This example demonstrates how to create a simple Express.js backend that works with the Reclaim Protocol. The backend will handle generating the configuration for the SDK and receiving proofs.

Backend Example

This example demonstrates how to create a simple backend that works with the Reclaim Protocol. The backend will handle generating the configuration for the SDK and receiving proofs.

Step-by-Step Implementation

1. Set up the project

First, create a new directory for your backend project and initialize it:

mkdir reclaim-backend-demo
cd reclaim-backend-demo
npm init -y
npm install express @reclaimprotocol/js-sdk

2. Create the server file

Create a new file named server.js and add the following code:

const express = require('express')
const { ReclaimProofRequest, verifyProof } = require('@reclaimprotocol/js-sdk')
 
const app = express()
const port = 3000
 
app.use(express.json())
app.use(express.text({ type: '*/*', limit: '50mb' })) // This is to parse the urlencoded proof object that is returned to the callback url
 
// Route to generate SDK configuration
app.get('/reclaim/generate-config', async (req, res) => {
  const APP_ID = 'YOUR_APPLICATION_ID'
  const APP_SECRET = 'YOUR_APPLICATION_SECRET'
  const PROVIDER_ID = 'YOUR_PROVIDER_ID'
 
  try {
    const reclaimProofRequest = await ReclaimProofRequest.init(APP_ID, APP_SECRET, PROVIDER_ID)
    
    reclaimProofRequest.setAppCallbackUrl('https://your-backend.com/receive-proofs')
    
    const reclaimProofRequestConfig = reclaimProofRequest.toJsonString()
 
    return res.json({ reclaimProofRequestConfig })
  } catch (error) {
    console.error('Error generating request config:', error)
    return res.status(500).json({ error: 'Failed to generate request config' })
  }
})
 
// Route to receive proofs
app.post('/receive-proofs', async (req, res) => {
  // decode the urlencoded proof object
  const decodedBody = decodeURIComponent(req.body);
  const proof = JSON.parse(decodedBody);
 
  // Verify the proof using the SDK verifyProof function
  const result = await verifyProof(proof)
  if (!result) {
    return res.status(400).json({ error: 'Invalid proofs data' });
  }
 
  console.log('Received proofs:', proof)
  // Process the proofs here
  return res.sendStatus(200)
})
 
app.listen(port, () => {
  console.log(`Server running at http://localhost:${port}`)
})

Do not use the express.urlencoded() middleware as it will conflict with the express.text() middleware above. The proof object sent to the callback URL needs to be parsed as text, otherwise it won't be processed correctly.

For detailed information about the proof object received in the /receive-proofs endpoint, refer to the Advance Configuration Proof Structure section.

3. Run the server

Start your Express server:

node server.js

Understanding the `reclaimProofRequestConfig`

The reclaimProofRequestConfig is a JSON string that contains all the necessary information for initializing the Reclaim SDK on the client-side. Here's an example of what the response from the /reclaim/generate-config endpoint might look like:

{
  "reclaimProofRequestConfig": "{
    \"applicationId\": \"<APPLICATION_ID>\",
    \"providerId\": \"<PROVIDER_ID>\",
    \"sessionId\": \"<SESSION_ID>\",
    \"context\": {
      \"contextAddress\": \"<CONTEXT_ADDRESS>\",
      \"contextMessage\": \"<CONTEXT_MESSAGE>\"
    },
    \"requestedProof\": {
      \"url\": \"<PROOF_URL>\",
      \"parameters\": {
        \"<PARAM1>\": \"\",
        \"<PARAM2>\": \"\"
      }
    },
    \"appCallbackUrl\": \"<CALLBACK_URL>\",
    \"signature\": \"<SIGNATURE>\",
    \"timeStamp\": \"<TIMESTAMP>\"
  }"
}

Let's break down the structure of the reclaimProofRequestConfig:

applicationId: Your unique application identifier.
providerId: The ID of the provider you're using.
sessionId: A unique identifier for this particular proof request session.
context:
- contextAddress: The address associated with the context (often set to "0x0").
- contextMessage: A custom message providing context for the proof request.
requestedProof:
- url: The URL from which the proof will be generated.
- parameters: Key-value pairs of parameters required for the proof.
appCallbackUrl: The URL where the proofs will be sent after generation.
signature: A cryptographic signature ensuring the integrity of the request.
timeStamp: The timestamp when the configuration was generated.

When you receive this response from your backend, you'll need to use the reclaimProofRequestConfig string to initialize the Reclaim SDK in your client application.

Using the Configuration in Client Applications

You can use this configuration to initialize the Reclaim SDK in various client platforms:

By using this approach, you keep sensitive information like your APP_SECRET on the server-side while still allowing your client applications to utilize all the SDK features securely.

Example