Existing methods for reversible data hiding in ciphertext binary images only involve one data hider to perform data embedding. When the data hider is attacked, the original binary image cannot be perfectly reconstructed. To this end, this letter proposes multi-party reversible data hiding in ciphertext binary images, where multiple data hiders are involved in data embedding. In this solution, we use visual cryptography technology to encrypt a binary image into multiple ciphertext binary images, and transmit the ciphertext binary images to different data hiders. Each data hider can embed data into a ciphertext binary image and generate a marked ciphertext binary image. The original binary image is perfectly reconstructed by collecting a portion of marked ciphertext binary images from the unattacked data hiders. Compared with existing solutions, the proposed solution enhances the recoverability of the original binary image. Besides, the proposed solution maintains a stable embedding capacity for different categories of images.

In this article, a secret image sharing (SIS) scheme for general access structures (GAS) is designed for distributed multi-user scenario. In the proposed distributed multi-user SIS (DM-SIS), multiple secret images are encoded into shadows which are then distributed to the corresponding storage nodes of a network. By collecting the shadows from nodes, each user is capable of decrypting the corresponding secret image. Fundamentally, we utilize an invertible target matrix, which is initially obtained from the GAS and a base matrix with Vandermonte coordinates, to construct shadows. To deal with the case of non-invertible target matrix, three matrix-adjusting procedures are further introduced. Theoretical analysis, numerical examples, and experiments are provided to verify the feasibility of the proposed technique. When compared to previous methods, the proposed approach can implement GAS sharing strategy in distributed multi-user environment. Meantime, significant improvements on storage overhead and sharing capacity are also achieved.

A systematic investigation of evolving visual cryptography scheme (EVCS) is carried out in this article. The evolving scheme, denoted as \((k,\infty)\) , differs from the \((k,n)\) threshold in that it permits an arbitrary and perhaps unlimited number of participants. More importantly, the access structure can be updated dynamically by adding new users. First of all, a preliminary implementation strategy for the \((2,\infty)\) EVCS is introduced. Then, by employing the \((2,2)\) VCS recursively with the \((2,\infty)\) EVCS, a \((k,\infty)\) EVCS is created. In order to enhance the performance, an improved scheme is constructed based on the multi-secret VCS (MVCS) and a series of EVCS schemes with thresholds of \((1,\infty)\) , \(\cdots\) , \((k-1,\infty)\) . Moreover, Boolean XOR operation is adopted for secret recovery to further improve the visual quality. To facilitate the XOR decryption, a novel access structure partition algorithm is presented. Additionally, the proposed partition method can successfully solve the security issue in existing multi-secret XOR-based VCS (MXVCS). By integrating the more secure MXVCS into the improved scheme, XOR decryption is provided. The two proposed methods are shown to be effective and advantageous through extensive experiments and comparisons.

The risk of malicious exploitation of advanced image steganography necessitates the removal of hidden information from images. However, it is crucial to preserve the visual quality of the images undergoing processed. This paper suggests a geometrical attack in frequency domain (GAF) to address this challenge. GAF employs a thin plate spline (TPS) to slightly geometrically perturb the frequency components of the stego image. It incorporates a channel weight estimator and a frequency jammer. The channel weight estimator assigns perturbation strengths to each DCT channel, while the frequency jammer performs the TPS transform on the DCT channels using the assigned perturbation strengths. Experimental results demonstrate that the proposed approach effectively hinders secret image recovery with a little distortion to the stego images. Furthermore, it well preserves the visual quality of clear images that do not contain secret information.

The existing models of reversible data hiding in encrypted images (RDH-EI) are based on single data-hider, where the original image cannot be reconstructed when the data-hider is damaged. To address this issue, this article proposes a novel model with multiple data-hiders for RDH-EI based on secret sharing. It divides the original image into multiple different encrypted images with the same size of the original image and distributes them to multiple different data-hiders for data hiding. Each data-hider can independently embed data into the encrypted image to obtain the corresponding marked encrypted image. The original image can be losslessly recovered by collecting sufficient marked encrypted images from undamaged data-hiders when individual data-hiders are subjected to potential damage. This further protects the security of the original image. We provide four cases of the proposed model, namely, two joint cases and two separable cases. From the proposed model, we derive a separable RDH-EI method with high-capacity. Experimental results are presented to illustrate the effectiveness of the proposed method.