# Securing Blockchain-Based Supply Chain Workflow against Internal and External Attacks
## 2 Proposed Methodology
### Constraints
**Warehouse module**, which performs the following operations: * Inspection of products--by inspecting the received product for compliance with the agreed purchase specification. * Paying the cost--by paying the desired amount. The sketch of the application is shown in Figure 3, which illustrates the process of initiating a purchase requisition. The simplified workflow of the application is as follows:

1. Issue a purchase requisition. 2. Obtain a quotation from different suppliers. 3. Approve the best bid for the product. 4. Obtain the supply from the chosen supplier. 5. Receive the products and inspect them. 6. Pay the amount. The detailed workflow is explained in the following section through an example case study. ## 5 Example Case Study

In this section, we show the applicability of our application with a case study involving a local stakeholder's real-time supply chain process. In our case study, we developed a prototype to simulate the actual requirements from the real stakeholder. To demonstrate the effectiveness of our methodology, we first describe the current supply chain process as experienced by the stakeholder, followed by a description of how our approach was used to automate the example process. ### Supply Chain Process

Based on our discussions with local stakeholders, we developed a specific supply chain process that demonstrates the handling of the supply for various items, including hardware, by a stakeholder. As shown in Table 1, the process involves _internal_ and _external_ entities, where the former entities are part of the process organization, while the latter entities do not belong to the process organization. Figure 3: Supply chain ICT application. As depicted in Figure 4, the supply chain process involves three stages that are discussed below:

1. The procurement department initiates the demand (supply requirements) of items by issuing a purchase requisition (PR), which is 1. Later reviewed by another division of procurement that ensures the specification of the requested items; and 2. After review, the PR is sent to the financial department to check the availability of finances to handle/supply the requested items. If the financial department does not approve, then re-evaluation of the PR is requested to the PR initiator. 2. If the financial feasibility of the PR is approved, then various suppliers are contacted after asking for tenders. Later, 1. Each supplier issues a quotation for the items as asked in the PR, which is later approved/disapproved by the procurement; and 2. For those suppliers, whose quotation is approved by the procurement, they start preparing items for supply along with their documentation, and finally, all prepared supply is delivered to the warehouse of the process organization. 3. When the requesting warehouse receives delivery of the items, then 1. The warehouse inspects the delivered items to ensure they received the product as per specification (i.e., PR). The process of inspection of items may involve external entities, for instance, manufacturers who manufactured those products and/or other entities that could provide some certified testing and attestation of the product as per the given PR specification. 2. If the products received are consistent with the PR-based specification of those products, then the financial department of procurement pays the amount to the supplier and stores the products in the warehouse after their registration. 3. If the products received are not consistent with the PR specification, then the procurement contacts the supplier and investigates the reason for inconsistency, until the matter is settled. The settlement is done in various ways, for instance, by replacing the delivered products, opting for another supplier, or a deduction in payment for the breach of contract. The example supply chain process is typical in various industrial stakeholders. However, the only difference is in the implementation of this process, which is the main hindrance in realizing the process in true spirit.