A NOVEL METHOD FOR HIDING INFORMATION Samer Thaaban Abaas Al-Shibley Education College, Kufa University samir-alshebly@uokufa.edu.iq Abstract In this paper, we introduce a new method to hide information in an image, the sequence of hiding message bits in the cover pixels and the number of bits used for hiding information are differ from one block to another and depend on the gray scale values of the pixels in the center of cover image blocks. The proposed system like all steganography system consists of two stages. The first stage used for hiding message by using two keys, the first one used for determining the sequence that will be used in hiding message pixels, while the second key used to select the number of least significant bits in the cover image that will be used in hiding information. The second stage used for extracting and retrieving message information and reconstruct the message image precisely. Keywords: Steganography, hiding information, stego image, cover. I. INTRODUCTION Steganography is the art and science of hiding information in a deterministic sequence to prevent any person from detecting the hiding Information without authentication, the secret Information is embedded in a digital file by using a suitable algorithm, there are two types of materials existing in steganography system which are the message and the carrier (cover), Message is the secret Information that should be hidden and carrier is the material that takes the message in it according to steganography algorithm and keys. The file produced after hiding the message in the cover is called stego object that translated from the source of the message to its destination. There are many applications for steganography which are military, diplomatic, and personal applications. There are three related principles that determining the effectiveness of steganography algorithm which are 1- The size of the message file. - The difficulty of detecting the message. 3- The difficulty of altering the message by simple changing in the cover file Steganography can be classified into three types as illustrated in figure (1) II. ACCORDING TO COVER FILE TYPE Text steganography. Image steganography. Audio steganography. Video steganography. Image Steganography can be classified into three types a) Least Significant Bits (): Blind hide algorithm. Hide seek algorithm. Filter first algorithm. Battle steg algorithm. b) Masking and filtering techniques, take a different approach to hiding a message. These methods are effectively similar to paper watermarks, creating markings in an image. This can be achieved for example by modifying the luminance of parts of the image. While masking does change the visible properties of an image, it can be done in such a way that the human eye will not notice the anomalies. c) Transform Domain techniques utilize an algorithm such as the Discrete Cosine Transformation (DCT) or wavelet transformation to hide information in significant areas of the image. III. According to the type of the steganography key: IV. PROPOSED SYSTEM Pure steganography. Secret key steganography. In generl,the proposed system as illustrated in figure () consist of two steges, the first one is Message hiding stage and the second stage is message extracting from the stego object 107 P a g e
Steganography Classification according to cover file type Classification according to how the information has been hidden Classification according to the type of the key Pure Secret Key Public Key Insertion Substitution Generation Text Image Audio Video Line shift Word shift Feature Parity Phase SS Echo Masking and filtering Transformation Blind hide Hide seek Filter first Battle steg 108 P a g e
Cover (Image) Divided into non overlap blocks with size (3 3) Message hiding stage Figure (1) classification of steganography systems Message (Image) Check the value of three of each pixel in the center of the block a. message hiding stage this stage is divided into the following steps:- 1- Divided cover image into non overlap blocks with size (3 3) pixels. - Check the three of the pixel in the center of each block (TLSBS). 3- Hiding the message in each pixel in the blocks except the centers as illustrated in figure (3) to produce stego object. (= 0) Hiding in two bits by starting from top left corner (= 1) Hiding in one bit by starting from top left corner (= ) Hiding in two bits by starting from down right corner (= 3) Hiding in one bit by starting from down right corner (= 4) Hiding in two bits by starting from down left corner (= 5) Hiding in one bit by starting from down left corner (= 6) Hiding in two bits by starting from top right corner (= 7) Hiding in one bit by starting from top right corner 1 3 1 3 4 5 6 4 5 6 7 8 9 7 8 9 Case (1) TLSB = 0 Case () TLSB = 1 NBITS = 9 8 7 9 8 7 6 5 4 6 5 4 3 1 3 1 Case (3) TLSB = Case (4) TLSB = 3 NBITS = 7 8 9 7 8 9 4 5 6 4 5 6 1 3 1 3 Stego image Message extracting stage Case (5) TLSB = 4 Case (6) TLSB = 5 NBITS = Divided into non overlap blocks with size (3 3) Apply inverse proposed hiding algorithm to extract message from stego image 3 1 3 1 6 5 4 6 5 4 9 8 7 9 8 7 Case (7) TLSB = 6 NBITS = Case (8) TLSB = 7 Image Messag e Figure () block diagram of the proposed system figure (3) 109 P a g e
