High capacity data hiding based on multi-directional pixel value differencing and decreased difference expansion

Data hiding is an important research topic over the years. The PVD based techniques embed secret data into the cover image on the difference between the two neighboring pixels. Most of the PVD based techniques are unidirectional that signifies less embedding capacity. The embedding capacity of the PVD technique is utilized in this article to embed the data in multi-directions. To improve the embedding capacity, a new high capacity data hiding technique based on decreased difference expansion (DDE) method and the multidirectional pixel value differencing (MPVD) is proposed. It is based on the block embedding technique for embedding data in the non-sequential locations. The cover image is divided into 2 x 2 non-overlapping blocks. A basic pixel is selected and data hiding takes place in three pixel pairs containing the basic pixel. Distortion due to message embedding is high in the difference expansion (DE) based data hiding techniques. DDE method improves the DE method by reducing the difference between two pixels with a logarithm function and hence increases the quality of the images compared to the DE method. The proposed technique achieves an average embedding capacity of 2.88 bpp which is higher than several recent state-of-the-art works. It withstands the tests of StirMark Benchmark 4.0, and the steganalysis attacks.