Working with DIDs

Elastos DIDs are W3C-compliant Decentralized Identifiers anchored on the EID chain. They follow the format did:elastos:i<base58-encoded-id>. The JavaScript SDK implements the W3C DID Core profile used on EID: create and publish documents, issue credentials, and resolve others’ DIDs on-chain.

DID Architecture

┌──────────────────────────────────────────────────────┐
│                    DID Document                       │
│                                                       │
│  DID: did:elastos:icJ4z2DULrHEzYSvjKNJpKyhqFDxvYV7pN │
│                                                       │
│  ┌─────────────────────────────┐                      │
│  │  Public Keys                │                      │
│  │  - authentication key       │                      │
│  │  - assertion key            │                      │
│  └─────────────────────────────┘                      │
│                                                       │
│  ┌─────────────────────────────┐                      │
│  │  Services                   │                      │
│  │  - Hive vault endpoint      │                      │
│  │  - Carrier address          │                      │
│  └─────────────────────────────┘                      │
│                                                       │
│  ┌─────────────────────────────┐                      │
│  │  Verifiable Credentials     │                      │
│  │  - Self-proclaimed          │                      │
│  │  - Third-party issued       │                      │
│  └─────────────────────────────┘                      │
└──────────────────────────────────────────────────────┘
         │
         │  IDChainRequest transaction
         ▼
┌──────────────────┐
│   EID Chain       │
│   (Chain ID: 22)  │
│                   │
│  Precompiled      │
│  contracts:       │
│  - 0x16 (22)      │  ← operationDID (create/update/deactivate)
│  - 0x17 (23)      │  ← resolveDID (resolve DID documents)
│  - 0x7D7 (2007)   │  ← KYC operations
└──────────────────┘

SDK Installation

npm install @elastosfoundation/did-js-sdk

Configure the resolver (`DIDBackend`)

Point the SDK at mainnet or testnet before any DID operation:

import { DIDBackend, DefaultDIDAdapter } from "@elastosfoundation/did-js-sdk";

// Mainnet
DIDBackend.initialize(new DefaultDIDAdapter("https://api.elastos.io/eid"));

// Testnet
DIDBackend.initialize(new DefaultDIDAdapter("https://api-testnet.elastos.io/eid"));

Single global resolver

Call DIDBackend.initialize() once at application startup. Calling it again replaces the global resolver and can cause confusing resolution behavior.

Key Classes

Class	Purpose
`DIDStore`	Persistent storage for DID documents and private keys
`RootIdentity`	Root identity derived from HD mnemonic
`DID`	A decentralized identifier reference
`DIDDocument`	The full document associated with a DID
`DIDURL`	URL format for referencing DID resources
`VerifiableCredential`	A signed credential (claim about a subject)
`VerifiablePresentation`	A package of credentials presented to a verifier
`Issuer`	Entity that creates and signs credentials

DIDStore operations

Operation	Method	Description
Open / create store	`DIDStore.open(path)`	Opens an existing store or creates one at the given path
Load a DID	`store.loadDid(did)`	Loads a DID document from local storage
List DIDs	`store.listDids()`	Lists DIDs in the store
Delete a DID	`store.deleteDid(did)`	Removes a DID and its keys from local storage
Export	`store.exportDid(did, password, storepass)`	Exports a DID (with keys) as encrypted JSON
Import	`store.importDid(exportedJson, password, storepass)`	Imports a previously exported DID
Sync	`store.synchronize(identity, storepass)`	Pulls the latest DID documents from the chain into the store

Creating a DID Identity

import {
  DIDStore,
  RootIdentity,
  DID,
  DIDDocument,
  Mnemonic,
  DIDBackend,
  DefaultDIDAdapter,
} from "@elastosfoundation/did-js-sdk";

// Initialize the DID backend resolver
const resolver = new DefaultDIDAdapter("https://api.elastos.io/eid");
DIDBackend.initialize(resolver);

// Create or open a DID store
const store = await DIDStore.open("/path/to/did-store");

// Generate a new mnemonic or use existing one
const mnemonic = Mnemonic.generate("english");

// Create root identity from mnemonic
// Derives keys at m/44'/0'/0'/0/<index> using P-256 curve
const rootIdentity = RootIdentity.createFromMnemonic(
  mnemonic,
  "",           // passphrase (empty for default)
  store,
  "storepass"   // store encryption password
);

// Create the first DID document (index 0)
const doc = await rootIdentity.newDid("storepass");
const did = doc.getSubject();
console.log("Created DID:", did.toString());
// Output: did:elastos:icJ4z2DULrHEzYSvjKNJpKyhqFDxvYV7pN

Back up the mnemonic

The mnemonic is the master secret for every DID derived from this RootIdentity. Store it offline; losing it means losing access to those DIDs permanently.

