Vasiliy Sachnev

Reversible Watermarking Algorithm Using Sorting and Prediction

This paper presents a reversible or lossless watermarking algorithm for images without using a location map in most cases. This algorithm employs prediction errors to embed data into an image. A sorting technique is used to record the prediction errors based on magnitude of its local variance. Using sorted prediction errors and, if needed, though rarely, a reduced size location map allows us to embed more data into the image with less distortion. The performance of the proposed reversible watermarking scheme is evaluated using different images and compared with four methods: those of Kamstra and Heijmans, Thodi and Rodriguez, and Lee et al. The results clearly indicate that the proposed scheme can embed more data with less distortion.

A Novel Difference Expansion Transform for Reversible Data Embedding

Reversible data embedding theory has marked a new epoch for data hiding and information security. Being reversible, the original data and the embedded data should be completely restored. Difference expansion transform is a remarkable breakthrough in reversible data-hiding schemes. The difference expansion method achieves high embedding capacity and keeps distortion low. This paper shows that the difference expansion method with the simplified location map and new expandability can achieve more embedding capacity while keeping the distortion at the same level as the original expansion method. Performance of the proposed scheme in this paper is shown to be better than the original difference expansion scheme by Tian and its improved version by Kamstra and Heijmans. This improvement can be possible by exploiting the quasi-Laplace distribution of the difference values.

Less detectable JPEG steganography method based on heuristic optimization and BCH syndrome coding

This paper presents an efficient JPEG steganography method based on heuristic optimization and BCH syndrome coding. The proposed heuristic optimization technique significantly decreases total distortion by inserting and removing AC coefficients 1 or -1 in the most appropriate positions. The implemented data hiding technique is based on structured BCH syndrome coding. This method achieves multiple solutions for hiding data to a block of coefficients. The proposed data hiding method chooses the best solution with minimum distortion effect. As a result, the total distortion can be significantly reduced, which results in less detectability of the steganalysis. The experiments include the steganalysis of the proposed data hiding methods. The experiment results shows that the proposed heuristic optimization significantly decreases detectability of the steganalysis. The proposed methods also outperform the existing steganography methods.

Fast BCH Syndrome Coding for Steganography

This paper presents an improved data hiding technique based on BCH (n,k,t) syndrome coding. The proposed data hiding method embeds data to a block of input data (for example, image pixels, wavelet or DCT coefficients, etc.) by modifying some coefficients in a block in order to null the syndrome of the BCH coding. The proposed data hiding method can hide the same amount of data with less computational time compared to the existed methods. Contributions of this paper include the reduction of both time complexity and storage complexity as well. Storage complexity is linear while that of other methods are exponential. Time complexity of our method is almost negligible and constant for any n. On the other hand, time complexity of the existing methods is exponential. Since the time complexity is constant and storage complexity is linear, it is easy to extend this method to a large n which allows us to hide data with small embedding capacity. Note that small capacities are highly recommended for steganography to survive steganalysis. The proposed scheme shows that BCH syndrome coding for data hiding is now practical ascribed to the reduced complexity.

An Efficient Embedder for BCH Coding for Steganography

This paper presents an improved data hiding technique based on BCH (n,k,t ) coding. The proposed embedder hides data into a block of input data by modifying some coefficients in the block in order to null the syndrome. The proposed embedder can hide data with less computational time and less storage capacity compared to the existing methods. The complexity of the proposed method is linear while that of other methods are exponential for any block size n. Thus, it is easy to extend this method to a large n. The BCH syndrome coding for steganography is now viable ascribed to the reduced complexity and its simplicity of the proposed embedder.

