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As the number of people using the Internet has increased, more information is stored and accessible daily. As a result, the requirement for information security also grows. In the early stages of data security, cryptography is used. Cryptography turns readable information into an unreadable form. Steganography is the next generation of information security. The main downside of this steganography is that the digital media becomes damaged due to hiding information in digital media. The next stage of information security is Reversible Data Hiding (RDH). This method can restore personal information and digital media without error. The next method, Separable Reversible Data Hiding in Encrypted Digital Media, recovers the digital media and extracts concealed information independently without disturbing or knowing each other. This paper presents a novel Separable Reversible Data Hiding by Vacating Room After Encryption using the Encrypted Pixel Difference (SRDH-VRAE-EPD) method, which combines homomorphic encryption and encrypted pixel differences. The proposed method offers the following advantages. It achieves an embedding rate of 1.2 bpp, significantly improving upon standard VRAE algorithms while allowing for lossless data extraction and image recovery. The encrypted image ensures high security against various attacks, including statistical, differential, and chosen plaintext attacks, and it allows for the extraction of secret data and recovery of the original image independently, making it a separable process.

The volatile development in the multimedia cognitive content is changing the global set-up towards a cloud-based architecture which is helped us with a massive amount of computer storage and the highest computational platform. Cost-saving and elasticity of services will be provided by progressive cloud computing technology for users. With the advancement in multimedia technology, the data owners outsource their private multimedia data on the hybrid cloud. Meantime the cloud servers also carry out some highly computationally expensive tasks. Nevertheless, there is an opportunity for security infracts possible in the public cloud environment. It makes an alarm for a cloud environment in security aspects. Before outsourcing multimedia data, an encryption technique is needed for safeguarding against several attacks. But performing the same is a significant challenge. A new research area was recently awakened on privacy-preserving Reversible Data Hiding (RDH) especially for multimedia data over the outsourced environment. A novel RDH for an encrypted image was proposed in this paper by using the (Most Significant Bit) MSB difference of the pixel value. By using this method, any third-party people can embed the ciphertext in the cipher image without the knowledge of the cover and secret. A person with decryption keys can get back the secret and the cover without any loss. The proposed work achieves the embedding capacity up to 1 bpp (bits per pixel) with the encryption quality of near-zero correlation and uniform histogram. The decrypted image is also retrieved with infinite Peak Signal to Noise Ratio (PSNR), unit Structural Similarity Index Metric (SSIM) and zero Bit Error Rate (BER).

A reversible data hiding in the encrypted domain (RDH-ED) aims to hide data within encrypted images, protecting its content, while allowing additional information to be distributed. This paper presents a complete separable RDH-ED scheme, whose main contribution is allowing the receiver to extract data and restore the image, either from the cryptogram with hidden data or from the directly decrypted version. With versatile bit-depth management, the most significant bits of each pixel are encrypted with AES-CTR cipher algorithm, while the additional data will be inserted inside the least significant bit planes of the encrypted pixels, by means of the code division multiplexing technique. Considering the marked/encrypted images, and encryption/data-hiding keys, a receiver could: (a) directly decrypt the encrypted image and obtain its approximate version, (b) extract the error-free hidden data, and (c) recover the data and original image. Considering an image approximation version and the data hiding key, a receiver could: (d) extract the hidden data from the plaintext domain, and (e) restore the image to its original state, while accessing the hidden data without any loss. Experimental results show the performance of the developed algorithm, evaluating the capacity and imperceptibility of the proposed scheme with respect to current state of the art.

E-healthcare requires communication of patient report to a specialized doctor in a real time scenario. Therefore, any harm to patient medical data can lead to a faulty diagnosis that can be lethal for the patient. To ensure safe and secure communication in E-healthcare framework, a high capacity dual image separable reversible data hiding algorithm in the encrypted domain has been presented in this paper. All compared reversible data hiding techniques have been shown predominant outcomes, yet just on natural images not on medical images because underflow problem may arise in medical images due to a large number of pixels have low-intensity values. Thus, an enhanced separable reversible data hiding technique in the encrypted domain has been introduced here that gives a higher embedding rate than all the looked at reversible data hiding techniques by embedding l o g 2 ( u - l + 1 ) binary bits of patient information at non-seed pixels of the cover image without any occurrence of underflow and overflow problem so that empowering it to embed and recover information precisely from low-intensity pixels too. This property makes our proposed methodology truly reasonable for its utilization on medical images. For authentication analysis of electronic patient information (EPI) at the recipient end, a fragile watermark has also been embedded with EPI respectively. For all test images, embedding rate of 2.38 bits per pixel (bpp) with an average PSNR value is 41.05 dB is observed which demonstrates that the proposed method is capable of giving good quality stego images even at high payload also.

In the telemedicine industry, a standout among the most significant issue is the exchange of Electronic Patient Information (EPI) between patient and a doctor that are remotely connected. A minute change to EPI may result in a wrong diagnosis for the patient. To ensure secure and safe communication for telemedicine applications, a dual-image separable block-based reversible data hiding algorithm in encrypted domain for embedding secret message in base5 numeral framework is proposed here. The proposed scheme has not been suffering from underflow and overflow problem so that empowering it to embed and recover information precisely from low-intensity pixels too. This property makes our proposed methodology truly reasonable for its utilization on medical images. To prove the effectiveness of our proposed approach, experiments have been performed on different test images. The average PSNR value is 54.10 dB for an embedding capacity of 327,680 bits for all test images which demonstrates that the method is capable of giving good quality stego images even at high payload also. The experimental study revealed that for all types of test images, the proposed methodology altogether beaten all the compared methodologies in its ability to embed secret message and precisely recover it by maintaining the visual quality of stego images too.

