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Abstract To ensure the security of digital information, information needs to be stored and processed in the encryption domain during the cloud storage process, during which the user does not allow the cloud provider (CP) to access the image contents, and the CP must embed additional information in the image. Therefore, reversible data hiding in an encryption domain (RDHEI) has emerged. This paper presents an adaptive and separable multiary RDHEI method. First, the image is divided into two parts that consist of reference pixels and non-reference pixels. Next, we compute the prediction errors of the non-reference pixels, followed by a replacement of the original non-reference values with the computed prediction errors. Then, the entire image is encrypted with a specially designed stream cipher strategy so that the CP can embed additional information by modifying the prediction errors without knowing the original image. In addition, although our method vacates space before encryption, the CP can adaptively control the reserved space, unlike traditional RDHEI schemes which also vacate space before encryption. Because our method is separable, the embedded message can be extracted from both encryption and plaintext domains accurately. The experimental results demonstrate the efficacy of the proposed method.

For reversible data hiding in encrypted image (RDHEI), it is an important problem to resolve the contradiction between embedding capacity and image visual quality. However, existing schemes do not maintain a good balance between them. Accordingly, we propose a multi-level block selection embedding mechanism to solve this problem. Our scheme firstly divides original image into muliple non-overlapping blocks with identical size. The most significant bit (MSB) planes of all pixels in the block are predicted from their neighboring pixels to generate a corresponding prediction error map for each block. Subsequently, the pixels are divided into eight bit planes, and the adjacent bit planes are implemented XOR operation to vacate room. Furthermore, by simulating data embedding in each block, PSNR values of each image block are sequentially generated. After encrypting the image using stream ciphers, the optimal blocks with maximum PSNR value can be selected to embed data according to the secret data capacity. Since our proposed scheme usually selects the image block with maximum PSNR value to embed secret data, it can naturally improve the image visual quality. Extensive experiments demonstrate that our scheme is effective and efficient, and outperforms existing state-of-the art methods with better visual quality and higher security performance under the given embedding capacity. [ABSTRACT FROM AUTHOR]

Reversible data hiding in encrypted images (RDHEI), an essential branch of reversible data hiding (RDH), has been in development for more than a decade. For most existing stream-cipher-based RDHEI algorithms, encryption schemes are often not the same; thus, these schemes have different effects on the encrypted images. As a result, it is not reasonable to compare the embedding rates (ERs) of RDHEI algorithms directly as we do for plaintext RDH algorithms. However, to our knowledge, many studies focus on the performance of embedding but neglect the influence of the encryption. To compare the performance of stream-cipher-based RDHEI algorithms more reasonably, this paper proposes a novel comprehensive measure to evaluate state-of-the-art RDHEI algorithms. First, the characteristics of the stream-cipher-based RDHEI algorithms are divided into two categories according to the encryption and embedding processes. Next, we use correlation and redundancy to evaluate the influence of encryption schemes and also use ER, computation complexity, visual quality, and algorithm stability to evaluate the embedding schemes. In the end, in order to combine all six indexes into the final evaluation measure, we standardize each index before applying the radar chart. The experimental results show the evaluation results of the recent RDHEI algorithms via a comprehensive analysis and demonstrate the guiding significance of the proposed method for the current RDHEI algorithm selection. [ABSTRACT FROM AUTHOR]

To ensure the security of digital information, information needs to be stored and processed in the encryption domain during the cloud storage process, during which the user does not allow the cloud provider (CP) to access the image contents, and the CP must embed additional information in the image. Therefore, reversible data hiding in an encryption domain (RDHEI) has emerged. This paper presents an adaptive and separable multiary RDHEI method. First, the image is divided into two parts that consist of reference pixels and non-reference pixels. Next, we compute the prediction errors of the non-reference pixels, followed by a replacement of the original non-reference values with the computed prediction errors. Then, the entire image is encrypted with a specially designed stream cipher strategy so that the CP can embed additional information by modifying the prediction errors without knowing the original image. In addition, although our method vacates space before encryption, the CP can adaptively control the reserved space, unlike traditional RDHEI schemes which also vacate space before encryption. Because our method is separable, the embedded message can be extracted from both encryption and plaintext domains accurately. The experimental results demonstrate the efficacy of the proposed method. [ABSTRACT FROM AUTHOR]