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A Best Fit Strategic Approach for Sample Selections of a Carrier to Minimizing Quantization Error

Virendra P. Nikam1* and Shital S. Dhande 2

Sipna College of Engineering and Technology, Amravati, Amravati, Maharashtra, India

Abstract

Today data security and its transmission over the wireless network need special attention. An intruder always has a watch on sensitive data transmitted over a wireless network. This work proposes an approach that minimizes the quantization error between the original and result carrier by selecting optimize samples during Data Hiding. The proposed work finds out the best matching carrier components during the data hiding process. Results also imply that achieved results are far better than any other steganographic method.

Keywords: Best fit strategy, steganography, quantization error, carrier object, transmission media, data hiding, data extraction, etc.

1.1 Introduction

Information security is a primary focus for every IT industry. Most of the industries are grown up by analyzing the data that they have. Data is any sort of raw material which can be processed to generate valuable information. Millions of dollars are spent on data security in almost all industries in India and all over the world. In the past 10 years, information security has become a vital domain that needs special attention in every sector. Raw data is a base pillar of any IT industry. Recent history shows that most industries have failed to recover because they do not have a proper backup facility. In 2005, a major flood in Mumbai stopped the functioning of more than 2,000 small-scale IT industries. This implies that the security of information or raw data is very much important. Without security, it is not possible for any IT industry to grow fast and within the expected time.

Now the major issue that comes into focus is how to provide security to sensitive data of an industry. There are many techniques available that are best to provide security to data which is stored either on a separate server system or on a local server system. Many IT Industries prefer to store their data on the server system. Server systems have their own security features and protocols which are enough to protect data. But from the financial point of view, it is not convenient to maintain a separate server to stored data especially for those industries which have an annual turnover between 1 and 5 lakh.

The common techniques used to provide security to data are cryptography, steganography and watermarking. These three techniques have their own applicability and limitations.

1.1.1 Cryptography

Cryptography is an art to convert readable data into an unreadable format. It totally hides the meaning of the original data. The process of converting readable data into unreadable format is called as encryption, whereas converting unreadable data into a readable format is called decryption. To perform encryption and decryption, sender and receiver use either the same or a different key. Based on the similarity of the key used at sender and receiver side, cryptography is classified as, i) private key cryptography, and ii) public key cryptography. Public key cryptography uses separate keys for encryption and decryption. The algorithms like RC2, data Encryption standard, triple Data Encryption standard, advanced encryption standard comes under the category of private key cryptography, whereas algorithm like RSA comes under public key cryptography. Cryptography converts readable data set {p1,p2,p3,p4,p5....,pn} into unreadable(encrypted) data set {e1,e2,e3,e4,e5....,en }. Cryptography can be defined as f(x) = f(p,k) for encryption and f(x) = f(f´(x),k) for decryption.

1.1.2 Steganography

It is an art of hiding/concealing secret pieces of information behind a carrier object. It completely hides the existence of data with the help of carrier media. There is a considerable similarity between cryptography and steganography; both hide the real presence of data to an unauthorized user. The result of steganography is exactly similar in appearance with the original carrier object. This is the one mandatory feature of steganography which does not allow any change to occur in carrier object. Steganography takes one carrier object fc & secret data fd and hides it behind carrier object f(H) = f(f(c),f(d)). The similarity of the resulting stego object can be measured with parameters like peak signal to noise ratio (PSNR), mean square error (MSE), absolute difference, structural content, mean difference, normalized absolute error (NAE) and others. If the result object finds dissimilar visual perceptual quality with original carrier object f(c) ? f(H), the process is not called steganography.

1.1.3 Watermarking

It is generally used for copyright protection. A few authors also call watermarking as steganography. Watermarking is of two types: i) visible watermarking, and ii) invisible watermarking. Figure 1.1 shows about the structure highlighting overview of cryptography. In watermarking, the original carrier is replaced with watermark data bits. It is completely changed carrier object especially in visible watermarking. The concept of watermarking was originally designed for copyright protection; later on it was expanded for secret data hiding and transmission. This paper focuses on Data Hiding and extraction mechanism by optimizing sample selections approach for minimizing quantization error. Quantization error is the difference between result stego object and original carrier object Qe = |Co - Cr|. Many existing steganography techniques do not focus on minimizing quantization error. Existing techniques directly select sample irrespective of its value that results in large quantization error. Maximum quantization error can create difference among original and result carrier object. This paper has a primary focus on effective sample selections with minimum difference.

Figure 1.1 Overview of cryptography.

Basic questions come into mind, such as "How to select optimize sample during Data Hiding process?" This paper proposes an algorithm that finds the best matching carrier sample using the best fit strategic approach. Figure 1.2 shows about the structure highlighting overview of steganography. The best fit strategic approach is one that is generally used in memory allocation. While allocating memory, a primary focus is given to memory fragmentation. Memory gets fragmented when memory block of either larger or smaller size get allocated to the required content. The best fit strategic approach reduces memory fragmentation and hence it is a good choice by memory allocator. The best bit strategic approach is chosen by many programmers due to its effective selection of required memory block from available blocks of memory. Consider an item set {i1,i2,i3,i4,i5....,in} and the required item to search is {si} At very first stage, difference among {si} and item set please find out {|i1 - si|,|i2 -si|,|i3-si|,...|in -si| An item from item Set with minimum difference Bestmatch = min|ii - si| can be chosen as best fit or maximum matched for further processing.

Figure 1.2 Overview of steganography.

1.2 Background History

The process of hiding secret information behind a carrier is called steganography. Steganography in a real sense is an old concept which was first implemented 3,000 years ago. In ancient times, people used this technique manually to transmit a message from one place to another place with the help of fly. They removed hair on the back neck of the fly and then a message was coded on the neck. They waited until hair regrew on the neck and then transmitted this message to its destination. Nowadays, steganography comes in entirely different forms, called as digital steganography, where digital data get concealed behind digital carrier object. The carrier object is maybe a picture, an audio or video. Different steganography techniques were introduced in the last 10 years that make data transmission more secure without inferring data by an intruder.

The first steganography techniques were called as Least Significant Bit substitution (LSB), where a secret information bit get concealed at first (from right to left) position of carrier sample. To understand this, let's consider a carrier sample in binary format (00010101) and secret bit is 0. After hiding secret bit 0, result carrier sample become (00010100). This technique is simple to implement and preserves the audio-visual perceptual quality of carrier. However, due its simplicity, an intruder may easily locate the secret bit position which may create the possibility of unauthorized data extraction.

The drawbacks of the least significant bit substitution technique were removed by hiding secret Bits in higher and higher LSB position. Moving from LSB to Most Significant Bit (MSB) increases quantization error Qe. Increasing Quantization error creates a difference between the result and original carrier object, due to which it is very easy for an intruder to locate the existence of secret information...