Abstract. Steganography is an art of hiding information. There are several existing approaches, of which LSB is the popular known technique. While performing ...
Zero Distortion Technique: An Approach to Image Steganography Using Strength of Indexed Based Chaotic Sequence Shivani Sharma1, Virendra Kumar Yadav1, and Saumya Batham2 1 Computer Science Dept., MCA Dept., ABES-EC, Ghaziabad, Uttar Pradesh, India {shivanisharma2804,virendrashines,saumyabatham003}@gmail.com 2
Abstract. Steganography is an art of hiding information. There are several existing approaches, of which LSB is the popular known technique. While performing image steganography, there are certain limitations, in terms of time, robustness, distortion, quantity of data to hide etc. A common major limitation involved in these approaches is: altering the pixel value of the image which leads to distortion in the cover image. It can be easily detected by histogram and PSNR value. Zero Distortion Technique (ZDT) is proposed to overcome the limitation, as no changes are reflected in the histogram and PSNR value of the cover and the stego image. Experimental results on certain images shows that the proposed algorithm gives refine results. The proposed technique is robust, fast and helpful in providing security to our confidential data. Keywords: Steganography, Zero Distortion Technique (ZDT), steganalysis, LSB technique, cryptography, chaotic sequence, logistic maps.
1
Introduction
In today's era of internet it is difficult to provide privacy while sending any confidential information. There are many existing techniques which helps individuals in providing security to their data but only up to some extent. In the era of digital world, we have to think twice while sending our data to the other end, as there are many third parties in between, who are trying to retrieve data by unauthorized means. On the other hand, these techniques have their own limitations. Some of them are: quantity of data, robustness, distortion, time constraint and many more. One of the famous techniques known is LSB technique but it has its own limitations. It is bounded by the quantity of data we can send. In this technique we focus on the last bit only for hiding our data. Data hiding can be broadly classified into three categories i.e. steganography, watermarking and cryptography [1]. Cryptography is basically used to encrypt data so that it can’t be understood by the intruder while steganography and watermarking is done to hide data. Watermarking make data authenticated by making a special mark to show owner's identity. It is mainly used for copyright purpose [2]. J. Lloret Mauri et al. (Eds.): SSCC 2014, CCIS 467, pp. 472–481, 2014. © Springer-Verlag Berlin Heidelberg 2014
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Steganography is derived from a Greek word meaning 'concealed writing'. It has been widely used in ancient times also viz. tattoo, wax coating etc [9]. It is used to provide confidentiality to our data. Steganography is an emerging field for information security which is booming because of its vast features and techniques [10]. One of the advantages of steganography is that it does not attract the attention of steganalyst. Steganalysis is a technique of detecting hidden message from the stego image and steganalyst is the person which performs steganalysis. When steganography is applied on the cover image, it becomes stego image (an image containing hidden data).The image in which we are hiding data is known as cover image. In this technique we can use any image i.e. color, grey, black and white as the cover image. We can hide data in any of the 3 mediums - image, audio and video. While applying steganography, we must assure that distortion in the original image will be less so that it can't be detected by the steganalysis attack. The technique we are using should also emphasize on achieving optimal amount of data to be hidden in the stego image.
Fig. 1. Schematic diagram of Steganography
This work is organized as follows: In section 2, we have discussed a brief overview of related work done in the area of steganography. In section 3, we have discussed the proposed section 3.1, section3.1, section 3.2, section 3.3 which describes about Zero Distortion Technique, Encryption Technique, technique for embedding and extracting text from image using Zero Distortion Technique, Execution of algorithm for embedding text data into image and extracting text data from image using Zero Distortion Technique respectively and Section 4 presents figures and tables of proposed work. In last we have presented the experimental results.
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Related Work
2.1
LSB Technique
Alaa A. Jabbar Altaay [9] in this paper author has categorized steganography techniques into two major types like Fragile Steganography, Robust Steganography. Fragile method means insertion of information in a medium in such a way that modification in the host file will destroy the whole embedded information. In contrast bits manipulation of robust methods will not easily be removed from host file. There are several techniques used in steganography one most the most simple and widely used technique known is LSB [3]. In LSB (Least Significant Bit) as the name
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suggests we make changes in the least significant bit only. The LSB is chosen for steganography because there will be a slight change in the cover image as only the last significant bit is replaced by the data bit. It has been widely used because of its simplicity.LSB technique has some limitations also, as the resultant image become distorted [4]. The distortion in the cover image is visible to human eye and can also be seen with the help of histogram and PSNR value, we can hide a very little amount of data as we are making changes in the LSB only [5].LSB is mostly associated with the format JPEG, and steganalyst can extract our message very easily i.e. vulnerable to attacks.
