# Reversible Data Hiding in Encrypted Images Based on the Mixed Multi-Bit Layer Embedding Strategy
## 5 Conclusions  
This paper focuses on improving embedding capacity and recovery performance in encrypted images and proposes a separate RDH-EI scheme. The scheme can achieve complete error-free extraction of secret data, high decryption of the cover image, and realize lossless recovery of the cover image with auxiliary data. It is mainly supported by the following four points. (1) The scheme divides the cover image into blocks of different types through two-round processing, maximizing the embeddable space as much as possible. (2) The mixed embedding strategy adopts different methods for blocks of different types, further increasing the pure capacity and hiding more secret data. (3) the spatial correlation of the original image is utilized to improve the quality of the directly decrypted image and obtain a high-quality decrypted image. (4) The auxiliary data help the receiver to achieve separable data extraction and increase the flexibility of the scheme.  
Compared to the state of-the-art works, the proposed scheme is superior in terms of embedding capacity, decryption quality, and separability. It can be applied in data privacy protection, data hiding, efficient transmission, and other scenarios. In further study, the research focus will be on that how to reduce auxiliary data and improve the embedding capacity to realize the transmission of secret data more efficiently and safely.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Schemes** & **Separability** & **Error in the Extracted Data** & **Error in the Recovered Image** & **Reserving Room** \\ \hline [PERSON] [14] & No & Yes & Yes & No \\ [PERSON] et al. [15] & No & Yes & Yes & No \\ [PERSON] et al. [16] & No & Yes & Yes & No \\ [PERSON] [17] & Yes & No & Yes & No \\ [PERSON] [18] & Yes & No & No & No \\ [PERSON] et al. [19] & Yes & No & No & No \\ [PERSON] et al. [20] & Yes & No & No & No \\ [PERSON] et al. [22] & Yes & No & No & No \\ [PERSON] et al. [23] & Yes & No & No & Yes \\ [PERSON] et al. [24] & Yes & No & No & Yes \\ [PERSON] et al. [25] & Yes & No & No & Yes \\ [PERSON] et al. [30] & No & No & No & Yes \\ [PERSON] et al. [34] & Yes & No & No & Yes \\ [PERSON] et al. [41] & No & No & No & No \\ Proposed & Yes & No & No & Yes \\ \hline \hline \end{tabular}
\end{table}
Table 5: Comparison of other metrics.  
**Author Contributions:** Conceptualization, resources, writing--review and editing, supervision, project administration and funding acquisition, are provided by Q.Z.; methodology, software, validation, formal analysis, investigation, data curation, writing--original draft preparation and visualization, are provided by R.-H.L. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the National State Key Laboratory Fund (6142411432107, 6142811204306, 61428411184406).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Data sharing is not applicable to this article as no new data were created or analyzed in this study.  
**Conflicts of Interest:** The authors declare no conflict of interest.