Prisma DIDs – Cardano Integration Plan

Document Type: Technical Integration Specification Version: 1.0 Date: December 9th, 2025 Authors: Prisma Team Status: Active

Specification

1. Cardano Standards Compliance

CIP-10: Metadata Label Registry

Prisma DIDs uses registered CIP-10 labels for all on-chain data:

Note: Labels are in the application-specific range (1-65535). Formal CIP-10 registration to be submitted post-MVP.

Custom Organization Labels:

Organizations deploying their own VC Indexer can register additional CIP-10 labels for their credential types. The label schema must be compatible with the base VCEventPayload structure.

CIP-20: Transaction Metadata

All Prisma DIDs data is stored as CIP-20-compliant transaction metadata:

{
  "199674": {
    "id": "did:cardano:stake1u9...",
    "ipfs": "bafybeig...",
    "action": "create",
    "v": 1,
    "prev": null,
    "payloadSig": "{\"key\":\"...\",\"sig\":\"...\",\"address\":\"...\"}"
  }
}

Metadata Constraints:

• Strings limited to 64 bytes (chunked with _0, _1 suffixes if needed)
• Total metadata size limited to ~16KB per transaction
• JSON must be valid UTF-8
• Null values must be converted to empty strings ("") for Cardano metadata compatibility

CIP-30: Wallet dApp Connection

Prisma DIDs uses the following CIP-30 methods:

Wallet Compatibility:

• Eternl ✅
• Lace ✅
• Nami ✅
• Flint ✅
• Typhon ✅

2. DID Method: did:cardano

Identifier Format

did:cardano:<stake-address>

Where <stake-address> is the bech32-encoded stake address from getRewardAddresses()[0].

Example:

did:cardano:stake1u9rqg7a3skqzx8jxzvm9k2w3c5k6h7j8l9m0n1p2q3r4s5

DID Document Storage

DID Documents are stored on IPFS and referenced by CID in metadata:

{
  "@context": [
    "https://www.w3.org/ns/did/v1",
    "https://w3id.org/security/suites/ed25519-2020/v1"
  ],
  "id": "did:cardano:stake1u9...",
  "controller": "did:cardano:stake1u9...",
  "verificationMethod": [
    {
      "id": "did:cardano:stake1u9...#key-0",
      "type": "Ed25519VerificationKey2020",
      "controller": "did:cardano:stake1u9...",
      "publicKeyMultibase": "z6Mk..."
    }
  ],
  "authentication": ["did:cardano:stake1u9...#key-0"],
  "assertionMethod": ["did:cardano:stake1u9...#key-0"]
}

On-Chain Event Schema

DID Event Payload:

interface DIDEventPayload {
  id: string; // did:cardano:stake1...
  ipfs: string; // IPFS CID of DID Document
  action: 'create' | 'update' | 'revoke';
  v: number; // Version (1, 2, 3, ...)
  prev: string | null; // Previous tx hash (null for create)
  payloadSig: string; // JSON-stringified PrismaPayloadSig
}

Signature Wrapper:

interface PrismaPayloadSig {
  key: string; // Ed25519 public key (hex)
  sig: string; // Ed25519 signature (hex)
  address: string; // Signing address (bech32)
}

3. VC Anchoring

VC Event Schema

interface VCEventPayload {
  event: 'issue' | 'validate' | 'revoke';
  issuerDid: string;
  holderDid: string;
  vcHash: string; // jti for SD-JWT, SHA-256 for Ed25519
  vcType: string; // e.g., "ContributionCredential"
  vcFormat: 'sd-jwt' | 'ed25519' | 'bbs'; // REQUIRED
  validatorDid?: string; // For validate events
  reason?: string; // For revoke events
}

On-Chain Example:

{
  "199675": {
    "event": "issue",
    "issuerDid": "did:cardano:stake1u9...",
    "holderDid": "did:cardano:stake1ux...",
    "vcHash": "urn:uuid:550e8400-e29b-41d4-a716-446655440000",
    "vcType": "ContributionCredential",
    "vcFormat": "sd-jwt"
  }
}

vcHash Strategy

For SD-JWT credentials, vcHash uses the jti (JWT ID) claim to preserve selective disclosure. For Ed25519 credentials, vcHash is the SHA-256 hash of the canonicalized credential. See the Technical Specification for full details.

