Study On Steganography Techniques

Abstract—The quick development in correspondence advancesand the expanded accessibility of people in general systems(Internet) encouraged information exchange. Anyway the gen-eral population correspondence channels are defenseless againstsecurity assaults that may prompt unapproved access to somedata. Encryption has been utilized to continue and keep theseassaults. In any case, when the data is unscrambled it will bepresented to the assailants again and it won’t have any securityinsurance. Steganography is the investigation of implanting themystery messages inside other medium documents (content,sound, picture, and video) in a way that shrouds the presenceof the mystery message by any means. Steganography appliesan implanting procedure in which the repetitive bits of themedium are supplanted by the bits of the mystery message. Steganography is the field of steganography in which the mediumthat used to convey the mystery information is a computerizedpicture. Picture Steganography is a vital zone of research in theongoing years. This article surveys the steganography in lightof advanced pictures; representation of the idea and the regularmethodologies are examined.

Introduction

Nowadays internet offers more convenience in transmittinglarge amounts of information in many parts of theworld. However,the safety and security of long distancecommunication remains a problem. In order to solve thisproblem by using steganography schemes. The process ofhiding secret data in the cover image while hiding its ownexistence is referred to as steganography. Audio, video, text,images etc can be the secret data. The confidential data isconverted into binary form and then it is embedded into thecover image This output image is called as stegoimage. Ifthe cover image is an image file, then the technology iscalled as image steganography. Securing multimedia dataneeds blocking unauthorized people from access, distortion,destruction, detection or change of data during its trasfer. There are two basic methods for data security that isencryption and steganography.

The encryption methodprotects data by converting it to an unclear form that cannotbe understand by hackers. A data hiding system consists oftwo main processes;the embedding process,which embeds thesecret file inside the stego file, and the extracting processwhich retrieves the embedded secret file. Some data hidingschemes use lossy compression, to allow for higher hidingcapacity at the expense of loosing bits of the secret file. Imagesteganography indicates sending the secret data in the coverimage while hiding the very existence of it self. Before embed-ding the secret data in the cover image, it is encrypted in orderto obtain betterlevel of security. Steganalysis is concernedwith eld of defeating steganographic techniques

A. Steganography

Image Steganography requires following elements to carryout the work:

• Covermedium: It is an image that holds secret message.
• Secretmessage: it is message to be transmitted. It can beplain or encrypted text, images or any other data.
• Stego-key: it is key used to hide the message (May ormay not be used). The well- known technique namelyLSB embedding process. In order to hide information in the cover image, someSteganographic techniques have gaineda great importance in a certain number of applicationareas. Steganography is sometimes used when encryptionis prohibited. Or, more commonly, steganography isused to supplement encryption. By using steganography,an encrypted le can still hide information, even if theencrypted le is decrypted; the hidden message may notbe visible. Several approaches have been proposed to hideinformation. LSB is mainly based on the modication ofthe least signicant bit of each pixel in the image.

B. Factors Affecting a Steganographic Method

The effectiveness of any steganographic method canbe determined by comparing stego-image with thecover Image. There are some factors that determines theefciency of a technique.

These factors are:

1. Robustness: Robustness refers to the ability ofembedded data to remain intact if the stego- imageundergoes transformations, such as linear and non-linearltering,sharpening or blurring, addition of random noise,rotations and scaling, cropping or decimation, lossycompression.
2. Imperceptibility: The imperceptibility meansinvisibility of a steganographic algorithm. Becauseit is the rst and foremost requirement, since the strengthof steganography lies in its ability to be unnoticed bythe human eye.
3. Payload Capacity: It refers to the amount of secretinformation that can be hidden in the cover source. Watermarking usually embed only a small amount ofcopyright information, whereas, steganography focusat hidden communication and therefore have sufcientembedding capacity.
4. PSNR(Peak Signal to Noise Ratio): It is dened as theratio between the maximum possible power of a signaland the power of corrupting noise that affects the delityof its representation. This ratio measures the qualitybetween the original and a compressed image. The highervalue of PSNR represents the better quality of thecompressed image.
5. MSE (Mean Square Error): It is dened as the averagesquared difference between a reference image and adistorted image. The smaller the MSE, the more efcientthe image steganography technique. MSE iscomputedpixel-by-pixel by adding up the squared differences ofall the pixels and dividing by the total pixel count.
6. SNR (Signal to Noise Ratio): It is the ratio betweenthe signal power and the noise power. It compares thelevel of a desired signal to the level of background noise.

Conclusion

In this paper different steganographic techniques were stud-ied. Each of these techniques tries to satisfy the three mostimportant factors of steganographic design. They are impercep-tibility, capacity, and robustness. Multimedia files are usuallylarger than text and still image documents, hence requirehigher embedding space within cover files. Least SignificantBit Substitution(LSB)is the most commonly used stenographictechnique. The least significant bit (LSB) technique is a suit-able choice for high capacity hiding. There have been severalalternatives of the LSB method regarding the number of leastsignificant bits per pixel or element of a pixel that can bereplaced,such as 1-bit,2-bit,3-bit,and 4-bit LSB. As many newapplication areas are identified like internet banking, mobilecommunication security,cloud security etc. , the insight into thesteganographic principles will definitely guide us to identifynew areas and to improve its applications in the alreadyexisting application areas also.