# Policy-Based Smart Contracts Management for IoT Privacy Preservation
## 2 Related Works
### Research Works  
In [20], authors aim at overcoming the central processing of IoT devices and communication by deploying blockchain technology. The proposed private Ethereum blockchain network controls the IoT device's communication via several smart contracts defined according to data owner privacy settings. Their approach controls the interaction between the IoT devices of the owner without communicating their data to outside networks. This enables owners to manage their IoT devices locally. However, in many cases, IoT device data need to be shared with external parties to analyze them and provide other services. In the same context, [PERSON] et al. [1] used the public Ethereum platform to enhance the privacy of IoT systems and devices. They used the Message Queue Telemetry Transport (MQTT) protocol for quick and stable communications as well as anonymization to conceal a person's identity. They deployed Stor] to save sensitive data. The user may define the nodes that could access their data, which is not always practical since, mostly, the serviceprovider determines the node to process user data. Usage of smart contracts to detect any abnormal data sensed by IoT devices monitoring patients in their homes was discussed in [21]. The paper proposes to implement the Ring signature encryption method to preserve the anonymity of the person who signed the message. [PERSON] et al. [22] proposed to use software-defined networking (SDN) technology to determine the fog nodes within blockchain networks, thus enabling access to IoT devices and systems securely and at low cost. The authors propose a distributed blockchain cloud architecture composed of the device, fog, and cloud layers. However, their approach lacks information about location privacy. A decentralized IoT service platform, called DISP, for secure Machine-to-Machine (M2M) and Machine-to-Human (M2H) communications within an IoT system using a private blockchain platform was discussed in [23]. Communications between IoT devices and individuals are achieved through blockchain messages. [PERSON] et al. [24] deployed OSCAR (Object Security Architecture for the Internet of Things) technology to provide trust between communicated parties in a smart city environment. OSCAR manages the authorized clients' access to the public ledger of the blockchain network. [PERSON] et al. [25] encrypted the data on the user's side before uploading them to the distributed blockchain ledger. They used homomorphic encryption to enable anonymous search of the keywords using the blockchain users' API. [PERSON] et al. [26] addressed the data access control problem in IoT by using blockchain technology integration to enable the users to directly manage authorizations using a decentralized Context-Aware Authorization approach without going through a trusted third-party authority. They proposed separating peer-to-peer IoT tenant transactions and creating a hybrid model connecting the main blockchain to its subnetwork blockchain(s). [PERSON] et al. [27] proposed adding a connectivity position named a bridge. Every transaction received by the bridge is privacy-aware and anonymized using the k-anonymity algorithm. The proposed approach is dedicated to energy transactions in IoT ecosystems. In [28], the authors deployed the Pillier cryptosystem and an identity-based signature scheme for verifiable record aggregation to preserve the privacy and real identity of vehicular drivers. [PERSON] et al. [29] incorporated the differential privacy of individual data before sending them to the blockchain network. The goal is to preserve individual identity privacy while keeping the information useful to complete the transaction. A machine learning method was used after applying differential privacy mechanisms before outsourcing them to the cloud. [PERSON] et al. [30] introduced the Ant Colony optimization with Multi-Kernel Support Vector Machine to preserve the privacy of users.