4. Transaction Structure

Typical DID Create Transaction

Inputs:
  - UTxO from wallet (payment address)

Outputs:
  - Change to wallet (minus fee)

Metadata:
  199674: {
    "id": "did:cardano:stake1u9...",
    "ipfs": "bafybeig...",
    "action": "create",
    "v": 1,
    "prev": null,
    "payloadSig": "{...}"
  }

Fee: ~0.17-0.25 ADA

Cost Analysis

Monthly Cost Estimate (100 DIDs, 500 VCs):

• DID operations: ~25 ADA
• VC operations: ~90 ADA
• Total: 115 ADA ($70 at$0.60/ADA)

5. Resolution Process

DID Resolution Algorithm

RESOLVE(did:cardano:stake1...)

1. Query Blockfrost for metadata label 199674
   GET /metadata/txs/labels/199674?order=asc

2. Filter events where metadata.id == did

3. Build event chain:
   - Start with create event (v=1, prev=null)
   - Link update events via prev → tx_hash
   - Check for revoke event

4. Verify each event:
   - Validate Ed25519 signature
   - Confirm stake address matches DID
   - Verify prev pointer chain

5. Return:
   - If revoked: { deactivated: true }
   - If valid: Latest DID Document from IPFS

Indexer Architecture

The indexer layer is split into global and forkable components:

DID Indexer (Global) – Single ecosystem-wide indexer for all did:cardano identities:

VC Indexer (Forkable) – Per-organization indexer for credential status:

Verifier Discovery Flow:

Verifiers resolve the issuer’s DID Document to find the appropriate VC Indexer:

1. Extract issuerDid from credential
2. GET /did/{issuerDid} → DID Document
3. Find service with type: "VCIndexer"
4. GET {serviceEndpoint}/vc/{vcHash}/status → revocation status

Fallback: If no VCIndexer service is present in the issuer’s DID Document, verifiers SHOULD default to the Prisma VC Indexer (L_VC) or treat revocation status as unknown.

Custom Label Governance:

Organizations MAY use their own CIP-10 label (e.g., L_ORG = 888888) or default to L_VC (199675). The issuer’s DID Document service field determines which indexer verifiers should query.

Warning: Organizations reusing L_VC without their own label MUST ensure their credential schemas are compatible with the base VCEventPayload structure to avoid collisions. Registering a dedicated label is RECOMMENDED for production deployments.

Implementation Structure:

The VC Indexer and VC Interface share a common schemas package (monorepo structure):

prisma-dids/
├── packages/
│   ├── schemas/        # Shared credential type definitions
│   └── sdk/            # Core SDK
└── apps/
    ├── did-indexer/    # Global DID Indexer (Prisma-operated)
    ├── vc-indexer/     # Forkable VC Indexer (per-organization)
    └── vc-interface/   # Forkable VC Frontend (per-organization)

When forking, organizations modify packages/schemas/ with their credential types, and both indexer and interface stay synchronized.

Implementation Status: The forkable VC Indexer architecture is implemented. Organizations deploy their own VC Indexer instances; see the VC Indexer Fork Guide.

6. Security Considerations

Threat Model

Signature Verification

All DID events are verified using:

1. Ed25519 signature over canonicalized payload (UTF-8 bytes)
2. Stake address derivation from signing address
3. Controller match between derived stake and DID identifier

async function verifyDIDEvent(event: DIDEvent): Promise<boolean> {
  // 1. Verify Ed25519 signature
  const validSig = await ed25519.verifyAsync(sig, message, pubKey);
  if (!validSig) return false;
 
  // 2. Derive stake address from signing address
  const stakeFromSigner = deriveStakeAddress(event.payloadSig.address);
 
  // 3. Compare with DID
  const stakeFromDid = event.id.replace('did:cardano:', '');
  return stakeFromSigner === stakeFromDid;
}

Dependencies

References

Cardano Improvement Proposals

• CIP-10: Transaction Metadata Label Registry 
• CIP-20: Transaction Message/Comment Metadata 
• CIP-30: Cardano dApp-Wallet Web Bridge 

W3C Standards

• DID Core 1.0 
• Verifiable Credentials Data Model 2.0 

IETF Standards

• SD-JWT (draft-ietf-oauth-selective-disclosure-jwt) 

Related Documentation

• Architecture - Component model (v1.6.2)
• Technical Specification - Full technical specification
• ADR: CIP-68 vs Metadata - Architecture decision record