Publishing a DID Document

Publishing anchors the DID document on the EID chain via an IDChainRequest transaction:

// Publish the DID document to the EID chain
await doc.publish("storepass");

// The SDK handles:
// 1. Serializing the DID document to JSON
// 2. Creating an IDChainRequest transaction
// 3. Signing with the DID's private key
// 4. Submitting to the EID chain

// Wait for confirmation (usually 10-20 seconds on EID)
// Then resolve to verify
const resolvedDoc = await DID.resolve(did);
console.log("Resolved:", resolvedDoc !== null);

info

DID publication requires at least one EID block confirmation. EID block time is approximately 5-10 seconds, but network conditions can vary. See Common Pitfalls for retry strategies.

Resolving a DID with the SDK

After a DID is published, you can resolve its document from the chain using a DID instance (this uses the same DIDBackend you initialized earlier):

import { DID } from "@elastosfoundation/did-js-sdk";

const did = new DID("did:elastos:icJ4z2DULrHEzYSvjKNJpKyhqFDxvYV7pN");
const doc = await did.resolve();

if (doc) {
  console.log("Public keys:", doc.getPublicKeyCount());
  console.log("Services:", doc.getServiceCount());
  console.log("Expires:", doc.getExpires()?.toISOString());
} else {
  console.log("DID not found on chain");
}

Resolution delay

A DID that was just published may take roughly 10–20 seconds to become resolvable while EID confirms blocks.

Issuing Verifiable Credentials

import { Issuer, VerifiableCredential, DIDURL } from "@elastosfoundation/did-js-sdk";

async function issueCredential(
  issuerDoc: DIDDocument,
  subjectDID: DID,
  storepass: string
): Promise<VerifiableCredential> {
  const issuer = new Issuer(issuerDoc);

  const credentialId = DIDURL.from("#emailCredential", subjectDID);

  const vc = await issuer.issueFor(subjectDID)
    .id(credentialId)
    .type("EmailCredential", "BasicProfileCredential")
    .property("email", "[email protected]")
    .property("name", "Jane Developer")
    .property("timestamp", new Date().toISOString())
    .expirationDate(new Date(Date.now() + 365 * 24 * 60 * 60 * 1000)) // 1 year
    .seal(storepass);

  console.log("Credential ID:", vc.getId().toString());
  console.log("Issuer:", vc.getIssuer().toString());
  console.log("Subject:", vc.getSubject().getId().toString());

  return vc;
}

Creating Verifiable Presentations

import { VerifiablePresentation } from "@elastosfoundation/did-js-sdk";

async function createPresentation(
  holderDoc: DIDDocument,
  credentials: VerifiableCredential[],
  nonce: string,
  realm: string,
  storepass: string
): Promise<VerifiablePresentation> {
  const vp = await VerifiablePresentation.createFor(
    holderDoc.getSubject(),
    credentials,
    nonce,
    realm,
    storepass,
    holderDoc.getStore()!
  );

  console.log("Presentation holder:", vp.getHolder().toString());
  console.log("Credentials count:", vp.getCredentialCount());
  return vp;
}

Verifying Credentials and Presentations

async function verifyCredential(vc: VerifiableCredential): Promise<boolean> {
  // Checks:
  // 1. Signature is valid (signed by issuer's key)
  // 2. Credential is not expired
  // 3. Issuer DID is resolvable and not deactivated
  // 4. Credential has not been revoked
  const isValid = await vc.isValid();

  if (!isValid) {
    // Check specific failure reasons
    const isExpired = vc.isExpired();
    const isGenuine = await vc.isGenuine();
    console.log("Expired:", isExpired);
    console.log("Genuine signature:", isGenuine);
  }

  return isValid;
}

async function verifyPresentation(vp: VerifiablePresentation): Promise<boolean> {
  const isValid = await vp.isValid();

