Review and Analysis of Multifarious Spatial Domain Steganography Techniques

Review and Analysis of Multifarious Spatial Domain Steganography Techniques

Dipalee Borse

Department of computer science Dr.D.Y. Patil ACS college, Pimpri – 411018

Shobhana Patil

Department of computer science Dr. D.Y. Patil ACS college, Pimpri – 411018

Abstract:-Steganography is fetching attraction because of rapid growth & use of internet as a communication medium. A steganography is a technique of invisible or secret communication. In steganography the secret message can be hidden into a cover_media which results in the stego_media, so that no one can realize its subsistence except the sender & receiver. There are various medium used as a cover such as image, audio, video, protocol, DNA etc. But image is mostly used as a cover media. There are several type and techniques of steganography, each having its own confines and rewards. In this paper we have explicated & analyzed the different spatial domain steganography techniques.

1. OVERVIEW OF STEGANOGRAPHY

   The word steganography chains the ancient greekwords steganos means "protected", and graphie means "writing". The first recorded use of the term was in 1499 by Johannes Trithemius. In ancient times, various entities were used as a cover for the secret message are invisible inks, wax tablets, shaved head of a trusted slave, etc. In digital steganography digital images, video, audio, DNA, Protocol, etc., are used as a cover media to hide the secret information Figure below shows the general process of steganography:

   Keywords: Steganography, Spatial domain, LSB, PVD, Steganalysis.

   SecretData

   Covermedia

   1. INTRODUCTION

      The use of internet as a communication media is increasing exponentially day by day.

      Information hiding techniques can be used to preclude the malicious modification, use or obliteration of the secret data. Information Security is process of keeping information secure, protecting its accessibility, integrity, and secrecy. There are several data hiding mechanisms like Steganography, Cryptography, and watermarking.

      Steganography is process of the hiding of a secret data within another media such as image, so that the presence of the hidden message is indiscernible. Steganalysis is reveals the secret data form stego media. Cryptography referred to as encryption, which is the process of converting ordinary

      Secret Key

      Embedding Algorithm

      Extraction Algorithm

      Extracted Secret Data

      Figure 1: Process of steganography

      Stego Media

      information (plaintext) into unintelligible text (cipher text). Decryption is a process of altering inarticulate cipher text back to plaintext.

      Watermarking is a hiding data in a carrier media like image. A Watermark may contain the copyright information to preserve the authenticity & integrity of information. Digital watermark remains constant even through recording, manipulation, compression & de compression, etc.; without affecting the quality of content.

      Steganography hide the subsistence of secret data so there is less chance of being cracked as compared to cryptography as in cryptography it encrypt the data and modify its structure which become suspicious to the attackers and they may apply decryption algorithms to access the secret data. Steganographys niche in security is to supplement cryptography, not replace it rather it can be better together.

      Steganography can be categorized as image steganography, audio steganography, video steganography etc.

      Image Steganographic Techniques

      Image steganography techniques can be divided into following domains.

      1. Substitution or Spatial Domain

      2. Transform Domain

      3. Statistical

      4. Distortion

      5. Cover Generation

      Spatial Domain Methods: Spatial steganography directly alter bits in the image pixel values in hiding data. Least significant bit (LSB) steganography is the simplest techniques to hides a secret message in the LSBs of pixel values very less perceptible misrepresentations. Changes in the value of the LSB are indiscernible for human eyes.

      Transform Domain Technique: Various transformations are used on the image to hide information in it. The process of embedding data in the frequency domain of a signal is sturdier than embedding principles that operate in the time domain. Most of the strong steganographic systems today operate within the transform domain Transform domain techniques is advantageous than spatial domain as they hide information in those areas of the image which are not affected in compression, cropping, or other image processing techniques. Transform domain techniques may outrun lossless and lossy format conversions

      Distortion Techniques: Decoder functions to check for differences between the original cover image and the distorted cover image in order to restore the secret message. The encoder adds a sequence of changes to the cover image. So, information is described as being stored by signal distortion. Using this technique, a stego object is created by applying a sequence of modifications to the cover image.

      Statistical Techniques: These are also called as model based technique be interpreted by humans. This technique is vulnerable to rotating, cropping, scaling attacks and also all the watermarking attacks.

