## 4 Findings
### Healthcare
The proposed architecture consists of three tiers, namely network nodes (constrained and unconstrained), number of authorities (medical institutions and organizations), and EHRs cloud providers (servers). PBE-DA is designed in a multi-tier blockchain framework that uses Elliptic Curve Cryptography (ECC). The fog or access layer is the initial tier to connect devices and patients using a gateway. The ledger distribution and communication of different EHRs are analyzed in the second tier. Finally, compliance issues between EHR providers are examined. MIRACL security tools are used to evaluate the framework for various security functions. A study discussed how the volume of medical imaging is increasing, which might affect the diagnosis and treatment because these images must be retrieved first [104]. This study presents a threat and a layered architecture based on blockchain that selects feature vectors to handle large-size images. To ensure the privacy of medical images and their features, a customized transaction structure was designed in addition to the feature vector. This study focused on three types of threats from a security perspective: data forgery, data tampering, and privacy disclosure. The system design includes five entities: hospital, third party, image retrieval service, regulatory authority, and miner. Transaction generation,image feature encryption, and image feature extraction are the main components of the transaction layer. Based on the encrypted image characteristics, the service layer provides crucial functionality for similarity measurement and image retrieval. Introducing the medical field to IoT has led to reduced cost, increased accuracy, and improved efficiency; security and privacy aspects are still essential concerns due to the heterogeneous network that contains various entities and a large amount of data. One possible solution is to introduce an IoMT authentication framework integrated with blockchain technology to create a general architecture that can eliminate the issues mentioned earlier [105]. Elliptic Curve Cryptography (ECC) and Physically Unclonable Functions (PUFs) are authentication schemes between system components. Five phases are included in the proposed schemes: revocation phase, password and biometrics update, login and authentication, registration, and system initialization. Multiple procedures are performed in these phases, such as creating a blockchain network, setting up the cryptographic parameters, registering the entities with the Register Center (RC), initializing authentication between entities, updating certain information, and summarizing the actions to be performed when a private key is lost or compromised. The proposed scheme achieves the desired security and operational requirements based on the security and performance analysis. Regular and remote monitoring of patients with chronic diseases is critical due to their unpredictable health conditions. Metrics such as scalability, processing time, and security are essential when implementing a blockchain-based and proxy re-encryption healthcare system [106]. The proposed system architecture comprises hospitals, physicians, and patients linked with the ministry of health through the blockchain network. IPFS is used to store the collected and encrypted health data. Patients are supported with IoT medical devices that collect health data and a smartphone that acts as a bridge with the medical entities. To speed up the consensus process and data storage, the Clique PoA algorithm is implemented in the system. Compared to the state-of-the-art methods, the proposed system offers high security. GarliMediChain [107] is a health data-sharing anonymous system that ensure privacy, anonymity, and low latency by integrating blockchain technology with garlic routing. In addition, to maximize institutions' payoffs, a coalition system is introduced. Fictitious play is used to enforce trust among coalition groups.