# Data Hiding and Authentication Scheme for Medical Images Using Double POB
## 1 Introduction  
With the swift growth of internet technology and network infrastructure, electronic medical care is also developing rapidly. Nowadays, medical data are mainly maintained electronically as electronic patient records (EPRs); EPR data include medical images, health record data, patient history, etc., that need to be transmitted. Medical images have highly strict image quality criteria because they are one of the most significant tools used by doctors to diagnose illness. Any small change may lead to an incorrect diagnosis or even serious medical accidents. To secure the confidentiality, dependability, and availability of medical images, many data-hiding algorithms and image encryption algorithms have been proposed. Furthermore, to prevent tampering with the integrity of encrypted images, image restoration algorithms have become a popular research topic. Data-hiding technology is often used to protect patients' privacy information in telemedicine applications. This technology refers to the process of attaching data information that needs to be transmitted to the carrier image. There are already many data-hiding algorithms based on medical images, [PERSON] et al. [1] introduced a hybrid image watermarking scheme based on the separation of ROI andRONI, and medical data and least significant bits (LSBs) data from the ROI were attached to theRONI. A high-volume steganography algorithm based on medical images was proposed by [PERSON] et al. [2]. [PERSON] et al. [3] introduced a robust telemedicine application watermarking technology that includes singular value decomposition and combines Discrete Wavelet Transformation(DWT) and Discrete Cosine Transform (DCT) transforms. A new adaptive reversible watermarking scheme applied to medical images was proposed by [PERSON] [4]; the algorithm extends the estimation error of adjacent pixels to embed the watermark and can automatically segment the target region and background region of a medical image. Although the visual and embedding quality of the image can be guaranteed by data-hiding techniques, privacy protection requirements may not be satisfied by simply embedding the hidden data into the original image. Therefore, reversible data hiding in encrypted images (RDHEI) technology has emerged as a prospective method. [PERSON] et al. [5] separated the encrypted image into blocks to make room for hiding secret messages by compressing the difference between pixels. [PERSON] and [PERSON] [6] proposed a scheme to compress the block using the uniform most significant bit (MSB) of the pixels in the block, which achieved good results, but this scheme is not suitable for complex images. [PERSON] et al. [7] determined the embeddable block by analyzing the position of the MSB layer in the encrypted image. To make space for embedding data, the MSB layer of the embeddable block needs to be compressed in an adaptive way. In order to preserve the redundancy in the encryption block, [PERSON] et al. [8] adopted the classical XOR method to encrypt the block and used the redundancy matrix existing in the encrypted block to generate the available space that could accommodate the secret message. [PERSON] [9] split the image through blocks for encryption and compressed it using the data hider to free up space for embedding the encrypted secret message. To guarantee the quality of the decrypted image, [PERSON] et al. [10] separated the image into a texture block and a smooth block, and they just inserted additional data into the smooth block. Nowadays, most block-based RDHEI schemes deal with data hiding and encryption separately. As a result, it is required and critical to investigate a method for synchronizing data embedding and encryption in order to reduce the threats of potentially insecure encryption systems. RDHEI technology can only ensure the safety of medical images; it cannot guarantee the dependability and availability of medical images. Therefore, in the field of integrity and authentication of medical images, [PERSON] et al.