Fig. 2. Implementation of LSB Technique
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Proposed Work
3.1
Zero Distortion Technique
In this paper we suggest a technique which leads to zero distortion. In other words we can say that we are extracting bits from the cover image in order to generate the text which we want to hide. We are storing the location bits which are matched with the data bit of the text which we want to hide. These location bits are in matrix form consists of binary bits i.e. 0 and 1, we than convert these binary bits into decimal format by which we get the ASCII value of the characters. Converting these ASCII value to characters we get our text data. There is no need to draw histogram and to calculate the PSNR value as we are not changing a single bit of the cover image. PSNR value is used to calculate the ratio between the signal (i.e. original image) and the noise involve during the compression of image. But as we are not compressing the image so we don’t have to calculate it. Histogram is the representation of distribution of data on graph. Through histogram we can easily detect the changes done in the cover image. As this technique involves zero distortion it will be highly efficient while passing confidential data to the other end. Another feature of this technique is that we can hide a large amount of data, as we don’t restrict ourselves to a particular row or column. To provide more security, encryption of the matrix of the location has been performed, which will randomize the value of matrix, so that it cannot be detected by the steganalysis. The stego image, chaotic sequence and the value of X0 and µ will be passed to the receiver end from which text data will be extracted.
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Fig. 3. Embedding of text into image
3.2
Encryption Technique
Chaos is a state of irregularity and disorder which makes the situation more complex to handle .Chaotic sequence has been used in the field of cryptography for providing randomness to the data so that it will become more secure [6]. Chaotic sequences and the word random can be used interchangeably. Properties of chaotic sequence which makes it more powerful are: • Unpredictability • In decomposability • Element of regularity
Fig. 4. Bifurcation Diagram for logistic map
The system shows different behavior for different range of . Some of them are shown below: • For 0 < < 1 the output of the system is zero irrespective of the initial condition. • For 1 < < 3 the system reaches a steady state. • For 3 < < 1+ (approximately = 3.45) the system oscillates between two values.
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• For > 1+ the system oscillates between infinite values and shows chaotic behavior. • Beyond = 4, the values eventually leave the interval [0,1] and diverge for almost all initial values. Thus logistic map acts as an excellent chaotic system [8]. A chaotic system exhibits a great sensitivity to initial conditions. The logistic map shows this chaotic behavior for values of between 3.57 and 4. Chaotic sequence is so random that changing a single bit varies the sequence up to a large extent. The value generated by the chaotic sequence varies in the time interval of [0, 1].
Calculation of the values of the sequence will be carried out by using the following equation. Xn+1=µ * Xn * (1-Xn)
(1)
Here the value of µ is constant. Initially we fix the value of X0 in the range of [0, 1].
We had randomized the matrix of locations by using chaotic sequence [7]. 3.3
Techniques for Embedding and Extracting Text from Image Using ZeroDistortion Technique
With contrast to the earlier technique of LSB, we suggested this technique so that no distortion will be there in the image as it happens in the LSB technique. 3.3.1 Proposed Algorithm for Embedding Text into Image This technique will embed the input text input image without changing any pixel value of the image. INPUT: A cover image (grey) (I0), an input text (T0). OUTPUT: Chaotic sequence (C0s) and stego-image (IS). 1) Read the cover image (I0) and the input text (T0). 2) Convert the cover image (I0) into binary format and text data (T0) to ASCII format and then into binary format. 3) Convert the matrix of text data (T0) into a column vector. 4) For all i=1 to 8 repeat steps 4 to 8 5) Match the bits of text data (i.e. column vector) with the bits of the cover image (I0).