An Innocuous Visual Cryptography Scheme

An innocuous visual secret sharing scheme over natural images is presented in this paper. Secret sharing scheme allows a group of participants to share a secret (i.e., an image) among them. In case of(k, n) visual cryptography any group of k qualified participants among n (where k les n) can reconstruct the secret. This paper presents (n, n) visual cryptography scheme. This scheme does not apply dithering techniques to hide a secret image. Thus, it does not degrade quality of the secret image and in particular, this scheme is far from negative photo effect. Instead of dithering, this scheme spreads data by applying simple arithmetic operations. The rationale of arithmetic operations is presented.

Modified BCH data hiding scheme for JPEG steganography

In this article, a new Bose-Chaudhuri-Hochquenghem (BCH)-based data hiding scheme for JPEG steganography is presented. Traditional data hiding approaches hide data into each block, where all the blocks are not overlapping each other. However, in the proposed method, two consecutive blocks can be overlapped to form a combined block which is larger than a single block, but smaller than two consecutive nonoverlapping blocks in size. In order to embed more amounts of data into the combined block than a single block, the BCH-based data hiding scheme has to be redesigned. In this article, we propose a way to get a joint solution for hiding data into two blocks with intersected coefficients such that any modification of the intersected area does not affect the data hiding process into both blocks. Due to hiding more amounts of data into the intersected area, embedding capacity is increased. On the other hand, the nonzero DCT coefficient stream is modified to achieve better steganalysis and to reduce the distortion impact after data hiding. This approach carefully inserts or removes 1 or -1 coefficients into or from the DCT coefficient stream according to the rule proposed in this article. Experimental results show that the proposed algorithms work well and their performance is significant.

A Novel Approach for JPEG Steganography

In this paper we present a novel steganography method for JPEG images. The proposed data hiding technique bases on removing and inserting AC coefficients 1 or -1. The candidates for removing and inserting are searched among all non rounded AC coefficients after quantization. The proposed search technique flags the most appropriate coefficients, which provide less degradation after modification. The proposed data hiding technique based on the modification the flagged coefficients significantly decreases distortion after data hiding and, as result, shows the less detectability for steganalysis. The proposed method was tested with steganalysis method proposed by T. Pevny and J.Fridrich. The experimental results show that the proposed method has less detectability compared to the existed widely used steganography methods as F5 and OutGuess.

Reversible watermarking algorithm with distortion compensation

A novel reversible watermarking algorithm with two-stage data hiding strategy is presented in this paper. The core idea is two-stage data hiding (i.e., hiding data twice in a pixel of a cell), where the distortion after the first stage of embedding can be rarely removed, mostly reduced, or hardly increased after the second stage. Note that even the increased distortion is smaller compared to that of other methods under the same conditions. For this purpose, we compute lower and upper bounds from ordered neighboring pixels. In the first stage, the difference value between a pixel and its corresponding lower bound is used to hide one bit. The distortion can be removed, reduced, or increased by hiding another bit of data by using a difference value between the upper bound and the modified pixel. For the purpose of controlling capacity and reducing distortion, we determine appropriate threshold values. Finally, we present an algorithm to handle overflow/underflow problems designed specifically for two-stage embedding. Experimental study is carried out using several images, and the results are compared with well-known methods in the literature. The results clearly highlight that the proposed algorithm can hide more data with less distortion.

Ternary data hiding technique for JPEG steganography

In this paper we present JPEG steganography method based on hiding data to the stream of ternary coefficients. In the proposed method each nonzero DCT coefficient is converted to the corresponding ternary coefficient. The block of 3m - 1 ternary coefficients is used for hiding m ternary messages by modifying one or two coefficients. Due to higher information density of the ternary coefficients, the proposed method has many solutions for hiding necessary data. Such a big choice enables to choose coefficients with lowest distortion impact. As a result, the proposed methods have better data hiding performance compared to the existing steganographic methods based on hiding data to stream of binary coefficients like matrix encoding (F5) and modified matrix encoding (MME). The proposed methods were tested with steganalysis method proposed by T. Pevny and J. Fridrich. The experimental results show that the proposed method has less detectability compared to MME (modified matrix encoding).