# Blockchain-Based Badge Award with Existence Proof
## 3 Digital Badge System with Blockchain Support
### Digital Badge Instance  
Originally, there is two types of methods to distinguish assertion information: hosted type and signed type. Also, conventional Badgr does not natively support the ability to store data in the blockchain. That is, conventional Badgr manages the information of the badge itself and stores the information according to the specification defined by OpenBadges. (1) If an assertion uses \"hosted\" verification and there is no cryptographic signature to verify that the full document here is the exact one published by the issuer, the verifier and displayer platforms will likely discard the embedded Badge Class and issuer Profile here and replace them with the values discovered at their id URIs, because only those hosted documents can be trusted to be created by the issuer. (2) If an assertion uses \"signed\" verification, the validator may accept the embedded values as the intended Badge Class and issuer Profile, and if they have multiple records for those entities that use the declared id, the validator may choose how to index and present that information. The issuer's should change the ids of their Badge Classes when they make edits if they wish the edits to be essentially understood as a different achievement than the one published under the original id.  
Figure 9 shows the flow chart of the platform operation developed in this study. As shown in the figure, the digital badges and certifications are issued by the issuing authority to the student, and they are also recorded by the issuing authority to generate blockchain transactions. Backpack is a badge repository, the original concept of which was proposed by Mozilla. Digital badges and certifications are verified by the certification verifier on the Bitcoin blockchain in regression test mode or the Ropsten Ethereum network [26]. The regression test mode of Bitcoin is used to establish a new blockchain with private control but has the same rules as the public Bitcoin network. This mode is specially used for research and development purposes, where the rules are predefined. Any individual or organization can create an Issuer profile and begin defining and issuing digital badges. Any entity that can be described with a name, description, URL, image, and email address is a possible candidate to become an Issuer. To issue a digital badge, we need a technology platform that is compatible with the Open Badges specification [12].  
Figure 8: Digital badge assertion information with extension of blockchain in this research.  
We used a total of four servers to develop the proposed system. The first is a web server for providing the user UI. The second is a REST API server for performing operations conforming to the Open Badge standard. The third is a blocker server for recording transactions in the blockchain. The fourth is a blockchain network. In this study, the Bitcoin server in the regression test mode is used for Bitcoin and the Ropsten test network [26] is used for Ethereum. In this study, all the servers were implemented in the AWS EC2 cloud platform as shown in Figure 10.