Abstract: Reversible data hiding in encrypted domain is one kind of information hiding techniques which can both extract secret messages and decrypt the embedded ciphertext to restore the original cover vehicle losslessly, possessing privacy protection and data hiding dual function. It is a potential technique in signal processing and data management of the encrypted domain fields. This paper proposes a novel scheme of multiple bits reversible data hiding in encrypted domain based on R-LWE (ring-learning with errors). Multi-band data can be embedded by quantifying the encrypted domain and recoding in the redundancy of cipher text without degrading the hardness of R-LWE algorithm; the embedding recoding method is based on the data distribution during encryption, which maintains the robustness of R-LWE algorithm; By dividing the integer domain into the sub-regions and introducing different quantifying rules, the processes of extraction and decryption can be separated. By deducing the error probability of the scheme, parameters in the scheme which is directly related to the correctness of the scheme is mainly discussed, and reasonable ranges of the parameters are obtained by experiments. When analyzing the security, the probability distribution function of the embedded cipher text is deduced and the statistic features of cipher data are analyzed, which both prove the embedded data isn’t detective. Experimental results have demonstrated that the proposed scheme can not only keep fully reversibility of vehicle recovering and lossless extraction of secret message, but realize that one bit original data can load multiple-bit additional data in encrypted domain, achieving an embedding capacity of 0.2353 bit per every bit of the encrypted data.

Key words: information security, reversible data hiding, encrypted domain, multiple bits embedding, ring-learning with errors (R-LWE)