# Data Privacy in the Internet of Things: A Perspective of Personal Data Store-Based Approaches
## 3 Data Privacy in the Internet of Things
### Information Privacy Protection
#### 3.3.3 Privacy-Enhancing Technologies  
PETs empower individuals to safeguard their privacy, assert control over their data, consent to personal data acquisition, and choose what information they wish to release [36]. They encompass technologies, frameworks, and other components designed to protect personal data and minimize its collection and use. Moreover, PETs facilitate compliance with data protection regulations while reducing the breach's occurrence or assisting in their detection [45; 46]. [PERSON] et al. [30] have organized PETs into data-oriented and process-oriented approaches. The first focuses on data, while the last focuses on the process that protects the privacy of individuals. The data-oriented approach encompasses PETs such as data anonymization, minimization, encryption, differential privacy, zero-knowledge proofs, secret sharing, private information retrieval, and others. The process-oriented approach comprises, for instance, Privacy by Design; Privacy Requirement Engineering; Testing and Verification; Transparency, Consent, and Control; and others. [PERSON] et al. [30] categorize PETs into data-oriented and process-oriented approaches. The former emphasizes data, while the latter emphasizes processes safeguarding individuals' privacy. The data-oriented approach includes PETs like data anonymization, minimization, encryption, differential privacy, zero-knowledge proofs, secret sharing, and private information retrieval. On the other hand, the process-oriented approach encompasses strategies such as Privacy by Design, Privacy Requirement Engineering, Testing and Verification, and Transparency, Consent, and Control. [PERSON] et al. [45] provide a classification of PETs in the IoT domain and separate them into six groups. For each group, they outline objectives and privacy threats (as described in [31]) that their respective technologies can address, as observed in Table 2. \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt}} \hline \hline
**Type of PET** & **Privacy Threats Addressed** \\ \hline Control over data & Lifecycle transitions, privacy-violating interaction and presentation \\ \hline Anonymization/Pseudonymization & Identification, profiling, linkage \\ \hline Anonymous authorization & Identification, localization and tracking, profiling, privacy-violating interaction and presentation, linkage \\ \hline Partial data disclosure & Identification, localization and tracking, profiling, privacy-violating interaction and presentation, linkage \\ \hline Policy enforcement & Inventory attacks, linkage, profiling, privacy-violating interaction and presentation \\ \hline Personal data protection & Profiling, lifecycle transitions, inventory attacks, privacy-violating interaction and presentation, linkage \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Mapping between types of PETs and IoT privacy threats addressed. Control over data comprises technologies that grant individuals more control over their data, including what, where, and how data can be collected, stored, and processed. Hence, PETs in this group help mitigate IoT threats such as privacy-violating interactions and presentations, as well as lifecycle transitions. Enforcement comprises technologies able to enforce privacy policies and restrict access to personal data. Thus, individuals keep control over the data processing and limit unauthorized access. PETs in this group help mitigate IoT threats such as profiling, inventory attacks, linkage, and privacy-violating interactions and presentations. Anonymization or pseudonymization technologies aim to protect individual privacy by eliminating identifiable data. The difference between the two techniques is that anonymization refers to the process of permanently removing identifiable data so they cannot be linked back to the individual. In contrast, pseudonymization replaces identifiable data with a reversible value. PETs, in this context, can mitigate IoT threats related to identification, localization and tracking, profiling, and linkage.