25-01-2013, 12:45 PM
Colour Guided Colour Image Steganography
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Abstract
Information security has become a cause of concern because of the electronic eavesdropping. Capacity, robustness and invisibility are important parameters in information hiding and are quite difficult to achieve in a single algorithm. This paper proposes a novel steganography technique for digital color image which achieves the purported targets. The professed methodology employs a complete random scheme for pixel selection and embedding of data. Of the three colour channels (Red, Green, Blue) in a given colour image, the least two significant bits of any one of the channels of the color image is used to channelize the embedding capacity of the remaining two channels. We have devised three approaches to achieve various levels of our desired targets. In the first approach, Red is the default guide but it results in localization of MSE in the remaining two channels, which makes it slightly vulnerable. In the second approach, user gets the liberty to select the guiding channel (Red, Green or Blue) to guide the remaining two channels. It will increase the robustness and imperceptibility of the embedded image however the MSE factor will still remain as a drawback. The third approach improves the performance factor as a cyclic methodology is employed and the guiding channel is selected in a cyclic fashion. This ensures the uniform distribution of MSE, which gives better robustness and imperceptibility along with enhanced embedding capacity.
INTRODUCTION
Communication skills have always been the hallmark of human interactivity. The primitive techniques that include cave drawings, smoke signal, drums etc. ascertain that over the years has been the modus operandi (mode of operation) of social & commercial intercourse. The technological proliferation in this electronic epoch has expanded horizons and has empowered organizations, nations or corporations to share intellectual information and be mutually benefitted by it. But with the rats race to acquire power, morals have devolved and has made electronic eavesdropping a prime problem. Any popular system of governance ranging from the banking sector to the administrative sector of a country must be behind the barrages of efficacious security systems to protect it from apathetic and amoral people who accomplice to pull out any valuable information they can grab. Data encryption [1] and Data hiding [2, 3] techniques are potential tools for securing sensitive information and hence is widely used to protect the data over an overt channel from malicious attackers.
RELATED WORKS
History provides us with a plethora of data hiding methods [2, 3, 7, 8, 9]. The first manifestation of steganography dates back to the Greeks. Herodotus passed information on wax covered tablets. Pirate legends tell of the practice of tattooing secret information, such as a map, on the head of someone, so that the hair would conceal it. Another common form is the use of invisible ink derived from vinegar, fruit juices and milk. In World War II, hidden sensors, microdot and grill methods were widely used. During civil war, there was a method of providing secret messages to slaves to aid their escape through quilt patterns. Presently watermarking [2] and spread spectrum techniques [2, 10] are gaining momentum.
THE PROPOSED METHODOLOGY
The proposed methodology uses the same principle of least significant bit insertion (LSB) along with a modified version of the Pixel Indicator method [18, 19]. Each pixel value of a colour image is represented by three bytes i.e. to define the intensity of the channels RED, BLUE, GREEN. One of the channels (RED, BLUE, GREEN) is used to indicate, how many numbers of binary data has to be hidden in the remaining two channels. Where in [18] authors proposed a Pixel Indicator methodology but the number of bits in each pixel is simple K bits LSB based steganography, which is not adaptive. In the stated methodology [19], the number of bits to be embedded in each channel is decided by Pixel value differencing (PVD) [17] and is also going to be guided by the indicator channel similar to [18]. The randomization, improved imperceptibility and robustness of the system are also simultaneously achieved by hiding the secret data in LSBs of the pixels [9], with more randomization in selection of the number of bits to be hidden and the channels in which the data is to be hidden [18]. The problem in [19] is moderate embedding capacity but it improves the imperceptibility with increased randomness.
Comparsion
Comparing the histograms of the RGB channels before and after the embedding, higher security performance was inferred. Interestingly, from different test runs we arrived at different distributions between the three channels which had no particular pattern in common. This varying pattern assured that this algorithm can be considered as pseudorandom, based on the randomness of the of the indicator channel.
CONCLUSION
In this paper we have proposed a novel and adaptive method to embed the secret data in the cover image with high security, imperceptibility and enhanced embedding capacity. The receiver does not need the original image to extract the information. The table presented is just a prototype and can be modified by the user to any desired level, which makes the method more flexible along with improved randomness. Moreover the embedding depends completely on the nature of the pixels which is not predictable. This makes it completely adaptive and random because the nature of the pixels cannot be controlled; it is inherent of an image. Our testing and results have shown that our method III performs better when compared to the methods I and II without giving any noticeable distortions.