TrackBack Agent SDK

• Create, Revoke, Resolve, Update DIDs
• Connects with TrackBack chain
• Store DID documents in a Decentralised file store ( IPFS for MVP stage)
• This is a part of SDKs for Verifiable Credentials, Verifiable Credential Presentations, DID Keys, Self Sovereign Identity and Decentralised Identifiers

IMPORTANT!

• This is a minimum viable product suite with limited functionality.
• Do not use this for productionise code or for an end product
• Please view Limitations

Architecture

TrackBack Agent

Limitations

The following features are not available in this minimum viable SDK

• Zero Knowledge Proofs
• Batch insert / update of DIDs
• DID revocation - the DID document will be available on IPFS without DID meta information
• Support for JSON-LD
• Single Sign On (using Self Sovereign Identity)
• Saving a cryptographical print of a verifiable credential on chain
• Multiple authentication
• DID delegation is incomplete , only the nominated parties can modify a DID document
• DID delegation functionality over a verifiable credential will be delivered after MVP stage

Miscellaneous

• You may see warning messages when creating DIDs
• Only works with already created accounts on chain

Issue and Verify credentials

Requirements

• Install nodejs 14.0.0 or above.
• Install follwoing dependencies.

sudo npm i -g ts-node
npm install -g typescript
nvm use 14
npm install @trackback/agent

Constructing SSI Elements

import {CredentialIssuer,Connector, createAccount, TrackBackAgent} from '@trackback/agent';

async function createAnIssuer() {
  // Create a Connector object.
  const connector = new Connector();

  // Initialise the `TrackBackAgent` with a connector instance.
  const agent = new TrackBackAgent(connector);
  
  // An Issuer needs an active account on TrackBack Blockchain
  // Please use the default account for this MVP release
  // Functionality will be added to create ad use your own objects in future releases.
  const account = await connector.getDefaultAccount();

  // A valid context is required to persist an object to the chain 
  const context = {
      agent,
      account: account
  }

  // Creates an issuer
  const issuer = await CredentialIssuer.build();

  // Saves a DID Document
  await issuer.save(context, {"didDocumentMetadata": "docMeta"}, {"didResolutionMetadata": "resolutionMeta"});

  let resolevedDIDDocument = await agent.procedure.resolve(issuer.toDidDocument().id);
  /**  resolevedDIDDocument
   * {
          did_resolution_metadata: { hello: 'resolutionMeta' },
          did_document_metadata: { hello: 'docMeta' },
          block_number: 218812,
          block_time_stamp: 1635477636,
          updated_timestamp: 1635477636,
          did_ref: 'https://ipfs.trackback.dev:8080/ipfs/QmdH3JyxJ1A45goKAt18ja3TX67ea4Vz2NTyLkLXEQYTk8',
          sender_account_id: '5GrwvaEF5zXb26Fz9rcQpDWS57CtERHpNehXCPcNoHGKutQY',
          public_keys: [ '5GrwvaEF5zXb26Fz9rcQpDWS57CtERHpNehXCPcNoHGKutQY' ],
          did_document: {
              '@context': [ 'https://www.w3.org/ns/did/v1' ],
              id: 'did:trackback:e97aaebd-c221-44d6-925f-f73493eec3dd',
              verificationMethod: [ [Object] ]
          }
          }
          {
          header: {
              alg: 'EdDSA',
              typ: 'JWT',
              kid: 'did:trackback:key:JsonWebKey2020:ZpM9EIlXv2Yj9F1IaIS-S1-BkSrXIq8ad2rpAffDDlg#ZpM9EIlXv2Yj9F1IaIS-S1-BkSrXIq8ad2rpAffDDlg'
          },
          payload: {
              nbf: 1635477651,
              iss: 'did:trackback:e97aaebd-c221-44d6-925f-f73493eec3dd',
              vp: {
              '@context': [Array],
              type: [Array],
              verifiableCredential: [Array]
              }
          },
          signature: 'PdPWI_J88vokw68_APAFh3BU7Go6grabOGj3SAtFbfOwpJCz0yyAh7xR7rdZIw7lhCHwPfB6-25QFYsUEehACw'
          }
   * */
}

import {CredentialIssuer,Connector, createAccount, TrackBackAgent} from '@trackback/agent';

async function verifiableCredential(credentialData: any) {


  const connector = new Connector();
  const agent = new TrackBackAgent(connector);
  
  const account = await connector.getDefaultAccount();

  const context = {
      agent,
      account: account
      }
  const issuer = await CredentialIssuer.build();
  await issuer.save(context, {"hello": "docMeta"}, {"hello": "resolutionMeta"});

