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This paper proposes a fully homomorphic encryption encapsulated difference expansion (FHEE-DE) scheme for reversible data hiding in encrypted domain (RDH-ED). The homomorphic circuits and ciphertext operations are elaborated. Key-switching and bootstrapping techniques are introduced to control the ciphertext extension and decryption failure of homomorphic encryption. A key-switching based least-significant-bit (KS-LSB) data hiding method has been designed to realize data extraction directly from the encrypted domain without the private key. In application, the user first encrypts the plaintext and uploads ciphertext to the server. The server embeds additional data into the ciphertext by performing FHEE-DE data hiding and KS-LSB data hiding. Additional data can be extracted directly from the marked ciphertext by the server without the private key. The user owns the private key and can decrypt the marked ciphertext to obtain the marked plaintext. Then additional data or plaintext can be obtained from the marked plaintext by using the standard DE extraction or recovery. The server could also implement FHEE-DE recovery or extraction on the marked ciphertext to return the ciphertext of original plaintext or additional data to the user. Experimental results demonstrate that the embedding capacity and reversibility of the proposed scheme are superior to existing RDH-ED methods, and fully separability is achieved without reducing the security of encryption. [ABSTRACT FROM AUTHOR]

This paper proposes a multilevel reversible data hiding scheme in encrypted domain by utilizing the controllable redundancy of learning with error public key cryptography. Messages can be embedded into multilevel sub-regions of ciphertext by quantifying the encrypted domain and recoding its redundancy. We recode redundancy based on the characteristics of cipher’s distribution. Extraction and decryption processes are separated by dividing the encrypted domain into multilevel sub-regions and introducing different quantification standards. Original plaintext can be losslessly recovered from the marked ciphertext by using the decryption key; with a specific level data-hiding key, only the message hiding in the corresponding level can be extracted, while plaintext and other messages remain secret. We provide theoretical analysis and experimental results on the feasibility, reversibility, and security of the proposed scheme. The capacity and encryption blow up factor are discussed. The experimental results demonstrate the maximum embedding rate can exceed 0.3000 bpb of ciphertext. [ABSTRACT FROM AUTHOR]