  if (isValid) {
    const holder = vp.getHolder();
    const credentials = vp.getCredentials();
    for (const cred of credentials) {
      console.log(`Credential ${cred.getId()}: subject=${cred.getSubject().getId()}`);
    }
  }

  return isValid;
}

Resolving DIDs On-Chain

DIDs are resolved by calling the precompiled contract at address 22 (0x16) on the EID chain:

import { ethers } from "ethers";

async function resolveDIDOnChain(didString: string): Promise<object | null> {
  const provider = new ethers.JsonRpcProvider("https://api.elastos.io/eid");

  const result = await provider.call({
    to: "0x0000000000000000000000000000000017", // resolveDID (address 23)
    data: ethers.hexlify(ethers.toUtf8Bytes(didString)),
  });

  if (result === "0x") return null;

  const docJson = ethers.toUtf8String(result);
  return JSON.parse(docJson);
}

// Usage
const doc = await resolveDIDOnChain("did:elastos:icJ4z2DULrHEzYSvjKNJpKyhqFDxvYV7pN");
if (doc) {
  console.log("DID Document:", JSON.stringify(doc, null, 2));
}

tip

For more details on EID precompiled contracts, see ESC Precompiled Contracts.

DID Document Structure

A resolved DID document looks like this:

{
  "@context": "https://www.w3.org/ns/did/v1",
  "id": "did:elastos:icJ4z2DULrHEzYSvjKNJpKyhqFDxvYV7pN",
  "publicKey": [
    {
      "id": "did:elastos:icJ4z2DULrHEzYSvjKNJpKyhqFDxvYV7pN#primary",
      "type": "ECDSAsecp256r1",
      "controller": "did:elastos:icJ4z2DULrHEzYSvjKNJpKyhqFDxvYV7pN",
      "publicKeyBase58": "27bqfhMew5hEFLYp2kFnhCrJrij7Z6xPSQq6dBgKmyJBw"
    }
  ],
  "authentication": [
    "did:elastos:icJ4z2DULrHEzYSvjKNJpKyhqFDxvYV7pN#primary"
  ],
  "verifiableCredential": [
    {
      "id": "did:elastos:icJ4z2DULrHEzYSvjKNJpKyhqFDxvYV7pN#name",
      "type": ["SelfProclaimedCredential"],
      "issuer": "did:elastos:icJ4z2DULrHEzYSvjKNJpKyhqFDxvYV7pN",
      "issuanceDate": "2024-01-15T10:00:00Z",
      "credentialSubject": {
        "id": "did:elastos:icJ4z2DULrHEzYSvjKNJpKyhqFDxvYV7pN",
        "name": "Jane Developer"
      }
    }
  ],
  "service": [
    {
      "id": "did:elastos:icJ4z2DULrHEzYSvjKNJpKyhqFDxvYV7pN#hivevault",
      "type": "HiveVault",
      "serviceEndpoint": "https://your-hive-node.example.com"
    }
  ],
  "expires": "2029-01-15T10:00:00Z",
  "proof": {
    "type": "ECDSAsecp256r1",
    "verificationMethod": "did:elastos:icJ4z2DULrHEzYSvjKNJpKyhqFDxvYV7pN#primary",
    "signature": "..."
  }
}

SDKs in other languages

Language	Repository
Java	Elastos.DID.Java.SDK
Swift	Elastos.DID.Swift.SDK
C/C++	Elastos.DID.Native.SDK

Future: Runtime DID Bridge

Planned Feature

The ElastOS Runtime currently uses did:key (Ed25519, locally generated) for device identity and message signing. A bridge from the runtime's did:key to on-chain did:elastos DID is planned but not yet available. When implemented, this will allow runtime identities to anchor to the EID chain, connecting local device identity with globally verifiable on-chain identity. See the Runtime Roadmap for status.

Resources

GitHub — DID JS SDK
DID Login tutorial — authenticate users with DIDs
W3C DID Core

DID Architecture​

SDK Installation​

Configure the resolver (DIDBackend)​

Key Classes​

DIDStore operations​

Creating a DID Identity​

Publishing a DID Document​

Resolving a DID with the SDK​

Issuing Verifiable Credentials​

Creating Verifiable Presentations​

Verifying Credentials and Presentations​

Resolving DIDs On-Chain​

DID Document Structure​

SDKs in other languages​

Future: Runtime DID Bridge​

Resources​