A Novel Implementation of Color Image Steganography Using PVD Subhan Bhasha Shaik #, V V N Sujit *2 M.Tech. Student, 2 Assistant Professor,,2 Department of ECE, Sasi Institute of Technology and Engineering. bhasha@sasi.ac.in 2 vvnsujit@sasi.ac.in Abstract Steganography is the art of science and technology of hiding data in images in such a way that only sender and receiver knows the process of hiding and extraction. In this paper, data is placed in color images which have three components named as Red, Green and Blue and each component intensity is represented by eight bits. In our paper, Pixel value difference (PVD) is applied on color images by making Red and Green components as one group and Green and blue components as one group. This method gives good information capacity when compared with other methods and the algorithm is tested on different images using MATLAB 203A Keywords- Pixel value Differencing, Steganography, embedding, extraction I. INTRODUCTION The idea of communicating secretly is as old as communication itself. Early steganography was messy. Before phones, before mail, before horses, messages were sent on foot. If you wanted to hide a message, you had two choices: have the messenger memorize it, or hide it on the messenger. While information hiding techniques have received a tremendous attention recently, its application goes back to Greek times. According to Greek historian Herodotus, the famous Greek tyrant Histiaeus, while in prison, used unusual method to send message to his son-in-law. He shaved the head of a slave to tattoo a message on his scalp. Histiaeus then waited until the hair grew back on slave s head prior to sending him off to his son-in-law. The second story also came from Herodotus, which claims that a soldier named Demeratus needed to send a message to Sparta that Xerxes intended to invade Greece. Back then, the writing medium was written on wax-covered tablet. Demeratus removed the wax from the tablet, wrote the secret message on the underlying wood, recovered the tablet with wax to make it appear as a blank tablet and finally sent the document without being detected. Invisible inks have always been a popular method of steganography. Ancient Romans used to write between lines using invisible inks based on available substances such as fruit juice and milk. When heated, the invisible inks would darken, and become legible. Ovid in his Art of Love suggests using milk to write invisibly. Later chemically affected sympathetic inks were developed. Invisible inks were used as recently as World War II. Modern invisible inks fluoresce under ultraviolet light and are used as anticounterfeit devices. For example, "VOID" is printed on checks and other official documents in an ink that appears under the strong ultraviolet light used for photocopies. II. PIXEL VALUE DIFFERENCING The gray-valued cover image is partitioned into nonoverlapping blocks of two consecutive pixels, states P i and P i+. From each block, we can obtain a difference value d i= P i-p i+ then d i ranges from 0 to 2. If d i is small, then the block is located within the smooth area and will embed less secret data. Otherwise, it is located on the edge area, and it can embed a greater amount of secret data. The quantization range table is designed with n contiguous ranges, and the range table ranges from 0 to 2. The number of secret bits hidden in two consecutive pixels depends on the quantization range table.[] The embedding algorithm is described as follows and procedure is given in figure. Step. Calculate the difference d i= P i-p i+ for each block of two consecutive pixels P i and P i+ Volume 7, Issue 2, 20 6
Step 2. Search the quantization range table for d i to determine how many bits will be embedded. Obtain the range R i in which R i =[L i, U i], where L i, and U i are the lower bound and the upper bound of R i, and t= Log(U i- L i) is the number of embedding bits. Step 3. Read m secret bits from the secret bit stream, and transform it into decimal value b. Step 4. Calculate the new difference d i = L i+secret message(decimal). Ensure both d i and d i are in the same range R i Step. Average d i to P i and P i+. The new pixel values P i and P i+ are obtained by the following formula where m = di di Table : The quantization range Fig : Procedure for Pixel Value Differencing Volume 7, Issue 2, 20 69
