Data Security using Data Hiding

S .K. Moon PICT, Pune,

INDIA

R.S. Kawitkar SCOE, Pune,

INDIA

Abstract

For Stenography we have used the least significant bit (4LSB) substitution method [2]. The 4LSB method is implemented for color bitmap images (24 bit and 8 bit i.e. 256 color palette images) and wave files as the carrier media. “The goal of Stegnography is to hide messages inside other harmless messages in a way that does not allow any enemy to even detect that there is a second secret message present.” By using this proposed algorithm, we can hide our file of any format in an image and audio file. We can then send the image via e-mail attachment or post it on the web site and anyone with knowledge that it contains secret information, and who is in possession of the encryption password, will be able to open the file, extract the secret information and decrypt it. Keywords: Image Stegnography, audio Stegnography, security, cryptography, and, 4LSB 1. Introduction

Stenography literally means covered writing. Its goal is to hide the fact that communication is taking place. In the field of Stenography, some terminology has been developed. The term cover is used to describe the original, innocent message, data, audio, still, video and so on. The growing possibilities of modem communications need the special means of security especially on computer network. The network security is becoming more important as the number of data being exchanged on the Internet increases. Therefore, the confidentiality and data integrity are required to protect against unauthorized access. This has resulted in an explosive growth of the field of information hiding. In addition, the rapid growth of publishing and broadcasting technology also requires an alterative solution in hiding information. The copyright of digital media such as audio, video and other media available in digital form may lead to large-scale unauthorized copying. This is because the digital formats make it possible to provide high image quality even under multi-copying. Unauthorized copying is of great problem of especially to the music, film, book and software publishing industries. To overcome this problem, some invisible information can be embedded in the digital media in such a way that it could not be easily extracted without a specialized technique [1]. Information hiding is an emerging research area, which encompasses applications such as copyright protection for digital media, watermarking, fingerprinting, and Stenography .All these applications of information hiding are quite diverse. In watermarking applications, the message contains information such as owner identification and a digital time stamp, which is usually applied for copyright protection. This adds to copyright information and makes it possible to trace any unauthorized used of the data set. Stenography hides the secret message within the host data set and its presence is imperceptible [9].

International Conference on Computational Intelligence and Multimedia Applications 2007

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International Conference on Computational Intelligence and Multimedia Applications 2007

0-7695-3050-8/07 $25.00 © 2007 IEEEDOI 10.1109/ICCIMA.2007.163

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Fig.1 shows the Stenographic system in which cover image is 24 /8 bit BMP image. BMP image is lossless image means there is no difference between cover image and stego image. In BMP image there are large numbers of color, which is advantage of BMP. As we are using 4LSB insertion method to hide, the text behind the cover image is suitable for BMP image. If the text is large, compression and encryption techniques are used so that it take less space of the pixel [7]. 2. LSB insertion method The least significant bit insertion method is probably the most well known image Stenography technique. It is a common, simple approach to embed information in a graphical image file. Unfortunately, it is extremely vulnerable to attacks, such as image manipulation. A simple conversion from a GIF or BMP format to a lossy compression format such as JPEG can destroy the hidden information in the image. When applying4LSB techniques to each bytes of a 8-bit image, one bit can be encoded to each pixel. Any changes in the pixel bits will be indiscernible to the human eye. The main advantage of 4LSB insertion is that data can be hidden in the last four least significant bits of pixel and still the human eye would be unable to notice it. Care needs to be taken in the selection of the cover image, so that changes to the data will not be visible in the stego-image 3]

