Research On Reversible Data Hiding In Encryption Domain Without Preprocessing

In the 21 st century,Internet applications such as online photo albums,cloud disk,cloud servers have been widely used.Meanwhile,the privacy disclosure could be caused by the theft of private multimedia files when user's private multimedia files are transmitted without encryption.Thus,the private multimedia data need to be encrypted before transmission and storage.For the convenience of management,some extra data such as user information,classification information,etc.,can be reversible embedded into the encrypted multimedia files by the cloud server administrators.Hence,researchers have begun to specialize reversible data hiding(RDH)in the encryption domain.In most of the framework in that fields,the images need to be preprocessed before been encrypted to empty out room by using the RDH method.After that,extra data can be embedded into the reserved room of the encrypted image.But preprocessing brings inconvenience to the image owner and makes homomorphic processing in encrypted images impossible.To solve these problems,two schemes of reversible data hiding in the encryption domain without preprocessing is proposed in this thesis.Without preprocessing,image owner can encrypt images directly,and extra data can be embedded in the encrypted image.Part of the hidden data may be extracted before image decryption while the rest can be extracted after image decryption.1.A RDH method for homomorphic encrypted images without preprocessing is proposed.Image is encrypted using Paillier cryptosystem without any preprocess.The two-stage data hiding process in the encrypted image utilizing the value expansion and self-blinding algorithm.Moreover,the homomorphic processing can be performed before data embedding.Part of the hidden data may be extracted before image decryption while the rest can be extracted after image decryption.The experimental results on test images validate that the higher embedding capacity can be obtained with the proposed method compared with the state-of-the-art methods.2.Another RDH method for homomorphic encrypted images based on NTRU encryption system without preprocessing is proposed.Extra data is embedded into the encrypted image twice.Part of the hidden data may be extracted before image decryption while the rest can be extracted after image decryption.The experiments show that the execution time of data embedding is reduced greatly,and the maximum embedding rate in the encryption domain is the highest compared with the state-of-the-art methods.