Реферат на тему Steganography Essay Research Paper I INTRODUCTIONWhile Encryption

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Steganography Essay, Research Paper


While Encryption is detectable and a target for questions by the government

as well as hackers, Steganography takes it one step further and hides the

message within an encrypted message or other mediums; such as images, making it

virtually impossible to detect. It is a method related to the art of hiding a

secret message within a larger one in such a way that the unwanted person cannot

make out the presence or contents of the hidden message being sent. It can be

hidden in a picture or a sound file.

Most communication channels like telephone lines and radio broadcasts

transmit signals, which are always followed by some kind of, noise. This noise

can be replaced by a secret signal that has been changed into a form that is not

detectable from noise without knowledge of a secret key and this way, the secret

signal can be transmitted undetectable. [1]

A. Purpose of this paper

The purpose of this paper is to introduce steganography by explaining what it

is and how it works in conjunction with cryptography; provide a brief history;

note on the types of software programs available and how effective they are.

B. Body

First, I will define stenography, along with cryptography and digital

watermarking. I will also discuss the differences between the two. Second, I

will discuss briefly the history of steganography. Finally, I will review

several different software applications available that provide steganography,

how they are implemented and discuss any failures that may occur.

C. Conclusion

I will review the topics, which were discussed and give my personal opinion

on a particular software programs that I tried out.


A. Definition

Steganography comes from the Greek word Steganos meaning covered or secret,

basically hidden writing. Steganography is a non-cryptographic technique for

hiding data in the natural noise component of some other signal. Steganography

simply takes one piece of information and hides it within another. It uses

computer files (images, sounds recordings, even disks) which contain unused or

insignificant areas of data. Invisible inks, microdots, character arrangement,

digital signatures, covert channels, and spread spectrum communications also use

Steganography. Steganography takes advantage of these areas, replacing them with

information (encrypted mail, for instance). The least significant bits (LSBs) of

most digitized signals; music or images for instance; are randomly distributed.

You can change these bits to anything you like without noticeably changing the

music or images.

Cryptography disguises the text of the message but doesn?t hide the fact

that it is doing so. PGP (Pretty Good Privacy), a very strong cryptographic

tool. Its popularity doesn’t stem from the fact that nobody knows how to break

the system other than by a brute-force attack (which is a prerequisite for any

good cryptosystem). PGP became popular because it is extremely well designed,

fast, and has an excellent key management. There are many cryptographic

algorithms as strong as the one used in PGP, but PGP’s popularity and free

availability made it a de facto standard for secure electronic communications

all over the world. [2]

Digital watermarking which is a special technique of creating invisible

digital marks in images and audio files that carry copyright information. These

marks can be detected by special programs that can derive a lot of useful

information from the watermark: when the file was created, who holds the

copyright, how to contact the author etc. As you know tons of copyrighted

materials are reproduced, i.e. stolen on the Net every day so this technology

might be useful if you are a designer.

B. History

Steganography dates back to ancient Greece. During ancient Greek wars, if a

solder needed to notify his leader that he had information on enemies planning

to attack at a certain place and time, he would take a blank tablet write the

message then cover the tablet with wax. This was a way to conceal the

information as he passed through inspections. [3]

Another way they used to send hidden messages was to shave the messenger?s

head then tattoo the information. Once his hair had grown enough to cover the

message, he was then sent on his way to deliver the message. Of course, he had

to have his hair shaved again for the message to be revealed then let his hair

grow back.

During World War II, the Germans developed the microdot. A secret message was

photographically reduced to the size of a period, and affixed as the dot for the

letter ‘i’ or other punctuation on a paper containing a written message.

Microdots permitted the transmission of large amounts of printed data, including

technical drawings, and the fact of the transmission was effectively hidden.

Another form of hiding information was using Null ciphers (unencrypted

messages). The real message is "camouflaged" in an innocent sounding

message. Due to the "sound" of many open coded messages, mail filters

detected the suspect communications. However "innocent" messages were

allowed to flow through. An example of a message containing such a null cipher


News Eight Weather: Tonight increasing snow.

Unexpected precipitation smothers eastern towns. Be

extremely cautious and use snowtires especially heading

east. The highways are knowingly slippery. Highway

evacuation is suspected. Police report emergency

situations in downtown ending near Tuesday.

By taking the first letter in each word, the following message can be


Newt is upset because he thinks he is President.

The following message was actually sent by a German Spy in WWII [Kahn67]:

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.

Recently, Margaret Thatcher was so irritated with numerous press leaks of

cabinet documents, she had the word processors programmed to encode their

identity in the word spacing, so that disloyal ministers could be traced. [4]

C. Software

Three types of stegonagraphic software packages were evaluated by Neil

Johnson and Sushil Jajodia (authors of Exploring Steganography: Seeing the

Unseen) on their limitations and flexibility. [5] They are StegoDos, White Noise

Storm and S-Tools for Windows.

StegoDos is a share-ware program, which can be downloaded for free off the

internet (http://www.demcom.com). Its limitation is that it only works with 320

x 200-pixel images with 256 colors. Using a Renoir painting, they tried to

insert a photo of the Russian strategic bomber base (http://edcwww.cr.usgs.gov/dclass).

It could not be used because of size restrictions. They were able to use the

software in the Shakespeare image once it was cropped and fitted into the 320 x

200 pixel image. There was some distortion to the image but not very noticeable.

StegoDos uses LSBs (Least Significant Bits) to hide it?s messages. It is the

less successful tool of the three tested.

White Noise Storm is a DOS application and is very effective. It uses the LSB

approach and applies this to IBM Paintbrush (PCX) files. They were able to embed

the Russian strategic bomber base into the Renoir painting with no degradation

to the image. But, there were problems due to noise interference in the

integrity of the image, which altered the color palette considerably in the

Renoir painting. The main disadvantage of this encryption method is the loss of

many bits that can be used to hold information. [5]

The last software evaluated was S-Tools for Window. This freeware program

lets you hide files of any type in .gif and .bmp images as well as in .wav

sounds. Furthermore, S-Tools is actually a steganographic and cryptographic

product in one, because the file to be hidden is encrypted using one of the

symmetric key algorithms: Triple DES and IDEA are very secure as of today.

Another good steganography product is Steganos for Windows 95. It has almost

the same functions as S-Tools, but applies a different algorithm (HWY1) and is

able to hide data in .bmp and .wav files as well as in plain text and HTML files

in a very clever way. Steganos just adds a certain number of additional spaces

at the end of each text line. Steganos also adds an option of sending files from

your hard drive to the shredder, which makes it impossible to recover them.


In conclusion, I gave a brief definition of steganography as well as

cryptography and digital watermarking. Next, I went into a little history about

Steganography and where it originated. Finally, I discussed some of the software

that is available, what implementations were used and noted any limitations with

those software programs.

Steganography is much powerful tool when used in conjunction with

cryptography because it adds another layer of protection to an encrypted file.

Commercial applications of steganography, digital watermarking and digital

fingerprinting is now in use to track the copyright and ownership of electronic

media. [5]

[1] Markus Kuhn, 1995


[2] Introduction to PGP


[3] Mr. Byte, Steganography, 1997-1999


[4] Anderson, Ross J., Petitcolas, Fabien A.P., On The Limits of


16[4] 474-481, May 1998

[5] Johnson, Neil F., Steganography, 26-34


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