Help Center> Blockchain Service> Developer Guide> Blockchain Middleware APIs> Distributed Identity (OBT)> Overview
Updated on 2023-03-07 GMT+08:00
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Overview

Distributed identity (DID) is a blockchain-based identity management technology. It allows you to create user identities, and register, issue, and verify verifiable credentials (VCs). BCS's DID is implemented based on the W3C DID and VC specifications. It provides unified, self-explainable, and portable distributed identifiers for individual and enterprise users to address privacy issues and identity authentication across departments, enterprises, and regions.

Figure 1, Figure 2, Figure 3, and Figure 4 illustrate the implementation and usage of DID.
Figure 1 DID implementation

Implementation

  1. Each role can call the Enterprise Identity Registration (with Service) and Registering a DID APIs to generate their own DID which they fully control, and then publish the DID document to the blockchain to complete identity registration. The DID of an enterprise includes information about the services the enterprise can provide in various application scenarios.

    There are three roles: issuer, holder, and verifier. Each role can be a device, an application, an individual, or an organization.

  2. VCs are used to authenticate identities. Relevant entities register and continuously maintain credential schemas on the blockchain. Holders initiate authentication requests to issuers, obtain credentials, and provide the credentials to verifiers to complete verification.
  3. Verifiers verify VCs presented by holders by using an API to ensure that holders are qualified and permitted to proceed with relevant services.

Usage

The DID middleware is a set of microservices deployed on the user side to simplify the calling of blockchain APIs. When calling the DID API, the user private key and the Fabric-signed root certificate must be transferred.

You can download the private key and certificate on the BCS console or generate them using OpenSSL. For details, see How Can I Obtain Private Keys and Certificates of Fabric Users?

Holders can apply for VCs on or off the blockchain.

  • Off-chain application: The holder sends the identity or VC data for applying for a VC to the issuer.
  • On-chain application: The holder encrypts and stores the identity or VC data for applying for a VC on the blockchain.
Figure 2 DID usage (off-chain application)

On-chain application can be online or offline, depending on whether communication channels are required between the holder and the issuer.

Figure 3 DID usage (on-chain, online application)
Figure 4 DID usage (on-chain, offline application)