Background of steganography

Background of steganographySteganography has been settled from Greek word Stego which means silver screen and Graphia which means writing. Steganography is an ancient technique of covert converse. The earliest salmagundi of Steganography has been reported by the Chinese. The inscrutable cognitive content was written in genuinely fine silk or constitution, and hence it was rolled into a b alone and cover with wax. The messenger would either swallow the ball or hide it in his nether parts. Herodotus has menti hotshotd in one of his seminal works of history, Histories during the 400B.C about the customs of privy writing. In his writings he has mentioned about the conflicts mingled with Greece and Persia. A king named Histiaeus encouraged the Aristagoras of Miletus to revolt against the Persian king. He apply to tonsure the head of his most trusted handmaidens and tattooed the scalps with cloak-and-dagger kernel and waited for the hair to grow. The servant employ to tra vel between the b posts without involveing allthing contentious freely. At the reception abolish his head would be tonsured again and the message will be conv shopping centerd. Similarly during the World War II, the Germans invented the use of microdots. Image restricting great exposit were scaled down to the size of microdots. The German usage of secret sharing is regarded as the recent evolution of Steganography. A nonher type of Steganography is during the Vietman War were the captured US armed force showed hand gestures during a photo sessions to convey some(prenominal) military secrets. The field of Steganography is limitless and what ever so kind of cover media advise be used for trickleing secret messages. Cover medias loafer be text, characterizations (grey, binary, color), audio, film etc. An example is illustrated as follows.Siva and Adam dined happily.The following message is not simply a plain text but it carries a secret message within it. By extracting ev ery second garner from each word we derive a secret message as follows.IndiaOther methods of non technical Steganography is employ lime and new(prenominal) citrus liquids to hold open secret information. The message will be imperceptible to the eye. When it is shown over a flame the writings will become perceptible. Steganography is method of information hiding. Steganography washbasin be considered as an art as well as perception for secret communication.The best way to explain the adjudicate of using Steganography is the prisoner Problem. today let us consider cardinal prisoners Alice and Bob, and Wendy to be the warden. Now if Alice and Bob want to devise a plan for escaping accordingly they got to drop dead with each other. If Wendy is a passive warden because he wont substitute in there communication but if he is an active warden then he will interfere and extract the secret message sent. therefrom Alice and Bob got to communicate in much(prenominal) a way that Wendy is not able to decipher there plan. This can be through by the technique of Steganography.Steganography is been used in golf-club to enable secret communication. It is too being used by terrorist for covert communication which is potential for endangering our field as well as world trade nurseion. Despite the ill movement there atomic number 18 positive sides of Steganography. For example a photographer can store the aperture size, future references etc while taking a picture. Steganography has a tolerant application in medical imaging were the details of the patients argon engraft within the medical moving picture. Similarly Steganography can be used for dissimilar friendly applications. It is also used for copy right protection using it along with Watermarking.The use of Steganography also has an important role in beef up national security. Steganography is defined as secret hiding. It can also be regarded as secret sharing since messages can be sh bed secretly without being hacked or corrupted.COMPARISON BETWEEN CRYPTOGRAPHY, STEGANOGRAPHY AND WATERMARKINGThe other forms of info hiding be cryptography and watermarking. cryptanalytics is a technique in which the secret message is encrypted and sent in an unin keyigent format. The basic dissimilarity between Steganography and cryptography is that Cryptography scrambles the data whereas Steganography just hides the data. Cryptography scrambles the secret data in such a way that it outs to be gibberish to any unintend drug exploiter. The secret data to be communicated is a mixture of replenishment and substitution and hence any unintended user shift come across the message.Steganography is different from Cryptography. Steganography rather hides the data whereas Cryptography encrypts the data. Steganography provides much more security when compared to cryptography because there is no chance of any unintended user to populate that a message is being sent whereas in Cryptography ther e will always be a suspicion that a message is being sent. therefore these are more prone to be hacked or suppressed.Watermarking is generally used for authentication and copyrights protection. Watermarking can be used for creating a reach in order that it is recognizable. It can also be used to mark a digital file so that it is intended to be visible (visible watermarking) or visible to its creator (invisible marking). The main purpose of watermarking is to pr regulart the illegal copying or claim of ownership of digital media.CHARACTERISTICS OF STEGANOGRAPHY, CRYPTOGRAPHY AND WATERMARKINGThe common characteristic between Steganography, Cryptography and Watermarking is that they transmit the secret information in such a way that only the receiver is able to decrypt the data. These techniques had been prevalent during the ancient times have been transported to the digital world. It has become nearly unfeasible to extract or detect the secret messages. In digital domain Steganogr aphy and watermarking have a tie and it is majorly used in digital images. These have other uses as well. Both cannot populate by themselves and hence they require cover objects. Steganography requires a cover media to carry the secret information and watermarking requires a carrier object which it is intended to protect. These similarities reach a link within them and hence some modifications can pass the transportation from one technique to another. Due the similarities range between these it is fractious to tag between the both but actually there is a remarkable difference between them. Cryptography encrypts data in two methods secure or unbreakable (e.g. One-time pad) strategys and breakable (e.g. RSA) systems. Through both the systems communication carried out is known to all. But it is time consuming and often unreal to crack a order. The robustness of the code lies upon the difficulties faced while reversing the code in different permutations and combinations. Due t o its robustness it is used for security purposes. For example Cryptography is used for online shopping, banking etc. The credit card number, expiration etc and other crucial informations are encrypted and sent so that an unintended user cant access the details.Steganography offers high carrier capacity keeping engraft message invisible