Adaptive Steganography Method Based on Two Tiers Pixel Value Differencing

The pixel value differencing (PVD) scheme provided high embedding payload with imperceptibility in the stego images. In their approach, they used two pixels differencing to represent the complexity of pixels, and applied it to estimate how many bit will be hidden into. As the difference with small value, it means that two pixels can not tolerated with larger change, therefore, few secret bit should be embedded into these pixels. PVD scheme did not completely take pixel tolerance into consideration because of only applying one criterion, pixel differencing. In this paper, a new data hiding scheme using PVD operation and incorporating with pixel tolerance into a cover image is proposed. The pixel tolerance indicates that a greater pixel-value is more change of gray-value could be tolerated. Following up this idea, our proposed scheme applies a threshold (TH) and two quantization tables to hide secret data into a block with two pixels using modified k-bits LSB. The number of k-bits is adaptive and depends on the quantization tables setting. The adjustment strategy is to maintain the differencing value in the same range. The experimental results show that our scheme is superior to those in the previous literature.