Figure (3) the direction of hiding information and number of bits for eight cases of variable (TLSBS) Where NBITS is the number of bits used in hiding information. TLSB is the value of three least significant bits. In addition to above operations in hiding stage, hiding information starting by substituting message bits in cover blocks with (TLSBS = 0) then in blocks with (TLSBS = 1) and so on. This make hiding operation progress in random fashion. If the message pixels are (104, 18 ), this mean (01101000, 10000000,.), and the cover block is 190 00 10 185 0 07 180 190 00 1- Divided stego object image into non overlap blocks with size (3 3) pixels. - Check the three of the pixel in the center of each block (TLSBS). 3- Extracting the message in each pixel in the blocks except the centers as illustrated in figure (3). For the same block resulted in hiding stage the center of block (0) represented in binary as 1 1 0 0 1 0 1 0 The variable (TLSBTS= ), so case 3 will be applied to extract message bits as follow 01 1 1 0 0 1 0 0 1 190 1 0 1 1 1 1 1 0 18 1 0 1 1 0 1 1 0 TLSBS =, so case (3) will be applied, Then the numbers are represented in binary as 0 1 1 0 0 1 0 1 0 Values Before hiding Before After Values After hiding 00 1 1 0 0 1 0 0 0 0 1 01 190 1 0 1 1 1 1 1 0 1 0 190 180 1 0 1 1 0 1 0 0 1 0 18 07 1 1 0 0 1 1 1 1 0 0 04 185 1 0 1 1 1 0 0 1 1 0 186 10 1 1 0 1 0 0 1 0 0 0 08 00 1 1 0 0 1 0 0 0 0 0 00 190 1 0 1 1 1 1 1 0 0 0 188 At the end this block becomes 188 00 08 186 0 04 18 190 01 b. Message extracting stage 04 1 1 0 0 1 1 0 0 186 1 0 1 1 1 0 1 0 08 1 1 0 1 0 0 0 0 00 1 1 0 0 1 0 0 0 188 1 0 1 1 1 1 0 0 Te message bits are ( 01 10 10 00 (104, 18) V. RESULTS 10 00 00 00 ) that mean 1- The cover image is gray scale image of size (55 340) pixels, while message is gray scale image of size (144 144) pixels, the peak signal to noise ratio is (47) which calculated by applying the following equation SNR log ( l1) 10 peak 10 n 1 1 m1 [ g( r, c) I( r, c)] n m r 0 c0 Where, l is the number of gray levels in cover image. I(r,c) are the pixels before embedding process in cover image. g(r,c) are the pixels after embedding process in stego image. n,m are the width and height of cover image respectively. Figure (4) result (1) of the proposed system (1) This stage consist of the following steps 110 P a g e
a- Original image b - Message b- Message c- Stego image - The cover image is gray scale image of size (56 384) pixels, while message is gray scale image of size (136 93) pixels, the peak signal to noise ratio is (46) Figure (5) result () of the proposed system a- Stego image 3-The cover image is gray scale image with size of (56 56) pixels, while the message is gray scale image with size of (10 10) pixels, the peak signal to noise ratio is (45.5) Figure (6) result (3) of the proposed system a- Original image a- Original image 111 P a g e
b - Message REFERENCES [1]- Eric Cole, and Ronald D. Krutz " Hiding in Plain Sight: Steganography and the Art of Covert Communication", Wiley Publishing USA, 003. b- Stego image VI. CONCLUSIONS The size of message cannot be expected from the size of the cover image because it depends on the values of pixel in the center of the blocks. The change in cover image is unnoticeable therefore peak signal to noise ratio in high rate. The number of bits used in hiding information change from one block to another, the direction of hiding message bits also change from one block to another, and the blocks are not used in sequential arrange, so information may be hidden in last block before the first one in the same row, these features make this algorithm strong against the attackers. []- Sabu M Thampi "Information Hiding Techniques: A Tutorial Review" Department of Computer Science & Engineering LBS College of Engineering, Kasaragod Kerala, India, 004. [3]- Samir K Bandyopadhyay, Debnath Bhattacharyya, Debashis Ganguly, Swarnendu Mukherjeeand Poulami Das "A Tutorial Review on Steganography",University of Calcutta,008. [4]- Dr.M.Umamaheswari, Prof.S. Sivasubramanian, and S.Pandiarajan "Analysis of Different Steganographic Algorithms for Secured Data Hiding", IJCSNS International Journal of Computer Science and Network Security, 010. [5]- Shrikant s. khaire, and dr.sanjay l.nalbalwar "Review: Steganography Bit Plane Complexity Segmentation (BPCS) Technique " International Journal of Engineering Science and Technology, 010. 11 P a g e