# A Watermark-Based In-Situ Access Control Model for Image Big Data
## 6 Conclusions  
In this paper, we propose a watermark-based access control model. In contrast to current access control methods, we attach access control strategies within accessed objects (e.g., images) as watermarks, instead of storing access control strategies on servers. Our proposed model makes it possible to let accessors view images without accessing servers. This can ease the burden of servers and shorten the access delay. In addition, our model also defends against several dedicated attacks for accessing big image data, such as transferring attack, DDoS attack, coarse access, and physical copy attack. Moreover, we also propose a hierarchical key-role-area access control model. In this model, multiple areas in an image can be mapped to one role, and each role is associated with a hierarchical key. Hierarchical keys are classified into levels and keys at higher security levels can derive keys at  
\begin{table}
\begin{tabular}{l c c c c c} \hline \hline
**Performance** & **Our Scheme** & **[PERSON] [7]** & **[PERSON] [9]** & **[PERSON] [10]** & **[PERSON] [11]** \\ \hline
1. Hierarchical access control & ✓ & ✗ & ✓ & ✗ & ✗ \\ \hline
2. Code access control & & & & & \\ strategies in watermarks & ✓ & ✗ & ✗ & ✗ & ✗ \\ \hline
3. Access control can take & & & & & \\ effect without servers & ✓ & ✗ & ✗ & ✗ & ✗ \\ \hline
4. Watermarks are used & & & & & \\ for access control & ✓ & ✗ & ✓ & ✓ & ✓ \\ \hline
5. Record modifiers & & & & & \\ in watermarks & ✓ & ✗ & ✗ & ✗ & ✗ \\ \hline
6. Copyrights protection & ✓ & ✓ & ✓ & ✓ & ✓ \\ \hline
7. Quality access control & ✓ & ✗ & ✗ & ✓ & ✓ \\ \hline
8. Fine-grained & ✓ & ✗ & ✗ & ✗ & ✗ \\ \hline \hline \end{tabular}
\end{table}
Table 1: The comparisons between Proposed Scheme and other existing related work.  
lower security levels. Thus, various areas that can be accessed by different roles in one image can be encrypted by hierarchical keys. Because of the above key-role-area model, fine-grained access control can be achieved in a more complicated and customized manner. Especially, the above method can also be applied for different layers in a single image (e.g., geographic maps). Furthermore, further traceability of image leakage (e.g., areas, layers) becomes possible due to embedded watermarks.  
Conceptualization, W.R.; Methodology, W.R. and Y.R.; Software, J.G.; Validation, T.Z.; Formal Analysis, I.G. and T.Z.; Investigation, J.G.; Resources, J.G.; Data Curation, J.G.; Writing--Original Draft Preparation, J.G.; Writing--Review & Editing, W.R., Y.R. and T.Z.; Visualization, J.G.; Supervision, W.R.; Project Administration, W.R.; Funding Acquisition, W.R. and T.Z.  
The research was financially supported by Major Scientific and Technological Special Project of Guizhou Province under Grant No. 20183001, the Open Funding of Guizhou Provincial Key Laboratory of Public Big Data under Grant No. 2017 BDKFJ006, Open Funding of Hubei Provincial Key Laboratory of Intelligent Geo-Information Processing with under Grant No. KLIGIP2016A05, and National Natural Science Foundation of China under Grant No. 61502362.  
We also thank the comments from [PERSON], [PERSON], Z.K. and M.L.  
The authors declare no conflict of interest.