## 3 Methodology and Implementation
### Workflow of the System  
The workflow of the proposed supply chain management system is centered around the product's journey from manufacturing to its final destination. This system leverages the use of IoT-enabled circuit boards attached to products or their packaging to monitor various environmental conditions such as temperature, humidity, and potential physical damage. These circuit boards contain sensors configured according to the product's specific requirements, ensuring its safety and quality during transit. Figure 10 illustrates the handling of sensor data, showcasing how data from multiple sensor groups is processed to ensure accuracy.  
Product ownership transfers occur at various checkpoints in the supply chain, and relevant information about the product and its transfer process is logged into the blockchain ledger. This information includes data related to the product's condition at the transfer time. However, rather than directly inputting sensor data at checkpoints, the system utilizes oracles to maintain decentralization.  
The rapid evolution of Internet of Things (IoT) technology has significantly reduced the size, cost [32], and power consumption of IoT devices, making it increasingly feasible to embed such devices into a wide variety of products. Advances in microelectronics, energy-efficient computing, and miniaturization have enabled the development of compact, energy-efficient IoT sensors and circuit boards that are capable of long-term operation without requiring frequent maintenance or battery replacement. For example, developments in low-power wide-area network (LPWAN) technologies, such as LoRaWAN and NB-IoT, provide cost-effective, energy-efficient connectivity options for IoT devices over wide geographical areas, further enhancing the practicality [33] of deploying IoT-enabled tracking solutions. A pertinent example that illustrates the feasibility and effectiveness of small, IoT-enabled tracking devices is Apple's AirTag [34]. The success and widespread adoption of AirTags demonstrate the practicality and consumer acceptance of small, IoT-enabled tracking devices, providing a strong precedent for the proposed use of IoT-enabled circuit boards in product tracking and monitoring.  
The product's lifecycle involves multiple stages, from manufacturing to distribution and delivery. Key parties in this process include the manufacturer, distributor, and shipping partners. At each transfer of ownership, the product's condition is checked and recorded in the ledger. If the product's condition remains intact, payment is made to the relevant parties, and the product continues along the supply chain. The sequence diagram for the transfer of the product can be seen in Figure 11.  
A return process is initiated if any issues arise during the journey, such as damage or deviations from environmental requirements. Products with abnormalities are flagged, preventing them from advancing in the supply chain. Depending on the product's nature, these products are returned to a designated location for further assessment, including examination and potential repair. The sequence diagram for the return transfer of the product can be seen in Figure 12.