Evaluation of Effectiveness of Random Variations in Signal Levels Transformed for Data Hiding

Abstract

In a method of hiding data in bit-planes that correspond to a series of digital signals, a single bit is chosen from the bits of each processed signal and then inverted. In a previous work a level transformation that performs the following three functions has been proposed: inverting the chosen bit, minimizing the level change caused by the bit inversion, and yielding random variations in the output level. This paper evaluates the random variations resulting from the transformation and demonstrates its effectiveness in secure data hiding.First, the properties of the level transformation are analyzed. Some theoretical values are also calculated especially to evaluate the increase of level differences caused by the random variations. Next, results of computer simulations of the transformation are presented, and the changes in level distributions are measured. These results indicate that the random variations in output levels reduce effectively the deformation of the level distributions at the expense of a little increase of the level differences.

Measurement of subjective quality of watermarked images made by inverting bits

“…In our previous paper [3], we presented a level transformation that performs both the inverting of a chosen bit and the minimizing of level change caused by the inverted bit. Next, a stochastic process was added to the transformation to make some bits of the transformed values random [4], [5]. Furthermore, in the preceding papers [6], [7], we have modified the level transformation by replacing the coordinate system by that based on the shifting and modular arithmetic to improve the properties over the whole dynamic range.…”