Data hiding in still images

We discuss the various techniques for data hiding in still images:

• LSB insertion [JJ98-1]
• spread spectrum [MBR98]
• texture block [Ben96]
• patchwork [Ben96] [GB98]
• Orthogonal projection coefficients manipulation [WW98] [FBS98]
• other methods: dithering manipulation, perceptual masking, DCT coefficients manipulation. [MBR98]

To remain invisible to the eye, these techniques must exploit "holes" in the Human Visual System (HVS):

• the masking effect of edges
• the varying sensitivity to contrast as a function of spatial frequency
• the low sensitivity to small changes in luminance for random patterns
• the low sensitivity to very low spatial frequencies, such as continuous changes in brightness through an image.

An advantage in using still images for data hiding is that they represent a noncausal medium, since it is possible to access any pixel of the image at random.

References:

• [FBS98]
• [WW98]
• [MBR98]
• [JJ98-1]
• [Ben96]
• [GB98]

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