*3.4.1 System architecture*

In [4], the blockchain-based components of the decentralized authentication system are described. **Figure 6** illustrates the system's architecture. The components of the proposed system are outlined below:

• Ethereum Smart Contract:

This authentication system's contract is used to handle user registration and authentication. The agreement would require data such as the email, password, *A Simulation Model of a Blockchain-Based Decentralized Patient Information Exchange… DOI: http://dx.doi.org/10.5772/intechopen.109591*

#### **Figure 5.**

*Conceptual view of the tier-based health monitoring architecture [7].*

#### **Figure 6.**

*The fog-enabled blockchain-based authentication system's system architecture [4].*

and the UserEthAdr to enlist clients upon enrollment and to validate clients in the ensuing collaboration with the framework [4].

• Fog Node:

Devices that serve as blockchain nodes and servers are known as fog nodes. Every node has a duplicate of the BlockC, LDG, and SmContract. When a User registration or authentication transaction takes place on a node, the BlockC information there is updated. To host or be a part of the BlockCN, the fog device or fog server must meet sufficient requirements [4].

• Edge Devices:

During registration and authentication, the user's end devices are mapped to nodes. The BlockC cannot be hosted on these devices due to a lack of resources [4].

• Cloud:

IoT data are stored, hosted, and computed in the cloud, which is a large storage unit. Data generated by IoT or edge devices must be processed and analyzed by this cloud server [4].