      Cover Generation Techniques: In this technique, digital cover is generated only for the purpose of being a cover for secret communication .Regular expressions and mimic functions are used to generate a cover.

2. LITERATURE REVIEW

   1. R. Ibrahim and Teoh Suk Kuan. [1]

      The authors have proposed a new algorithm to hide the data Bitmap image. This algorithm used zipping technique. First the secret message is to be transferred into the text file, then convert that text file into zip file, Altering the zip file & secret key into binary codes. Encode binary codes using LSB replacement mechanism. It will generate better quality of stego_image as the image distortion cannot be seen by naked eyes. Also the secret message cannot be spotted easily by steganalysis. As BMP image is a bigger in size, So it can store large amount of data. Zip technique minimizes the total size of file & improves the security of file.

   2. S.K. Bandyopadhyay and I. K. Maitra[2]

      The authors have proposed alternative method for steganography using reference image for 4 bit images. The binary numbers of the data is stored in a 4 bit gray scale image and the occurrence and x; y coordinates are stored in the different data file. So for steganalysis both stego-image and data file must be available. With one of them one cannot determine the secret message. As a result this approach is more secure and time complexity of algorithm is simple and proportional to o(n).

   3. Amanpreet Kaur, Renu Dhir, and Geeta Sikka,[3]

      The scheme has proposed First component alteration technique. Each image have an array of pixels & each pixel is a combination of Red, Green, Blue values. In First component alteration technique the bits of first component (i.e. blue) of pixels of image can be substituted with bits of each character in secret data. As the visual perception of blue in R, G, B is low, and on changing it slightly will not

      affect the color intensity of image. So it reduces the picture distortion and it is unnoticeable by human eyes. Also gives increased PSNR than Pixel-Value Differencing (PVD) scheme, LSB3 etc. This scheme can integrate more secret data with improved image quality.

   4. V. K. Shrma and V Shrivastava[4]

      This proposed improved LSB substitution mechanism to hide image in image which minimizes the detection possibility. This approach is hiding the secret image into cover image using logic gates, which improves/increase PSNR of stego-image than First component alteration technique. This method can be used for 24 bit color & 8 bit gray scale image by adding conversion algorithm of color image into gray scale image. Also the numbers of steps are less which reduces the complexity of algorithm. The limitation of this algorithm is; as the number bits increases the PSNR values will be decreased i.e. the quality of stego-image will be reduced.

   5. Al-Shatnawi [5]

      The author has proposed a new method to hide secret message by finding the same or identical bits between cover image & secret message. Also set the locations of hidden data bits to a binary file which can be helpful at the time of retrieval of secret message. By this technique the maximum bits in image remain unchanged so the quality of image will never be degraded. It is different from [3], as here the author uses color image and [3] uses 4-bit binary images as a cover.

   6. Dr. T.Ch.Malleswara Rao, Koyi lakshmi prasad[6 This algorithm proposed an improved data hiding technique continuing the research in [5]. This algorithm does the searching of identical bits from cover image & the secret text. The 8 bit of secret character is divided into 3 segments such as (3bits; 3bit; 2 bits) so that the first 3bits can be matched & stored in 8 bits of Red, another 3 bits in green & remaining 2 bits in blue in a RGB pixel of cover image. & all non-identical bits can be stored in least significant bits of pixel. This algorithm is highly efficient

      and gives better resolution than existing models.

   7. Vikas Tyagi [7]

      This scheme has proposed a combination of cryptography and steganography technique to secure the secret data. First the secret information to be encrypted & then that data can be embedded into a cover image. This algorithm gives double layer of security as the original information cannot be extracted even after getting the data from stego-image which is actually an encrypted data. So it is secure & easy to implement practically

   8. Ankita Agarwal [8]

      This author has proposed a method with combination of cryptography & steganography. Before hiding a data it encrypted first using simplified data encryption standard(S- DES). After encryption that scrambled secret message is covered in an image by using alteration component technique. This technique provides two tier securities.

   9. Anil kumar, Rohini Sharma[9]

      Author has proposed an algorithm based on RSA algorithm & Hash-LSB algorithm. Author used RSA algorithm for

      encryption & Hash LSB method for hiding the encrypted data which is better than RSA-LSB technique. This algorithm gives better image quality gives high PSNR & MSE values because of less variation in image pixels and more security as encryption cannot be break without key as it is probably known to sender & receiver.

