Abstract
Steganography is the technique which has been used in many fields for hiding information and many different versions for each application are available in the literature. This chapter demonstrates how to increase the security level and to improve the storage capacity of hidden data, with compression techniques. The security level is increased by randomly distributing the text message over the entire image instead of clustering within specific image portions. The degradation of the images can be minimized by changing only one least significant bit per color channel for hiding the message. Using steganography alone with simple LSB has a potential problem that the secret message is easily detectable from the histogram analysis method. To improve the security as well as the image embedding capacity indirectly, a compression based scheme is introduced. Various tests have been done to check the storage capacity and message distribution.
TopTraditional and novel techniques for addressing the data-hiding process and evaluated these techniques with various perspectives are discussed in (Bender, 1996). A state of the art can be seen in (Rabah, 2004; Kipper, 2005). The theoretical model of steganography with respect to images as digital medium is well discussed in (Johnson, 1998; Eggers, 2002; Cachin, 1998). We preferred using images over audio files as they lack in embedding capacity, which is one of the most important criteria for implementing steganography.
Key Terms in this Chapter
Random Distribution: This is a way to distribute a series or pattern or something in random way. This can be purely random or pseudo-random, so that it can be somehow predictable.
Resolution: The width and height of an image is counted in terms of pixels. The resolution is shown in terms of width*height, like 640*480.
Pixel: This is the smallest element in the image. Pixel is picture element. It may be circular or square. Its size depends on hardware.
Degradation: if the color quality of image as host signal OR any attribute of host signal changes after hiding another signal, this change in attribute quality deragrade host signal. This process is called degradation.
Host Signal: This is a signal which may be image, audio, video or something else, which would be used to hide a signal inside.
Steganography: This is an area where a signal (any kind of data) can be inserted into host signal (generally Image) to hide. Only host signal is visible after the process.