Separable and error-free reversible data hiding in encrypted images

Digital image sometimes needs to be stored and processed in an encrypted format to maintain security and privacy, e.g., cloud storage and cloud computing. For the purpose of content notation and/or tampering detection, the cloud servers need to embed some additional information directly in these encrypted images. As an emerging technology, reversible data hiding in the encrypted domain will be useful in cloud computing due to its ability to preserve the confidentiality. In this paper, a novel separable and error-free reversible data hiding scheme in encrypted images is proposed. After analyzing the property of interpolation technology, a stream cipher is utilized to encrypt sample pixels and a specific encryption mode is designed to encrypt interpolation-error of non-sample pixels. Then, the data-hider, who does not know the original image content, may reversibly embed secret data into interpolation-error using a modified version of histogram shifting and difference expansion technique. In order to adapt to different application scenarios, data extraction can be done either in the encrypted domain or in the decrypted domain. In addition, real reversibility is realized, that is, data extraction and image recovery are free of any error. Experimental results demonstrate the feasibility and efficiency of the proposed scheme. Embedding is done on the encrypted image without knowing the decryption key.Two different encryption schemes are utilized to enhance the security.More flexible embedding mechanism is adopted for different capacity requirements.No errors occur in data extraction and image recovery.The hidden data can be extracted from the encrypted and/or decrypted image.