Zero Distortion Technique: An Approach to Image Steganography
6) If matched then save the location value in a matrix of n rows and 8 columns is the length of the text. 7) Increase count variable and location by 1. 8) Else increase the location. // resulting is the matrix of location (L0S).Perform encryption on L0S by using chaotic sequence approach [7]. Calculate the dimension of matrix of location (L0S) m x n, where m is the rows and n is the column. 9) Set X0 value in the range of 0-1, and value of µ in the range of 3.5–4 10) For i=1 to m x n 11) Apply the equation (1) for generating chaotic sequence 12) Sort the values generated by the above formula and extract the index of the sequence. 13) Reshape the indexes into m x n matrix same as the dimension of matrix of location (L0S). //This is the chaotic sequence i.e. C0S which will be passed to the decryption side. 14) If count equals length of the text then text has been successfully embedded into image. 15) Else text has not been successfully embedded into image. 16) Display the stego-image (IS). 3.3.2 Proposed Algorithm for Extracting Text from Image This algorithm will extract the hidden text (T0) from the stego image (Is). INPUT: Chaotic sequence (C0s), value of X0 and µ , stego image (Is). OUTPUT: Embedded input text (T0) 1) Extract the matrix of location (L0S) from the chaotic sequence by using the same formula. //Decryption has been performed 2) Convert the stego image (Is) pixels into binary format. 3) For i=1 to length of the image Repeat step from 3 to 5. 4) Match the image location and value of the matrix of locations of stego image (L0s). 5) If matched then save the value at that location of the image in an array. 6) Else the location of the image is increased. 7) Convert the array into decimal format i.e. the ASCII value of the embedded text. 8) Convert the ASCII value into characters and transpose it. 9) Embedded text will be displayed i.e. T0.
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Figures and Tables
4.1
Figures Shows the Schematic Diagram of the Zero Distortion Technique
Fig. 4(a). Schematic diagrams (embedding text)
4.2
Fig. 4(b). Schematic diagrams (extracting text)
Comparision of LSB and ZERO – Distortion Technique
Comparison is based on the text length that we can hide in the image and time elapsed in hiding the text data. It is performed on various types of formats like jpg, png, tif etc. Table 1. LSB technique
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Table 2. ZDT technique
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Conclusions and Future Research Direction
In this paper we have presented a technique ZDT. Resulting image obtained after implementation of ZDT will reflect no changes as compared to the original image. As there is no changes, no issue of detecting with human eyes, by histogram or PSNR value will reflect. Proposed technique can be applied to any type of file formats and we can hide a huge amount of data. Data is more secure as encryption technique chaotic sequence has been used. ZDT algorithm can be considered as efficient algorithm in terms of time, capacity in comparison to LSB technique. Future scope in this direction includes developing efficient algorithms in terms of time, space and of course in terms capacity of hiding and their strength to conceal the data within it.
References 1. Stalling, W.: Cryptography and network security: Principles and Practices, 4th edn. Prentice (2006), ISBN – 978-81-775-8774-6 2. Das, S., Bandyopadhyay, P., Paul, S.: A New Introduction towards Invisible Image Watermarking on Color Images. In: IEEE International Advance Computing Conference (IACC 2009) (2009) 3. Neeta, D., Snehal, K., Jacob, D.: Implementation of LSB Steganography and its evaluation for various bits 4. Juneja, M., Sandu, P.S.: Designing of Robust Image Steganography Technique Based on LSB Insertion and Encryption. In: International Conference on Advances in Recent Technologies in Communication and Computing (2009) 5. Alam, S., Zakariya, S.M., Rafiq, M.Q.: Analysis of modified LSB Approaches of Hiding Information in Digital Images. In: 5th International Conference on Computational Intelligence and Communication Networks 2013 (2013)
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6. Acharya, A.K.: Image Encryption Using A Chaos Base Encryption Algorithm. In: International Conference on Commmunication, Computing and Security (ICCCS 2011) (2011), http://dl.acm.org/citation.cfm?id=1948060 7. Batham, S., Acharya, A.K., Yadav, V.K., Paul, R.: A New Video Encryption Algorithm Based on Index Based Chaotic Sequence. In: Confluence 2013 (2013) 8. Soni, A., Acharya, A.K.: A Novel Image Encryption Approach Using an Index Based Chaos and DNA Encoding and its Performance Analysis. IJCA (0975-8887) 47(23) (June 2012) 9. Altaay, A.A.J., Sahib, S.B., Zamani, M.: An Introduction to Image Steganography Techniques. In: International Conference on Advanced Computer Science Applications and Technologies 2012 (2012) 10. Gupta, S., Goyal, A., Bhushan, B.: Information Hiding Using Least Significant Bit Steganography and Crptography. I. J. MECS 2012 (2012) 11. Paul, R., Acharya, A., Yadav, V.K., Batham, S.: Hiding Large Amount of Data using a New Approach of Video Steganography. In: CONFLUENCE 2013, IET digital library (2013)
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Experimental Results
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