What is Image Steganography in Information Security?

Images are the most famous cover objects used for steganography. In image steganography, pixel intensities are used to conceal the information. In the area of digital images, there are different image file formats exist, most of them for definite applications.

An image is a set of numbers that constitute different light intensities in different location of the image. This numeric description forms a grid and the single points are defined as pixels. Most images on the Internet includes a rectangular map of the image’s pixels (defined as bits) where each pixel is situated and its colour. These pixels are shown horizontally row by row.

The number of bits in a colour design, known as the bit depth. It can define the number of bits used for each pixel. The smallest bit depth in modern colour design is 8, defining that there are 8 bits used to define the colour of each pixel.

Monochrome and greyscale images need 8 bits for every pixel and are capable to display 256 multiple colours or shades of grey. Digital colour images are generally saved in 24-bit files and need the RGB colour model, also called a true colour.

All colour modification for the pixels of a 24-bit image are changed from three primary colours such as red, green and blue, and each primary colour is defined by 8 bits.

Therefore in one given pixel, there can be 256 multiple quantities of red, green and blue, inserting up to more than 16-million set, resulting in higher than 16-million colours.

When working with bigger images of higher bit depth, the images influence to become too large to send over a standard web connection. It can show an image in a reasonable amount of time, techniques should be incorporated to decrease the image’s file size.

These techniques create use of numerical formulas to evaluate and condense image data, resulting in smaller document sizes. This process is known as compression.

In images there are two types of compression including lossy and lossless. Both methods save storage areas, but the processes that they execute differ.

Lossy compression generates smaller document by discarding excess image data from the initial image. It can eliminate details that are too small for the human eye to understand, resulting in close approximations of the original image, although not a correct matching.

Lossless compression never eliminates any data from the original image, but instead defines data in numerical formulas. The initial image’s integrity is supported and the decompressed image output is bit-by-bit equal to the initial image input.

Compression plays an essential role in selecting which steganographic algorithm to use. Lossy compression techniques result in smaller image document sizes, but it enhance the possibility that the installed message can be partly lost because of the fact that excess image data will be eliminated.

Lossless compression maintain the initial digital image intact without the chance of lost, although it does not restrict the image to such a small document size.