Fig. 2 Block diagram of 4 LSB insertion method of extracting text form image

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Fig. 3

AUDIO

LSB Coding Least significant bit (LSB) coding is the simplest way to embed information in a digital audio file. By substituting the least significant bit of each sampling point with a binary message, LSB coding allows for a large amount of data to be encoded[8] In LSB coding, the ideal data transmission rate is 1 kbps per 1 kHZ. In some implementations of LSB coding, however, the two least significant bits of a sample are replaced with two message bits. This increases the amount of data that can be encoded but also increases the amount of resulting noise in the audio file as well. Thus, one should consider the signal content before deciding on the LSB operation to use. For example, a sound file that was recorded in a bustling subway station would mask low-bit encoding noise. On the other hand, the same noise would be audible in a sound file containing a piano solo.[4]. To extract a secret message from an LSB encoded sound file, the receiver needs access to the sequence of sample indices used in the embedding process. Normally, the length of the secret message to be encoded is smaller than the total number of samples in a sound file. One must decide then on how to choose the subset of samples that will contain the secret message and communicate that decision to the receiver.[11] One trivial technique is to start at the beginning of the sound file and perform LSB coding until the message has been completely embedded, leaving the remaining samples unchanged. This creates a security problem, however in that the first part of the sound file will have different statistical properties than the second part of the sound file that was not modified. One solution to this problem is to pad the secret message with random bits so that the length of the message is equal to the total number of samples. Yet now the embedding process ends up changing far more samples than the transmission of the secret required. This increases the probability that a would-be attacker will suspect secret communication [10][5] .

3. How security is enforced in the proposed algorithm

The stego image file along with the message embedded into it is available to the hacker. The stego file does not reveal any difference in attributes like size, content etc., from that of the original file. Hence it is difficult for a hacker to find out that this image contains a message.

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Even if he doubts so, he has to apply the same algorithm to retrieve the embedded file. [10] Unfortunately if he finds out the algorithm by which the text has been embedded into the medium, he could get back only the cipher text file. In the retrieved file, he could see nothing but the junk characters. This provides an extra layer of protection. To get the original message, this junk file has to be decrypted with the encryption algorithm with the correct password. This also adds an extra layer of Protection. If the algorithm is found out, he must supply the correct password to get the correct message [9]. 4. Results

Cover Image Stego Image

Fig. 4

5. Conclusion

In this paper we focus our concern in image because of it’s widely used in Internet and also in mobile system. And based on our study, 4-LSB substitutions is a good method for embedding an acceptable amount of data, that’s because size of embedded message to carrier’s size.4 LSB embedded data, can easily be implemented and do not visually degrade the image to the point of being noticeable. Furthermore the encoded message can be easily recovered and

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even altered by a 3rd party. It would appear that 4 LSB is good method of Stegnography due to its tremendous information capacity, less error and more secured. Using 4-LSB methods we can exchange secret messages over public channel in a safe way. [6][7] References

[1]. R.J. Anderson and F. A. P. Petitcolas (2001) On the limits of the Stegnography, IEEE Journal Selected

Areas in Communications, 16(4), pp. 474-481. [2]. ] J.Fridrich, M.Goljan, and R.Du,”Detecting LSB Stegnography in Color and Gray –Scale Images”,

Magazine of IEEE Multimedia, Special Issue on Security, October-November issue, 2001,pp.22-28. [3]. T. Cedric, R. Adi and I. Mcloughlin (2000), Data concealment in audio using a nonlinear frequency

distribution of PRBS coded data and frequency-domain LSB insertion, [4]. Proc. IEEE International Conference on Electrical and Electronic Technology, Kuala Lumpur, Malaysia,

pp. 275-278. [5]. Y. Lee and L. Chen (2000) High capacity image steganographic model, IEE Proceedings on Vision,

Image and Signal Processing, 147(3), pp. 288-294. [6]. S. K. Moon, V. N. Vasnik, “Application of steganography on image file”, National conference on Recent

trends in Electronics, pp. 179-185. [7]. Alkhraisat Habes, “Information transmissions in computer network. Information hiding in bmp image

Implementation analysis and evaluation” (Jan.2006) [8]. P. Bassia, I. Pitas and N. Nikolaidis (2001) Robust audio watermarking in the time domain, IEEE

Transactions on Multimedia, 3(2), pp. 232-241. [9]. S. Dumitrescu, W.X.Wu and N. Memon (2002) On steganalysis of random LSB embedding in

continuous-tone images, Proc. International Conference on Image Processing, Rochester, NY, pp. 641-644.

[10]. William Stallings, Cryptography and Network Security, Principles and Practice, Third edition, Pearson Education, Singapore, 2003.

[11]. Hide & Seek: An Introduction to Stegnography: http:\\niels.xtdnet.nl/papers/practical.pdf.

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