Identity Protocol

Elastos implements W3C Decentralized Identifiers (DIDs) anchored on the EID chain (Chain ID 22). DIDs use the P-256 curve — the same as the main chain, not Ethereum's secp256k1. This page covers the DID method specification, document format, on-chain storage, and resolution.

DID Method

Property	Value
Method	did:elastos
Spec version	v0.2
Anchoring chain	EID (Chain ID 22)
Curve	P-256 (secp256r1)
Case sensitive	Yes
Example	did:elastos:icJ4z2DULrHEzYSvjKNJpKyhqFDxvYV7pN

Address Derivation

1. Generate P-256 key pair from HD path m/44'/0'/0'/0/<index>
2. Build redeem script: 0x21 || compressed_pubkey || 0xAC
3. Hash: SHA-256 then RIPEMD-160 (20 bytes)
4. Prepend version byte 0x67 (DID prefix)
5. Append checksum (first 4 bytes of double-SHA-256)
6. Base58 encode — address always starts with i
7. DID = did:elastos:i<address>

warning

The DID address uses P-256, not secp256k1. Standard Ethereum/Bitcoin key derivation cannot produce valid Elastos DID keys.

DID Document

{
    "@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": "<base58-P256-pubkey>"
    }],
    "authentication": ["did:elastos:icJ4z2DULrHEzYSvjKNJpKyhqFDxvYV7pN#primary"],
    "verifiableCredential": [],
    "service": [{
        "id": "#hivevault",
        "type": "HiveVault",
        "serviceEndpoint": "https://your-hive-node.example.com"
    }],
    "expires": "2027-01-01T00:00:00Z"
}

On-Chain Format

DID operations are submitted as EVM transactions on EID targeting precompile 0x16. Each operation contains:

Component	Description
Header	Operation type (create, update, deactivate), spec version, previous tx hash (for updates)
Payload	Base64-encoded DID document JSON
Proof	P-256 signature over header + payload, with verification method reference

Resolution Algorithm

1. Query EID node via did_resolveDID JSON-RPC
2. Retrieve all transactions for the DID from the chain
3. Validate each transaction's P-256 signature
4. Replay operations chronologically:
   • create — initial document
   • update — apply changes (must be signed by controller)
   • deactivate — mark DID as deactivated
5. Return final document + status (valid / deactivated / not-found)
6. Cache result locally (configurable TTL)

Verifiable Credentials

Credentials follow the W3C Verifiable Credentials specification:

{
    "@context": ["https://www.w3.org/2018/credentials/v1"],
    "type": ["VerifiableCredential", "KYCCredential"],
    "issuer": "did:elastos:issuerDID",
    "credentialSubject": {
        "id": "did:elastos:holderDID",
        "name": "John Doe"
    },
    "proof": {
        "type": "ECDSAsecp256r1",
        "verificationMethod": "did:elastos:issuerDID#primary",
        "signature": "<base64-signature>"
    }
}

Credential types (from Elastos.DID.Contexts): ApplicationProfileCredential, InternetAccountCredential, SocialCredential, WalletCredential.

SDK Support

Language	Repository	Key Classes
TypeScript	Elastos.DID.JS.SDK	DIDStore, RootIdentity, DID, DIDDocument, VerifiableCredential
Java	Elastos.DID.Java.SDK	Same hierarchy, bitcoinj for HD derivation
C	Elastos.DID.Native.SDK	Core implementation, libsodium
Swift	Elastos.DID.Swift.SDK	iOS/macOS bindings