Digital watermarking
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Inverting signal bits is a basic operation for data hiding such as digital watermarking. In the previous papers the level transformation that performs both inverting a specified bit and minimizing the resultant level change has been proposed. Because the transformation maps signal levels sparsely within the dynamic range, some variation of the transformed levels is necessary to conceal the fact that the signals are transformed. This paper proposes a method for varying the transformed levels randomly so that those bits that present the randomness can be distinguished. Then, these bits can represent a message to recover. Accordingly, a capacity of embedding additional bits increases. The performance of the proposed method is analyzed in a stochastic manner in terms of the resultant level distortion and an embedding capacity. A simulation result is also shown to demonstrate the actual performance in the application to digital images.