# A Survey on Recent Advanced Research of CPS Security
## 3 Reviews
### Access Control
A prototype of this framework runs on an LG Nexus 4 and accepts all declared flows while rejecting the other flows with an acceptable memory overhead, QM call latency, and serialization overhead. ContexIoT [45] is a context-based permission system that gathers context information and supports fine-grained action identification. First, it observes the control flow context of a sink in apps. Then, it uses taint analysis to label the data and judge malicious operations. The authors tested ContexIoT on 283 real-world SmartApps, and the results showed that ContexIoT can recognize all illegal contexts with negligible operation delays. ProvThings [46] is a platform-centric malicious detector that generates a data provenance graph across different apps and devices. Unlike FlowFence [44] and ContexIoT [45], it tracks data flows while considering multiple devices and apps, allowing it to track complex interactions between IoT agents. ProvThings was evaluated on 236 SmartApps, and it traces all the provenance of known attack scenarios with negligible runtime and storage costs. [PERSON] et al. [66] proposed a fine-grained access control solution for IoT users, especially opportunistic users (guests). They used decentralized identifiers (DIDs) to grant or revoke guest privileges, and the DID documents are stored in decentralized systems (e.g., blockchains, distributed ledgers, and P2P networks). Moreover, this scheme is tracking-resistant, as guests only use their DIDs to access sources. SEPD [67] is an access control model that addresses the challenge of policy administration and trust inspiration in a public sphere. The owner of a space announces access control policies considering users' histories of presence in the space. It also designs a policy language based on a temporal constraint network (TCN). SEPD supports anonymous resource sharing by structuring the authorization scheme in the style of a distributed trust management framework. AWare [47] is an access control framework for Android to prevent malicious applications from abusing authorizations to gather privacy information stealthily. It links applications' operation requests with user input events and asks the user to authorize sensitive operations unambiguously. To reduce the number of explicit user authorizations, it also reuses such authorizations in duplicate scenarios. The authors implemented and evaluated AWare in a laboratory-based testbed. The results show that AWare can help users avoid authorizing unwanted operations with 2.28 decisions per application on average. [PERSON] et al. [65] proposed a privacy protection scheme for IFTTT applets. They develop an access control and information flow analysis framework based on the JavaScript information flow tracking tool JSFlow [150]. Then, they classified the applet into private and public parts, thus breaking the information flow from private sources to public sinks. The authors evaluated 279,828 IFTTT applets spanning 400 services, 30% of which were related to stealthy privacy attacks. [PERSON] et al. [48] proposed a new access-control mechanism that focuses on IoT capabilities. It better fits users' expectations rather than per-device granularities. The authors set a schedule for authentication that reduces impacts from falsely allowing or denying access. In a 425-participant online user study, they found apparent differences in desired access-control policies for different capabilities among disparate groups. Their work supports richer capabilities and interactions.