and maintaining the fidelity of the cover media. The efficiency of the Steganographic method is that one shouldnt know that a media file has been altered in order for embedding. If the malicious user knows if there is some alteration the Steganographic method is defeated and less efficient. The engraft message is very fragile and hence if any modification is done to the stego image the whole secret message is corrupted. The effectiveness lies on the cogency to fool an unintended user. The layers of communication can be more than one layer. A secret message can be engraft with a digital image which in turn can be embed within another digital medi a or scene clippings.Watermarking is requisite in order for authentication and copyright protection of digital files. The embed watermarking is required in an object to make it impossible to remove completely. If the plant watermarking is removed, then the marked object is either distorted or destroyed do it useless for anyone. This is the reason why watermarking is more robust when compared to the other image processing techniques, such as compression, cropping, rotation etc. hence even if a fiddling bit of information is extracted by modification and temper the rightful owner can still claim ownership. If the owners name is embedded in the digital image and the particular image then the superior information is tampered and destroyed. Unlike Steganography, it is acceptable for everyone one to see the watermark embedded in it including the invisible ones.COMBINED EFFORTS OF STEGANOGRAPHY, CRYPTOGRAPHY AND WATERMARKINGCryptography is used as a paisano of the other two data hid ing techniques. Data is encrypted in both the techniques in order to increase the randomness of the Steganography to avoid the statistics-based attacks and to protect the hidden data in watermarking. Commonly it is a practice to first encrypt the data and then use any one of the embedded techniques.The importance of watermarking can be stated as follows. Suppose Rs hundred pen nib is introduced in December 2009 then watermarking is required in order to prevent illegal copies. If the bill is shown in light a clarified image will appear within the large image. The watermarking is actually a part of the large paper and is visible on both sides. so it becomes difficult to produce a paper with such features. In increment to these features some tiny writings which are invisible to the human eye are present in the paper.A banker having the necessary equipments (magnifying glass) can tell the difference between the original bill and the fake bill. Steganography makes its play here. Th e tiny printing done on the bill represents Steganography. It is implemented in order to achieve high security. The tiny printing done in the paper cannot be copied since any commercial printer is incapable to print such a fine and thin print leading to black spots. These are the reasons why Steganography is used for high security.Cryptography is actually implemented in the bill. A serial number is been printed in the bill which may contain information about the location and date of bill is printed or any other confidential information. The unique serial number for each bill can be used for tracking purposes. Using Steganography, Cryptography and Watermarking it becomes impossible to reproduce Rs100 bill. It must be kept in mind that all three are different and have different functionality.REQUIREMENTS OF STEGANOGRAPHYcAny digital media can be used as a cover media. The cover media can be a text, image (color, gray), audio or video etc. Cover media is required in order to hide and c arry the information. Usually digital images are required in order to hide secret messages. The secret message is hidden within the digital image. after(prenominal)ward the message is embedded within the cover mediaAn innocuous image consisting of scenery, stack and other objects are the nominees for cover media. The availability of natural images is not a problem due to the affordable price of digital cameras nowadays. Natural images are the best candidates for cover image since they have higher resolution providing flexibleness and other necessary need.Images are selected because the cover media is selected depending upon how the human visual system works. The gray image consists of pixels with intensity time value from 0 to 255. The human eye cannot differentiate between a pixel intensity of 244 and 245. It will appear both the pixel intensities to be same. Also natural image s contains lots of noise and hence there is lots of pixel value intensity difference especially in the edges. This variation in the pixel intensity is known as randomness and can be utilize to embed the data without providing any suspicion to human eye. The human visual system wont be able to distinguish between the image before modulation and the image after modulation. The secret data is embedded within the cover image. The resulting image is called a stego-image. The stego-image will appear to be the same as the original image. The human eye cannot usually distinguish between the stego-image and the original image except there is a probative change between the images. In that case the Steganographic method employed is ineffective. Hence there are certain Stego-system criteria which we have to follow while doing a Stegagraphic implementation. They are stated as follows.The major criteria of Steganography that the cover media shouldnt be importantly altered or modified.The embedded data should be directly encoded in the cover and not in the header or wrapper.The embedded data should be immune to modifications of the cover. That is if the cover media under goes any change then data embedded within it should be unaltered.During transmission there are chances of noise to occur and hence distortion due to noise cannot be eliminated. Due to this issue error coding algorithms should be included where ever it is required.It is advisable to avoid the suspicious portions while embedding the message in the cover. This because after embedding in these regions they become open to suspicion. For example by embedding in smooth portions of the image, the resultant image becomes distorted and open to suspicion. Hence such portions are often avoided and portions where there is variation in the pixel intensity are preferred.The embedding efficiency must be improved. Efficiency of the embedding capacity depends upon the number of pixels in the image used for embedding purposes.The stego-image should be robust to steganalysis. Steganalysis is a method of identifying the di fference between the original image and stego-image. Using steganalysis one can derive the information about the secret message.The stego-image should reassemble the original image and there should be any suspicion.The cover image should have high carrier capacity. That is the embedding capacity should be large. The amount of information present in the image should be resistant to distortion and should be comparable to the number of pixels present in the image.The three basic requirements of Steganography are robustness, capacity and imperceptibility. All these requirements should be satisfied for having an effective Steganographic method.