User:Grajan

Stegnography is defined as the art of hiding information, data or messages in an image. Even the different file formats can be used for the purpose of hiding the information like for example the video or audio etc. The purpose is to pass on the information with out any regard or knowledge of others safely to the destination. The advantage of stegnography is that those who are outside the party even do not realize that some sort of communication is being done.

This is an alternative method used instead of encryption. In case of the images the bits are used and the contrast size of the image matters a lot. If the computer criminal has used some sort of stegnography then it is required for the computer forensics professional to decode that information to acquire valid evidence that can be produced in the court of law. The advantage of unused bits within the structure of a file or those bits those are mostly not detectable if altered are used. If not identified as a steganographic message; there is no chance of any leakage of information.

This practice of embedding secret messages in other messages in a way that prevents an observer from learning that anything unusual is taking place. Encryption, by contrast, relies on ciphers or codes to scramble a message.

The message rides safely and secretly to its destination. The message can be decrypted only if it is identified. So it has an advantage over the encryption process. In case of the encrypted text; however complicated may be the cipher applied but at least the encrypted message is detectable as an encrypted message.

In general a stegnographic message can appear in many different formats. Only the person or the destination will be able to understand the hidden meaning. It appears as something else like for example an article, shopping list, a picture, or some other cover message.

If the message is much larger then data content terms are also even more. The content terms here relate to the number of bits used. They are relative to the hidden messages. More number of bits will result in much ease to hide. Hence the digital pictures and images are used for the purpose of stegnography. Usually the images with large amount of data are used for the purpose.

They can be easily stored in the computer or any other storage media. A computer forensics even if encounters the data is also not even able to realize the evidence. These stegnographic images can be easily used over the internet to pass the messages for communication. The principle of stegnography is basically from olden days.

While we are discussing it in terms of computer security, steganography is really nothing new, as it has been around since the times of ancient Rome. For example, in ancient Rome and Greece, text was traditionally written on wax that was poured on top of stone tablets. If the sender of the information wanted to obscure the message - for purposes of military intelligence, for instance - they would use steganography: the wax would be scraped off and the message would be inscribed or written directly on the tablet, wax would then be poured on top of the message, thereby obscuring not just its meaning but its very existence.

Let us consider an example that can be used to describe how the task of stegnography is actually achieved. For example a 24 bit bitmap image will have 8 bits representing the color values. Each of the three color values that is the red, green, and blue have a relative value at each pixel.

The difference between say 1111111111 and 1111111110 in the value for blue intensity is unlikely to be detected by a human eye. Hence, it is possible to represent the least significant bit for something else rather than color information bit. It is possible to get one letter in an ASCII character set if we do it with the other colors such as green and the red as well. So for each of the three pixels it is possible to have one letter of ASCII text. Winnowing and Chaffing are the recent techniques in stegnography. Also Null ciphers can be used.

Steganography (also known as "steg" or "stego") is "the art of writing in cipher, or in characters, which are not intelligible except to persons who have the key; cryptography". In computer terms, steganography has evolved into the practice of hiding a message within a larger one in such a way that others cannot discern the presence or contents of the hidden message. In contemporary terms, steganography has evolved into a digital strategy of hiding a file in some form of multimedia, such as an image, an audio file (like a .wav or mp3) or even a video file.

In the 19th century, Thomas Jefferson proposed a new ciphering machine. It was a cylinder of discs mounted on a spindle. On the edge of each disc were the letters of the alphabet, arranged in random sequence. A cryptographer could align the discs to spell out a short message across the cylinder. He would then look at another row across the cylinder, which would appear to be gibberish, and send that to the recipient. The recipient would use an identical cylinder to spell out the series of nonsense letters, then scan the rest of the cylinder, looking for a message spelled out in English. In 1922, the United States Army adopted a device very similar to Jefferson's; other branches of the military soon followed suit [source: Kahn].

Perhaps the most famous ciphering device was Germany's Enigma Machine from the early 20th century. The Enigma Machine resembled a typewriter, but instead of letter keys it had a series of lights with a letter stamped on each. Pressing a key caused an electric current to run through a complex system of wires and gears, resulting in a ciphered letter illuminating. For instance, you might press the key for the letter "A" and see "T" light up

What made the Enigma Machine such a formidable ciphering device was that once you pressed a letter, a rotor in the machine would turn, changing the electrode contact points inside the machine. This means if you pressed "A" a second time, a different letter would light up instead of "T." Each time you typed a letter, the rotor turned, and after a certain number of letters, a second rotor engaged, then a third. The machine allowed the operator to switch how letters fed into the machine, so that when you pressed one letter, the machine would interpret it as if you had pressed a different letter.

What is the use of Steganography?

Like many security tools, steganography can be used for a various reasons, some good, some not so good. Legitimate purposes can include things like watermarking images for reasons such as copyright protection. Digital watermarks (also known as fingerprinting, significant especially in copyrighting material) are similar to steganography in that they are overlaid in files, which appear to be part of the original file and are thus not easily detectable by the average person. Steganography can also be used as a way to make a substitute for a one-way hash value (where you take a variable length input and create a static length output string to verify that no changes have been made to the original variable length input)[4]. Further, steganography can be used to tag notes to online images (like post-it notes attached to paper files). Finally, steganography can be used to maintain the confidentiality of valuable information, to protect the data from possible sabotage, theft, or unauthorized viewing[5].

Unfortunately, steganography can also be used for illegitimate reasons. For example, if someone was trying to steal data, they could conceal it in another file or files and send it out in an innocent looking email or file transfer. Furthermore, a person with a hobby of saving pornography, or worse, to their hard drive, may choose to hide the evidence through the use of steganography. And, as was pointed out in the concern for terroristic purposes, it can be used as a means of covert communication. Of course, this can be both a legitimate and an illegitimate application.

Perhaps the strangest example of steganography is a program called Spam Mimic, based on a set of rules, called a mimic engine, by Disappearing Cryptography author Peter Wayner. It encodes your message into what looks just like your typical, quickly deleted spam message.

Steganography is a fascinating and effective method of hiding data that has been used throughout history. Methods that can be employed to uncover such devious tactics, but the first step are awareness that such methods even exist. There are many good reasons as well to use this type of data hiding, including watermarking or a more secure central storage method for such things as passwords, or key processes. Regardless, the technology is easy to use and difficult to detect. The more that you know about its features and functionality, the more ahead you will be in the game.