# A Watermark-Based In-Situ Access Control Model for Image Big Data
## 2 Related Work  
The topic of watermarks has been explored for decades. Due to powerful software and personal computers, there has emerged considerable unauthorized copying and distribution of digital content, such as e-books, videos, and digital images. To solve this problem, watermarks are usually used to verify and protect the copyrights [4; 5; 6]. In the above methods, both fragile watermarks and robust watermarks are coded as a legal label instead of as a control technique. Additionally, many methods have been proposed to detect the modification of images[7; 8], but they are unable to find the modifier or prevent such modifications. In recent years, several watermark schemes have been put forward for access control. Watermarks used for permitting hierarchical access control and protecting the content of visual medical information were proposed [9]. However, original images are not encrypted in this scheme. A removable and visible watermarking by combining block truncation coding and chaotic map is proposed in [10], which can be applied in copyright notification and access control in mobile communication. They proposed two-stage watermarks that blur original images before visitors pass access control, and only authorized visitors can attain clear images. However, it is not a hierarchical access control. [PERSON] proposed a data hiding scheme for access control and error concealment in digital images [11]. He also proposed a data hiding method that integrates access control and authentication in a single platform, especially for cover images [12]. Encrypted digital images are displayed in lower quality before watermarks are read. To summarize, the schemes above display images in lower-quality formats before visitors obtain permissions. The access control strategies are still not coded in watermarks. Quality access control is are used in audio watermarks. [PERSON] et al. proposed a combination of both encryption and audio watermarking. This method is used for the safe distribution of audio content over public networks, whereby only authorized users can access the high-quality content, while other users can only access a low-quality content [13]. Watermarks can be used in video files to identify pirates, which can be extracted at the decoder and used to determine whether the video content is watermarked [14]. We stress that our proposed scheme for integrating access control policies as watermarks can also be applied in audio files or video files, although we concentrate on images in this paper. Geologic mapping and the design of geologic (thematic) maps are currently supported by Geographic Information Systems (GIS). In order to gain a high degree of efficiency and to allow the exchange of a common structured framework, map data models have been designed by agencies and individuals in order to support their mapping process. File-based geo-databases are much more accessible, but still suffer from a number of administrative limitations [15]. A new access control mechanism that combines trust and role-based access control models is presented in [16]. [PERSON] proposes a multi-layer based access control model for GIS mobile web services [17]. The objective of such spatially-aware access control models is to regulate the access to protect objects based on the position information. [PERSON] proposed role-based access control with spatial constraints [18]. [PERSON] et al. proposed a fine-grained access control model for spatial data in a grid environment based on a role-based access control model [19]. Furthermore, a multi-granularity spatial access control model was proposed that introduces more types of policy rule conflicts than single-granularity objects [20]. The model can manage and enforce the strong and efficient access control technology in large-scale environments. However, all of these access control strategies are not encoded into watermarks, and access control still relies on servers. In recent years, Quick Response (QR) codes have been popular due to their efficiency and security.