Lsb Matching

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  • Topic: Steganography, Color, Least significant bit
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  • Published : November 19, 2010
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SLSB: Improving the Steganographic Algorithm LSB
Juan José Roque, Jesús María Minguet
Universidad Nacional de Educación a Distancia (Spain) juanjose.roque@extremadura.es; jminguet@issi.uned.es

Abstract. This paper presents a novel steganographic algorithm based on the spatial domain: Selected Least Significant Bits (SLSB). It works with the least significant bits of one of the pixel color components in the image and changes them according to the message’s bits to hide. The rest of bits in the pixel color component selected are also changed in order get the nearest color to the original one in the scale of colors. This new method has been compared with others that work in the spatial domain and the great difference is the fact that the LSBs bits of every pixel color component are not used to embed the message, just those from pixel color component selected. Keywords: Security, Steganography, Least Significant Bit.

1

Introduction

The steganography can be considered as a branch of cryptography that tries to hide messages within others, avoiding the perception that there is some kind of message. To apply steganographic techniques cover files of any kind can be used, although archives of image, sound or video files are the most used today. Similarly, information to hide can be anything: text, image, video, sound, etc. There are two trends at the time to implement steganographic algorithms: the methods that work in the spatial domain (altering the desired characteristics on the file itself) and the methods that work in the transform domain (performing a series of changes to the cover image before hiding information. To select the best areas the Discrete Cosine Transform DCT, Wavelet Transform, etc. are used). While the algorithms that work in the transform domain are more robust, that is, more resistant to attacks, the algorithms that work in the spatial domain are simpler and faster. The best known steganographic method that works in the spatial domain is the LSB [1] (Least Significant Bit), which replaces the least significant bits of pixels selected to hide the information. This method has several implementation versions that improve the algorithm in certain aspects [2][3][4][5][6][7]. This paper proposes a new method, SLSB (Selected Least Significant Bit), that improves the performance of the method LSB hiding information in only one of the three colors at each pixel of the cover image. To select the color it uses a Sample Pairs analysis, given that this analysis is more effective to detect hidden information. Finally, applies a LSB Match [8] method so that the final color is as close as possible to the original one in the scale of colors. The paper is organized as follows. Section 2 gives a brief classification of the steganographic methods that works in spatial domain. Section 3 describes the

proposed method. Section 4 is on the experimental results, followed by conclusions at Section 5.

2

Methods in Spatial Domain

A basic classification of steganographic algorithms operating in the spatial domain as the method for selecting the pixels distinguishes three main types: non-filtering algorithms, randomized algorithms and filtering algorithms. 2.1 Non-filtering Algorithm This is the simplest steganographic method based in the use of LSB, and therefore the most vulnerable. The embedding process consists of the sequential substitution of each least significant bit of the image pixel for each bit of the message. For its simplicity, this method can camouflage a great volume of information [9]. This technique is quite simple. It is necessary only a sequential LSB reading, starting from the first image pixel, to extract the secret message. This method also generates an unbalanced distribution of the changed pixels, because the message is embedded at the first pixels of the image, leaving unchanged the remaining pixels. 2.2 Randomized Algorithm This technique was born as a solution for the problems of the...
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