VOPRF Server

A VOPRF (Verifiable Oblivious Pseudorandom Function) server implementation built with TypeScript, Express.js, and Node.js.

This server implements the VOPRF protocol as defined in RFC 9497 using the Cloudflare VOPRF-TS library.

Setup

1. Install dependencies:

   npm install

2. Create a .env file (optional):

   PORT=8001
   IP=127.0.0.1
   SERVICE_NAME=voprf-server
   NODE_ENV=development

Development

• Start development server (with hot reload):

  npm run dev

• Build the project:

  npm run build

• Start production server:

  npm start

Code Quality

• Lint code:

  npm run lint

• Fix linting issues:

  npm run lint:fix

• Format code:

  npm run format

• Check formatting:

  npm run format:check

API Endpoints

General

• GET /ping - Health check endpoint that returns {"reply": "pong"}

VOPRF Endpoints

• GET /voprf/public-key - Get the server's public key for VOPRF verification
• POST /voprf/evaluate - Perform blind evaluation of client requests

VOPRF Usage

Get Public Key

curl http://localhost:8001/voprf/public-key

Response:

{
  "publicKey": "base64-encoded-public-key",
  "suite": "P384-SHA384"
}

Blind Evaluation

curl -X POST http://localhost:8001/voprf/evaluate \
  -H "Content-Type: application/json" \
  -d '{"evaluationRequest": "base64-encoded-evaluation-request"}'

Client Example

Run the included client example to see the full VOPRF protocol in action:

# Start the server in one terminal
npm run dev

# Run the client example in another terminal
npm run example:client

Project Structure

src/
├── index.ts        # Application entry point
├── app.ts          # Express app configuration
├── config/
│   └── index.ts    # Environment configuration
└── voprf/
    └── routes.ts   # VOPRF server endpoints and logic

examples/
└── voprf-client.ts # Example VOPRF client implementation

VOPRF Protocol

The VOPRF (Verifiable Oblivious Pseudorandom Function) protocol allows a client to obtain pseudorandom function evaluations from a server without revealing the input to the server. The server cannot learn the client's input, and the client can verify that the server used the correct private key.

Protocol Flow:

1. Client requests server's public key
2. Client blinds their input and sends an evaluation request
3. Server performs blind evaluation and returns the result
4. Client unblinds the result to get the final PRF output

This implementation uses the P384-SHA384 suite for cryptographic operations.