   10. Da-Chun Wu, Wen-Hsiang Tsai [10]

       Authors have proposed Pixel value differencing (PVD) method for embedding secret messages into a 256 gray- valued cover image. In PVD, the number of bits to be embedded in an image changes in consecutive pixel. It can store large amount of data, without losing properties of an image. PVD method is based on storing the information in the edges of an image as it cannot be noticed by naked eyes.Absolute Range of gray values (0, 255) is divided into smaller ranges and each range defined by lower and upper boundary. An absolute difference value is calculated from the values of the two pixels in each block. All possible difference values are classified into a number of ranges. Width of the range is calculated .The range near to 0 represents smooth area with small width and the ranges near to 255 represent contrast area with larger width.Embedding process take place in both pixels in the block which will generate new gray scale values for these pixels. Then, the difference value is replaced by a new value to embed the value of the secret message. This proposed scheme can hide more data with superior quality of stego -image.

       Butcolor pixel-components may exceed the range 0~255 in the stego image when applying PVD method.

   11. K. Mandal and Debashis[11]

       Authors have proposed a steganographic approach on color images, using PVD. They have removed drawback of [10] here. It will provide more security with better stego image quality than [10] method. First embed bits in 1st pixel block (two consecutive non-overlapping pixels) of the red component matrix, then in 1st block of green component matrix and lastly in blue, then again 2nd block of red matrix and so on. In the proposed method we have used the original PVD method to embed secret data. If pixel value surpasses the range, then check the bit-stream to be hidden. If MSB of the selected bit stream is 1 then we embeds one less number of bits, where MSB position is discarded from it; otherwise the bit number of hidden data depends on width of range. If the pixel value exceeds range again, then embed the value at one pixel, rather than both pixels of the pixel block, which will not exceed the range after embedding; where the other pixel is kept unchanged.

   12. Dinesh D. Patil & S. M. Bansode.[12]

       A novel stegnographic approach using four and eight pixel- value differencing is proposed.

       In the proposed system blocks of 2 (PVD), 4 and 8 pixels size are used to embed data in images. The data hiding procedure is independent in each block.

       The paper proposed modified approach termed as Block based PVD extends from 2-pixel block to 4 and 8-pixel block differencing where large amount of information can be embedded. It improves security of the data to be hidden with increasing embedding capacity. The proposed technique obtained better visibility with better PSNR ratio.

   13. Hsien-Wen Tseng1 and Hui-Shih Leng.[13]

       This proposed technique design a new quantization range table based on the perfect square number. For each pixel value choose the nearest perfect square number range as well as width of the range is defined. The width of the range is no longer a power of two, and if the difference value islocated in the first subrange, there is no modification needed.If we choose aproper width for each range and use the proposed methodwe can obtain better image quantity and higher capacity.The theoretical analysis shows the proposedscheme is well defined and has larger capacity and higherPSNR than [10].

3. COMPARATIVE STUDY:

   Terms used:

   Ref. No	PSNR	DHC	Security	Description
   [1]	High	High	High	Zipped data covered in BMP file
   [2]	High	Low	High	Use of reference file requires more size so increase in hidden data the size for 2 files in this algorithm also increases.
   [3]	High	High	Low	Change in blue pixel reduces image distortion
   [7]	Low	High	High	It is more secure as it uses encryption on secret data.
   [8]	Low	Mid	High	This algorithm is a combination of S-DES and LSB technique
   [9]	High	High	High	Author used RSA technique in combination with Hash-LSB method
   [10]	Low	Mid	low	Its a basic PVD. High secuity as compared to LSB
   [11]	Mid	high	Mid	It removed limitation of [10] So DHC is high than [10]
   [12]	High	High	High	In this PVD block of 4 & 8 pixels are used for RGB image

   PSNR: Peak signal to noise ratio DHC: Data hiding capacity

4. CONCLUSION

Information security is becoming a major issue nowadays. That is the reason steganography is fetching attraction of everyone to secure data while communicating. In above paper we have studied and analyzed different spatial domain steganographic methods which have been innovated from last few years. In spatial domain we focused on two major techniques are least significant bit and pixel value differencing technique. Every technique differs from every other technique. Few of them work on better image quality, while others aimed at data hiding capacity or provide more security. All these techniques can be vital for future research in steganography.

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