## 4 Findings
### Smart Environments  
#### 4.3.1 Smart Home  
SHIB [120] is a smart home based on the IoT-Blockchain that addresses the challenges related to the ability of extension, trust access control, and data privacy. Only the creator of ACC can add new policies, update existing ones, or remove privacy policies from the ACC blockchain. In order to use the SHIB architecture, a smart homeowner must have agreed to a smart contract with the other parties involved. Using defined policies, smart contracts are able to restrict access requests when misbehavior is sensed in the network to increase the security and privacy of home data. Compared to other existing models, this design contains a Judge Contract (JC) that can perform judgment and impose penalties on misbehavior. ELIB [121] is a model proposed to eliminate specific issues associated with blockchain technology, such as high bandwidth, limited scalability, and high computation complexity, and implement an efficient smart home design that fits IoT necessitates. Smart homes with limited resources benefit from a centralized manager that produces shared keys for data transmission and processes every incoming and outgoing request. An overlay network is generated as shown in the current ELIB model; high-equipped resources can merge with a public BC that guarantees devoted security and privacy. The suggested ELIB model includes three optimizations: a Distributed Throughput Management (DTM) strategy, certifiateless cryptography, and a lightweight consensus algorithm. Based on the experiments with several parameters, ELIB demonstrated excellent performance. LSB [122] refers to a \"Lightweight Scalable Blockchain\" that utilizes overlay networks to achieve decentralization and end-to-end security. Network nodes are grouped into clusters using a clustering algorithm (similar to [137]). A Cluster Head (CH) is elected in each cluster; it represents the node with maximum coverage (neighbors). CHs are called Overlay Block Managers (OBMs) because they manage the blockchain network. A genesis transaction must be created by overlay nodes using one of the following approaches: certificate authorities and Burn coin in Bitcoin. A genesis transaction is broadcasted from one OBM to another after verification. In order to reduce delay and mining processing overhead, they designed a consensus algorithm called distributed time-based. Cluster heads are responsible for efficiently employing the distributed trust approach among network nodes to verify new blocks. A distributed throughput management algorithm is used to ensure that the network throughput is stable enough (based on specific parameters). LSB is designed to fulfill IoT fundamental requirements such as connectivity and mobility and real-time applications. It is implemented in different scenarios that include high-resource devices and low-resource devices. The authors analyzed and discussed further aspects of LSB, such as OBM reward, auditability, and complexity. According to a security assessment, LSB is highly fault-tolerant and secure to a wide range of attacks. Further development is required to evaluate this model in real-world settings. A privacy-preserving authentication scheme is proposed to illustrate how data are collected and shared in smart home applications [123]. The proposed scheme combines three base concepts to create a secure framework: edge computing, smart contracts, and attribute-based access control. Data are transferred to the cloud securely and privately using a differential privacy method which offloads systems' heavy processing; eventually, the system scalability is increased. The proposed system architecture consists of end users, IoT devices, multi-edge servers, and the cloud. Two types of contracts are used in the attribute-based access control: register contract and access contract. The authors explained how transactions are being carried out; four phases are used: chain transaction, state delivery, request control, and initialization.