We propose separable reversible data hiding in an encrypted signal with public key cryptography. In our separable framework, the image owner encrypts the original image by using a public key. On receipt of the encrypted signal, the data-hider embeds data in it by using a data-hiding key. The image decryption and data extraction are independent and separable at the receiver side. Even though the receiver, who has only the data-hiding key, does not learn about the decrypted content, he can extract data from the received marked encrypted signal. However, the receiver who has only the private key cannot extract the embedded data, but he can directly decrypt the received marked encrypted signal to obtain the original image without any error. Compared with other schemes using a cipher stream to encrypt the image, the proposed scheme is more appropriate for cloud services without degrading the security level.

Separable Reversible Data Hiding in Encryption Image (RDH-EI) has become widely used in clinical and military applications, social cloud and security surveillance in recent years, contributing significantly to preserving the privacy of digital images. Aiming to address the shortcomings of recent works that directed to achieve high embedding rate by compensating image quality, security, reversible and separable properties, we propose a two-tuples coding method by considering the intrinsic adjacent pixels characteristics of the carrier image, which have a high redundancy between high-order bits. Subsequently, we construct RDH-EI scheme by using high-order bits compression, low-order bits combination, vacancy filling, data embedding and pixel diffusion. Unlike the conventional RDH-EI practices, which have suffered from the deterioration of the original image while embedding additional data, the content owner in our scheme generates the embeddable space in advance, thus lessening the risk of image destruction on the data hider side. The experimental results indicate the effectiveness of our scheme. A ratio of 28.91% effectively compressed the carrier images, and the embedding rate increased to 1.753 bpp with a higher image quality, measured in the PSNR of 45.76 dB.

Considering the applications of requiring high fidelity of multimedia content, and for the purpose of copyright protection, a separable and dual data hiding algorithm is proposed. In this paper, the definitions of Ternary Segmentation (TS), Hidden Pixel Pair (HPP), ZN-shape space-filling curve, and Lucas-Arnold Scrambling (LAS) are presented for the first time. By virtue of without degrading the quality of the host image, this paper combines reversible data hiding and zero data hiding to solves the contradiction between robustness and imperceptibility. Firstly, 1-level reversible data hiding is performed using TS, HPP and Huffman compression. Then, 2-level zero data hiding is adopted based on LAS, IWT (Integer Wavelet Transform), BN-SVD(Boost Normed Singular Value Decomposition) and ZN-shape space-filling curve. Finally, separable decryption and extraction is conducted. The experiment results prove that the proposed scheme achieves a better image perceptual quality with an average PSNR of about 49 dB, and stronger robustness with an average NCC of about 0.99 under various attacks. Moreover, it achieves higher security, and the average values of information entropy, correlation coefficient, NPCR and UACI are 7.9, 0.01, 99.6854% and 33.4378%, respectively.

To better protect the security of users’ private data in the cloud environment, the technology for separable reversible data hiding in encrypted images has been attracting increasing attention from researchers. In this paper, we propose a separable reversible data hiding scheme in encrypted images based on the flexible preservation of differences. This scheme has three parts: 1) For the content owner, the original image is divided into non-overlapping blocks, for which block-mean is computed. Then the differences between the values of every pixel and the block-mean are obtained and an initial label map is generated. Because most of the differences tend to concentrate around 0, we use two bits to dynamically record the range of the differences to vacate space for hiding. Further, introducing the block-mean differences also serves to vacate more space, for which the label map is amended accordingly. Finally, the image with free space is encrypted into the encrypted image using an encryption key. 2) For the data hider, the secret bits are embedded into the encrypted image by directly replacing the spare bits without obtaining any information of the original image. 3) For the receiver, he/she can achieve the desired information according to the key in his/her possession. Experimental results show that our proposed scheme is able to achieve an average embedding capacity as large as 1.785 bpp and 1.709 bpp when block size is set to 2 × 2 and 2 × 4, respectively. Comparison with those of previous schemes, the proposed scheme has excellent embedding capacity, especially for smoother images.

Data hiding is a field widely used in copyright, annotation, and secret communication for digital content, and has been continuously studied for more than 20 years. In general, data hiding uses the original image as a cover image to hide data, but recently, the research area has expanded to research on improving the security and privacy protection of image contents by encrypting the image. This research is called separable reversible data hiding in an encrypted image (SRDH-EI). In this paper, we proposed a more efficient SRDH-EI method based on AMBTC. AMBTC can guarantee very good network transmission efficiency for applications that do not require a particularly high image quality because the compression time is short and calculation is simple compared to other existing compression methods. The SRDH-EI method presented here divides AMBTC into non-overlapping 4×4 blocks and then performs image encryption on them. Thereafter, data can be hidden using a Hamming code for each block. The proposed method has an advantage in that the quality of the cover image and the hiding capacity can be adjusted by appropriately using the value T of the difference between the two quantization levels. The experimental results proved the efficiency and superiority of our proposed model.