Towards Improving the Imperceptibility of Steganography Schemes: Adaptive Scaling Approach

摘要

A common practice of several steganography schemes is to replace the insignificant Discrete Cosine Transform (DCT) coefficients with the secret data. Scaling is an important step in image-based steganography schemes where secret image data is scaled down to blend closely to small high frequency DCT coefficients of the cover image. Scaling affects the stego image quality. Previous work either improved stego quality at the cost of low capacity or improved capacity at the cost of low stego quality. The proposed technique uses fixed block segmentation to create several unique homogeneous regions. The homogeneous regions on secret image are mapped on to the corresponding hiding area of high frequency DCT coefficients of cover image. Each homogeneous region of secret data has a corresponding single scale. The scaling factor value for each region is determined by finding a single value of the corresponding secret homogeneous regions and DCT coefficient in the cover using mean scale. The proposed methodology gives better stego image quality while keeping high hiding capacity. Results compared with fixed scaling shows improvement of stego quality for high fixed hiding capacity.