Abstract: With the rapid development of information technologies,more and more multimedia data represented by images are repeatedly uploaded to the cloud for storage,resulting in a great waste of communication and storage overhead.In addition,the plaintext images are directly stored in the cloud,which brings about the problem of confidentiality breach.Even though ciphertext deduplication is an effective means to deal with these problems,the differentiated response actually creates a side channel for attackers,which makes the existence privacy of data in cloud storage at risk.At the same time,in order to achieve key transferring between data owners,a huge amount of extra overhead is required.Thus,this paper proposes an efficient adaptive MSB reversible data hiding based secure deduplication(EMSD),which is able to effectively resist side channel attacks and save communication and storage overhead.Specifically,we innovatively introduce the reversible data hiding for encrypted images into ciphertext deduplication,and embed the auxiliary information for key transferring into the encrypted images before sending to the cloud.Thus the extra communication and storage overhead for auxiliary information are successfully eliminated.Furthermore,we optimize the existing deduplication scheme to ensure that even if the image in deduplication request is not duplicate,extra ciphertext uploading is not needed,thus indistinguishable response is achieved.Security analysis and experimental results show that,the proposed scheme is able to resist side channel attack in a lightweight way comparing with existing schemes.

Key words: Cloud storage, Deduplication for encrypted images, Side channel attack, Adaptive MSB prediction, Data hiding