## 4 Multiple Authentication Methods Using DID in the Blockchain
### Analysis and Evaluation of the Proposed Method  
In the method proposed in this study, a user's ID, password, and facial information, which is the minimum necessary information for user authentication, are stored, and authentication is performed by comparing and verifying the hash value of biometric authentication information from the DID blockchain.  
Through the system design, the structure of the basic DID blockchain system was defined, and the authentication system could be implemented by utilizing the system structure.  
The system proposed in this study is an authentication model that combines ID/PW and biometric information and stores it in a blockchain, which guarantees more stability than the one-step authentication method. In addition, as of November 2020, the accredited certificate system was abolished in Korea, and Internet banking has been implemented  
Figure 9: Multi-factor authentication.  
through various authentication methods. Therefore, this study makes it possible to enter various certificate markets.  
The system proposed in this study can have the following advantages.  
The requirements for an effective multi-factor authentication system are as follows.  
1. Because the account information is recorded on the blockchain using blockchain technology, the integrity of the blockchain is guaranteed, so there is no possibility of hackers tampering with the user's account information;
2. There is a possibility that biometric authentication may not properly authenticate a user. Therefore, security is guaranteed by applying two or more authentication techniques through multi-factor authentication;
3. Due to the widespread use of smartphones, the proposed technique is authentication using a smartphone possessed by a user, so authentication proceeds in a simple and easy way.  
First, if biometric information such as facial recognition technology is stored in the DID blockchain and distributed, it is difficult to find out what kind of data it actually is without confirmation from the service provider, even if anyone can access it. Therefore, the security and safety of user authentication information can be improved through confidentiality through biometric technology.  
Secondly, the service provider cannot misuse biometric information. Even if someone wanted to access the DID blockchain and combine distributed and stored data, data abuse by the system provider can be avoided because there is no authentication information held by the user, and it can be safely stored from attacks by external attackers.  
Third, the existing technique requires the user to change their ID and password at regular intervals, but in the proposed technique, there is no need to change the biometric information stored in the blockchain because it is the basis for the authentication. Therefore, user convenience can be improved;  
4. Since the proposed technique performs authentication through multi-factor authentication, legitimate users are not unauthenticated due to the basic user identification that is performed in Step 1, and illegitimate users are not erroneously authenticated due to the biometric authentication performed in Step 2.