III. PROPOSED METHODOLOGY The proposed method is applied on color images by representing color image into three components named as Red, Green and Blue. These components are represented by pairs like red and green, green and blue. The pixel value difference algorithm is applied on each pair separately and the obtained values are readjusted to get stego red, green and blue components. Finally these components are concatenated to produce stego color Image. The algorithm used for embedding the data is as follows and the schematic diagram is shown in figure 2.. Represent the color image with R,G & B components 2. Form the pairs (R,G) and (G,B) 3. Consider the first pixel in Red component, first pixel of Green component and apply PVD algorithm 4. Repeat step-3 for entire red and green components. Repeat the step-3 and step-4 for Green and Blue components 6. Green component is in common between two pairs. Hence the modified pixel value of green component is the minimum of two values obtained from two pairs. Fig 2: schematic diagram of data-hiding IV. RESULTS AND DISCUSSION In this section, the results are provided for evaluating the performance of proposed technique. The proposed method tested on different color images and the performance is evaluated by using PSNR and information capacity. The original and stego images are given figure 3 and figure 4. The results are compared with existing technique and provided in the following table 2. It is found that the proposed method gives more information capacity in terms of bits than existing techniques. Volume 7, Issue 2, 20 70
Cover Image Lena Mandri l Jet Airpla ne Sailboa t Pepper s Table 2: Comparison of proposed method with existing techniques Swain s PVD Method Yang & Wang Mandal & Das proposed method Capacit PSN Capacit PSN Capacit PSN Capacit PSN y R y R y R y R (Bits) (db) (Bits) (db) (Bits) (db) (Bits) (db) 23439 4.2 23439 349 9660 4. 40.2 4 4 2 46.7 40640 2247 297 2367 37. 40.4 4 3.7 6 40.3 9660 33.29 9660 43.73 9660 47.4 9660 39.43 40640 2247 297 2367 37.4 40.64 39.3 40.37 4994 26769 0 42496 7 302 4.49 46. 47.29 47.06 Our proposed method Capacit y (Bits) 2030 6 223494 777 0 226060 2466 0 PSN R (db) 27.7 22.4 2.69 27.70 29.0 Volume 7, Issue 2, 20 7
Fig 3: s Fig 4: s V. CONCLUSION Pixel value differencing technique applied on Gray scale images for hiding data. Incase of color images, Pixel value differencing technique is applied on each component separately and then concatenated to generate RGB stego image. In this paper, Pixel value differencing technique on pairs on red and blue, blue and green components is applied to increase the information capacity but gives poor visible quality. Volume 7, Issue 2, 20 72
REFERENCES [].Hsien-Wen Tseng and Hui-Shih Leng A Steganographic Method Based on Pixel-Value Differencing and the Perfect Square Number, Journal of Applied Mathematics Volume 203 [2] Wu D-C, Tsai W-H. 2003 A steganographic method for images by pixel value differencing. Pattern Recognit. Lett. 24, 63 626. (doi:0.06/s067-6(02)00402-6) [3] Mandal JK, Das D. 202 Steganography using adaptive pixel value differencing (APVD) of gray images through exclusion of overflow/underflow. In 2nd Int. Conf. on Computer Science, Engineering and Applications (CCSEA-202), Delhi, India [4] Yang C-Y, Wang W-F. 20 Block based color image steganography using smart pixel-adjustment. Adv. Intell. Syst. Comput. 329, 4 4. (doi:0.007/97-3-39-226-_) [] Swain G. 206 Adaptive pixel value differencing steganography using both vertical and horizontal edges. Multimed. Tools Appl. 7, 3 4 3 6. (doi:0.007/s 042-0-2937-2) [6] Khodei M, Faez K. 202. New adaptive steganographic method using least significant bit substitution and pixel value differencing. IET Image Process 0, 667 66. (doi:0.049/iet-ipr.20.009). [7] Parvez MT, Gutub AA. 20. Vibrant color image steganography using channel differences and secret data distribution. Kuwait J. Sci. Eng. (KJSE) 3, 27 42. [] Nagaraj V, Vijayalakshmi V, Zayaraz G. 203. Colour image steganography based on pixel value modification method using modulus function. In 203 Int. Conf. on Electronic Engineering and Computer Science, pp. 7 24. [9] Prema C, Manimegalai D. 204. Adaptive color image steganography using intra color pixel value differencing. Aust. J. Basic Appl. Sci., 6 67. [0] Yang C-Y, Wang W-F. 20. Block based color image steganography using smart pixel-adjustment. Adv. Intell. Syst. Comput. 329, 4 4. (doi:0.007/97-3-39-226-_). [] Zhao W, Jie Z, Xin L, Qiaoyan W. 20. Data embedding based on pixel value differencing and modulus function using indeterminate equation. J. China Univ. Posts Telecommun. 22, 9 00. (doi:0.06/s00- ()6063-). Volume 7, Issue 2, 20 73