# An Empirical Study of a Trustworthy Cloud Common Data Model Using Decentralized Identifiers
## 3 The Extended to Identify Management Scheme for Cloud CDM
### The Basic DID Model for Cloud CDM  
In the basic model, the identity information necessary for the information subject to receiving the desired service from the verification agency is issued and submitted by the personalization agency. To ensure the validity of the identity information issued by the personalization agent, the certificate of the personalization agent is stored in a verifiable data registry. The verification body that has received the proof of identity verifies the proof in the registry and provides services. A credential is an attestation of qualification, competence, or authority issued to an entity (e.g., an individual or organization) by a third party with a relevant or de facto authority or assumed competence to do so. If research involves human subjects or is regulated by the Food and Drug Administration (FDA), it requires review and approval from an institutional review board (IRB) or the Human Subjects Office. It is the responsibility of all faculty and students to obtain IRB approval or Exempt determination before initiating any human subjects research projects. Hence, IRB uses a public DID published globally. The IRB play a role as a verifiable credential issuer. Since the researcher as holder of the credential may present the credential to anyone, the identity (via the public DID) of the issuer must be part of what the verifier learns from the presentation. The verifier can investigate (as necessary) to decide if they trust the issuer. The public DID of IRB is put on a blockchain so that it can be globally resolved. It is used to establish secure, point-to-point messaging channels between the agents of the participants. With a verifiable credential, DIDs are used as the identifier for IRB as the issuer in cloud CDM. IRB (the issuer) DID is used to uniquely identify the issuer and is resolved to obtain a public key related to the DID. That public key is then used to verify that the data in the verifiable credential did indeed come from the issuer. This public DID ensures that the verifier knows who issued the credential a holder presents. Figure 5 shows the basic DID model for cloud CDM. Node A represents a CDM provider, and Node B represents a CDM consumer. Two trust managers located in the service broker play role as agents of the CDM provider operated in Node A and the CDM consumer operated in Node B for trustily delivering the CDM (represented as \(\text{CDM}_{\text{A}\to\text{B}}\) in Figure 3). The verifiers may not fully trust the researcher without a verifiable credential (VC) and want to share only a subset of data or respond with data retrieved from a particular query. They might also want to share different subsets of data to the researcher. The grant of access may also need to be revoked, updated, or set to expire. In cloud CDM, credentials need to be issued and verified through the following application use cases:  
Figure 5: The DID-based trust model for cloud CDM. * A researcher is a member of a group of researchers of a specific subject on which he or she wants to conduct research and is assigned a role as a research participant through IRB approval and is registered. Through the IRB, researchers are provided with a certificate of research participation (issuing research participation certificate through IRB). * CDM users apply to the creation of CDM data, encryption of the generated CDM data, and proof of access service for use in distributed storage. * CDM users apply for access service verification for decryption and distributed storage of CDM data in the process of accessing the created CDM data. The following is assumed to operating environment:  
* For CDM use, researchers are registered with the CDM provider or user organization. Through the registration process, the researcher assumes that the mutual trust relationship of the cloud CDM participating organizations can be established, managed, and managed through the certificate authority (CA).