganography can solve this problem because a steganography program unifies two types of

data into one by way of embedding operation. So, metadata can easily be transferred from one

system to another without hitch. Specifically, you can embed all your good/bad memory (of your

sight-seeing trip) in each snap shot of the digital photo. You can either send the embedded

picture to your friend to extract your memory on his/her PC, or you may keep it silent in your

own PC to enjoy extracting the memory ten years after. Qtech Hide & View v02may be a good

program for such purposes.

If  a "motion picture steganography system" has been developed in the near future, a keyword

based movie-scene retrieving system will be implemented. It will be a step to a "semantic movie

retrieval system."