# Policy-Based Smart Contracts Management for IoT Privacy Preservation
## 3 Proposed Method: Policy-Based Smart Contract Management for IoT Privacy Preservation
### Illustrative Case Study Scenario  
In this case study, we examined a healthcare scenario in which a patient with implanted Continuous Glucose Monitoring (CGM-002) sensors utilizes a privacy-preserving IoT model to monitor and manage critical health metrics. The patient's mobile phone serves as the central hub, receiving real-time data from IoT sensors that track vital signs, including a cardiac beat rate of 90 beats per minute and a blood glucose level of 340 mmol/L. These data are processed by a healthcare service provider to assist in ongoing monitoring and intervention every 6 h (according to the patient preferences and healthcare service recommendations).  
When the patient's blood glucose level reaches a critical threshold, the system is configured to automatically send an urgent request to the hospital, ensuring rapid response. During non-critical times, the patient's device sends regular updates containinghealth metrics, helping the healthcare team maintain an overview of the patient's general health status.  
To further support the patient's privacy requirements, the user wants a private communication channel between the patient and their physician, used for secure discussions on sensitive matters like the frequency of nighttime bathroom visits (FGBN). Additionally, the patient seeks to add a newly implanted cardiac sensor (cr-001) to monitor for potential blood clotting risks. This sensor registration will extend the scope of monitoring, providing the healthcare provider with a more comprehensive view of the patient's condition.  
The scenario introduces several challenges regarding data privacy:  
* Data Ownership and Control: The patient's health data, collected through IoT sensors, is transmitted to and processed by healthcare providers, raising concerns about ownership and control.
* Consent Management: With continuous data streaming from various sensors, the patient may wish to modify data-sharing preferences dynamically. For instance, during non-critical times, they may prefer not to share certain metrics, while, in critical moments, sharing comprehensive health data could be essential for timely care. Managing these changing consent preferences and ensuring that all parties comply with the patient's current settings can be complex and require an adaptable consent mechanism.
* Data Access Authorization: The implementation of flexible yet secure access control mechanism is crucial to ensure that only authorized personnel have access according to the patient's preferences and the context.
* Data Storage and Retention Policies: Long-term data storage for healthcare purposes introduces issues regarding data retention policies. Patients may want to limit how long their data are stored or specify what data should be permanently removed once they are no longer necessary for treatment. Balancing storage for ongoing monitoring with the patient's right to have their data deleted poses a challenge in defining clear, compliant data retention policies that respect privacy.  
Addressing these privacy-related challenges is essential to ensure that patients feel safe and in control of their health data.