  /*
  Ppopulate Credential subject with data
  Reference :- https://www.w3.org/TR/vc-data-model/#example-1-a-simple-example-of-a-verifiable-credential
  "credentialSubject": {
      
      "id": "did:example:ebfeb1f712ebc6f1c276e12ec21",
      
      "alumniOf": {
      "id": "did:example:c276e12ec21ebfeb1f712ebc6f1",
      "name": [{
          "value": "Example University",
          "lang": "en"
      }, {
          "value": "Exemple d'Université",
          "lang": "fr"
      }]
      }
  },
  
  */
  const credential = {
      '@context': ['https://www.w3.org/2018/credentials/v1'],
      type: ['VerifiableCredential'],
      issuanceDate: '2010-01-01T19:23:24Z',
      credentialSubject: credentialData, // default {}
      issuer: issuer.id,
  };

  // Creates a JWT
  const jwt = await issuer.createVerifiableCredentials(credential);

  // Creates a JWT presentation
  const jwtPresentation = await issuer.createVerifiablePresentation([jwt], issuer.keypair);

  let decode = CredentialVerifier.decodeJWT(jwtPresentation);

  // Prints decoded JWT presentation
  console.log(decode);
}

/*
IssuerA Creates a Credential
*/
async function createCredentials() {
  
  // Creates a connector object
  const connector = new Connector();
  // Creates the TrackBack Agent
  const agent = new TrackBackAgent(connector);
  
  // Creates the defualt account for the issuer
  // `Alice` if there's no mnemonic
  // The passing mnemonic must be a valid account on TrackBack
  // For the MVP please use either Alice or Bob since we are finalising our token
  // economic and account model
  const account = await connector.getDefaultAccount();

  // Creates the issuer's context
  const context = {
      agent,
      account: account
  }

  // Create Issuer's keypair
  const IsserA = await CredentialIssuer.build();
  // Saves the Issuer's DID
  // This needs to be done only once per issuer
  // Do not create new issuers per credentials
  await IsserA.save(context, {"hello": "docMeta"}, {"hello": "resolutionMeta"});
  
  // Issuer creates a credential
  // Pass teh required data as JSON to `credentialSubject: {},`
  const credential = {
      '@context': ['https://www.w3.org/2018/credentials/v1'],
      type: ['VerifiableCredential'],
      issuanceDate: '2010-01-01T19:23:24Z',
      credentialSubject: {},
      issuer: IsserA.id,
  };
  const jwt = await IsserA.createVerifiableCredentials(credential);
  
  // Issuer creates a verifiable credential presentation 
  const jwtPresentation = await IsserA.createVerifiablePresentation([jwt], IsserA.keypair);

  // The above jwtPresentation can reside on a wallet / website or in a database

A verifier verifies the JWT

async function verify(jwtPresentation) {
  // Creates a connector object
  const connector = new Connector();
  // Creates the TrackBack Agent
  const agent = new TrackBackAgent(connector);
   // Create a verifier
  let verifier = new CredentialVerifier();

  // For the MVP please use an Account available on TrackBack Chain.
  const accountB = await connector.getDefaultAccount("Bob");
  const verifierContext = {
      agent,
      account: accountB
  }

  const r = await verifier.verifyPresentation(jwtPresentation, verifierContext);
  console.log(r); // True | False
}

Usage

Installation

npm install @trackback/agent

## or yarn 
yarn add @trackback/agent

Importing

ES Modules import

import { TrackBackAgent } from '@trackback/agent'

CommonJS import

const { TrackBackAgent } = require('@trackback/agent');

DID Operations

• Reference :- https://www.w3.org/TR/did-core/

Create a DID

• The DID Document must be saved on IPFS

/*
* `saveToDistributedStorage returns the `cid`
* Please Include this value as the didRef when calling the constructDIDDocument and updateDIDDocument methods.
*/
agent = new TrackBackAgent(new Connection());
let result = await agent.procedure.saveToDistributedStorage(desDIDStructure, null);

/*
* Returns Promise<ExtrinsicResults>
* ExtrinsicResults 
export type ExtrinsicResults = {
  [key: string]: any;
} | null;
*/
let agent = new TrackBackAgent(new Connector());
await agent.procedure.constructDIDDocument(
    account,
    didDocument,
    didDocumentMetadata,
    didResolutionMetadata,
    didRef,
    publicKeys
);

Resolve a DID

let did_uri = "did:0xfac17a:0x68b5d6033f8958558cc0bb48328bb9ba0651078b3f69eee533a2dfdba75965f2"
let agent = new TrackBackAgent(new Connector());
await agent.procedure.resolve(did_uri);

Revoke a DID

/*
* Returns Promise<ExtrinsicResults>
* ExtrinsicResults 
export type ExtrinsicResults = {
  [key: string]: any;
} | null;
*/
let did_uri = "did:0xfac17a:0x68b5d6033f8958558cc0bb48328bb9ba0651078b3f69eee533a2dfdba75965f2"
let agent = new TrackBackAgent(new Connector());
await agent.procedure.revoke(
    account,
    did_uri
);

Update a DID

• To update a DID Document, you need to grab the DID information and meta data from resove method

let did_uri = "did:0xfac17a:0x68b5d6033f8958558cc0bb48328bb9ba0651078b3f69eee533a2dfdba75965f2"
let agent = new TrackBackAgent(new Connector());
await agent.procedure.resolve(did_uri);

/*
* Returns Promise<ExtrinsicResults>
* ExtrinsicResults 
export type ExtrinsicResults = {
  [key: string]: any;
} | null;
*/
let agent = new TrackBackAgent(new Connector());
await agent.procedure.updateDIDDocument(
    account,
    didDocument,
    didDocumentMetadata,
    didResolutionMetadata,
    didRef,
    publicKeys
);

Create W3C Verifiable Credentials

Following steups to create and sign W3C credential as jwt

Sign credentials

import { CredentialIssuer } from '@trackback/agent'
import { createAccount } from '@trackback/agent/account'

const connector = new Connector();
// initialize the agent
const agent = new TrackBackAgent(connector);

const account = connector.getAccount(mnemonic)

// create context
const context = {
  agent,
  account
}


//initialize credential issuer
const issuer = await CredentialIssuer.build();

// save did document to ipfs
issuer.save(context)

const credential = {
              '@context': ['https://www.w3.org/2018/credentials/v1'],
              type: ['VerifiableCredential'],
              issuanceDate: '2010-01-01T19:23:24Z',
              credentialSubject: {},
              issuer: issuer.id,
          };

const jwtCredential = await issuer.createVerifiableCredentials(credential)

// jwt

Verify credentials

const connector = new Connector();
// initialize the agent
const agent = new TrackBackAgent(connector);

const account = connector.getAccount(mnemonic)

// create context
const context = {
  agent,
  account
}

const verifier = new CredentialVerifier();

// ... create jwtCredential


 const r = await verifier.verifyCredentials(jwtCredential, context);


 // true/false

Create W3C Verifiable Presentation

Sign presentation

Following steups to create and sign W3C Presentation as jwt

import { CredentialIssuer } from '@trackback/agent'
import { createAccount } from '@trackback/agent/account'


//initialize credential issuer
const issuer = await CredentialIssuer.build();

const keyPair = issuer.keypair

const jwtPresentaion = await issuer.createVerifiablePresentation([
  jwtCredential
], keyPair)

// jwt

Verify presentation

Context is require to retrive verification for credentials

const connector = new Connector();
// initialize the agent
const agent = new TrackBackAgent(connector);

const account = connector.getAccount(mnemonic)

// create context
const context = {
  agent,
  account
}

const verifier = new CredentialVerifier();

// ... create jwtPresentation


 const r = await verifier.verifyPresentation(jwtPresentation, context, issuer.keypair)

 // true/false

With custom chain settings

You can use custom url with sdk.

More info on options : https://polkadot.js.org/docs/api/start/rpc.custom

const { DefaultOptions } = require('@trackback/agent')
const options = {
  url: 'ws://custom.node.example.com', // custom node url ws[s]://custom.node.example.com[:9944]
  options: {...DefaultOptions.options} // using trackback defaults
}

const agent = new TrackBackAgent(new Connector(options));

Creates a new Account

// CREATE NEW ACCOUNT

const connector = new Connector();
const account = connector.createAccount({name:"TrackBack"});

// {
//     keyPair:... ,
//     mnemonic: ... // Your secret key
// }

// use polka js wallet to send credit to your account
// Creates the new account by using the mnemonic generated for the new account
// You can use a design implementation of your own to store the mnemonic
// https://polkadot.js.org/apps/?rpc=wss%3A%2F%2Falpha-node.trackback.dev#/accounts

// initialize the agent
const agent = new TrackBackAgent(connector);

// load your account back
const importedAccount = connector.getAccount(account.mnemonic)

// create context
const context = {
  agent,
  account: importedAccount
}


// Creates an Issuer
const issuer = await CredentialIssuer.build();

const metada = { "content-type": "application/json" }
const resMetada = { "content-type": "application/json" }

// Creates a Transaction based on the new account 
const result = await issuer.save(context, metada, resMetada);