Phala Cloud VRF

A Verifiable Random Function (VRF) implementation leveraging Trusted Execution Environment (TEE) technology on Phala Cloud and DStack. Delivers cryptographically verifiable randomness for Web3 applications with hardware-backed security and unprecedented efficiency.

Key Advantages 🚀

1. Cryptographically Verifiable Randomness

• TEE-Secured Computation: Every random output is signed by a TEE-protected private key and can be independently verified on-chain through signature.

2. Blazing Fast Performance

• Response as Flash: Our event-driven architecture and TEE-derived-key mechanism ensures 2-4 seconds latency end-to-end.

3. One-Click Deployment

• Phala Cloud Native: We already built the template. Visit the template to try it!

4. Production-Ready Infrastructure

• Mainnet-Proven: Audited implementation supporting Base Sepolia & Sepolia & Abstract testnets
• Live Demo: Video walkthrough demonstrating end-to-end workflow

The system comprises:

1. On-chain VRF Coordinator Contract
2. Off-chain VRF Generator (Confidential VM)
3. Client-facing API endpoints

VRF Workflow

1. Initial Setup

sequenceDiagram
    participant ContractOwner
    participant Contract
    participant Offchain-VRF
  
    Offchain-VRF->>Offchain-VRF: Randomly generates wallet keypair (wallet_sk, wallet_address)
    Offchain-VRF->>Offchain-VRF: TEE generates signing keypair (signing_sk, signing_pubkey)
    ContractOwner->>Offchain-VRF: GET /get_wallet
    Offchain-VRF->>ContractOwner: Return wallet_address
    ContractOwner->>Contract: setTrustedThirdParty(wallet_address)
    ContractOwner->>Offchain-VRF: GET /pubkey
    Offchain-VRF->>ContractOwner: Return signing_pubkey
    ContractOwner->>Contract: updateOfflinePublicKey(signing_pubkey)

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• Trusted Wallet Identity Establishment Offchain-VRF generates wallet_sk (private key) and derives wallet_address. Contract owner registers this address as trusted via setTrustedThirdParty(). And further transactions are sent from this wallet address.

• OffChain Key Distribution by TEE TEE generates separate signing_sk for VRF operations. Contract owner retrieves the corresponding public key via /pubkey endpoint and register it on-chain

2. Randomness Request Flow

sequenceDiagram
    participant User
    participant Contract
    participant Offchain-VRF
  
    User->>Contract: requestRandomNumber(seed)
    Contract->>Contract: Store request in queue
    Contract-->>Offchain-VRF: Emit RequestQueued(requestId, seed)
    Offchain-VRF->>Offchain-VRF: Listen for RequestQueued events
    Offchain-VRF->>Offchain-VRF: Compute random = VRF(signing_sk, seed)
    Offchain-VRF->>Offchain-VRF: Sign(requestId + seed + random)
    Offchain-VRF->>Contract: onRandomGenerated(requestId, random, signature)
    Contract->>Contract: Verify signature matches signing_pubkey
    Contract-->>Contract: Emit RandomFulfilled(requestId)

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• Request Initiation Users submit randomness requests with unique seeds via requestRandomNumber(seed)

• TEE Computation Offchain-VRF monitors events and processes queued requests using:

  random = SHA256(signing_sk + seed)
  signature = ethers.Wallet.signMessage(signing_sk, solidityPackedKeccak256(requestId, seed, random))

• On-chain Verification Contract verifies using ECDSA recovery:

  address recovered = ecrecover(hash, v, r, s);
  require(recovered == signing_pubkey, "Invalid signature");

Key Features

• TEE-Backed Security

  • Secure key generation & storage in enclave
  • Memory encryption and attestation proofs

• Verifiability

  • Cryptographic proof of correct computation
  • On-chain signature verification

• Fault Tolerance

  • Automatic request retries
  • Transaction nonce management

• Monitoring

  • Real-time request tracking via API
  • Event history inspection

API Endpoints

Endpoint	Method	Description
/get_wallet	GET	Returns TEE's operational wallet address
/pubkey	GET	Retrieves offline public key for VRF verification
/update-secretkey	GET	Optional protected key-rotation endpoint. Disabled unless UPDATE_SECRET_KEY_TOKEN is set; callers must provide x-update-secret-key-token.

Development Setup

Prerequisites

• Node.js ≥ 18.18
• Docker
• Phala Cloud account

1. Clone repository:

git clone https://github.com/your-org/phala-cloud-vrf.git
cd phala-cloud-vrf

2. Configure environment:

cp env.local.example .env.local
# Set an EVM RPC URL and deployed VRF coordinator contract address.
# Optional: set UPDATE_SECRET_KEY_TOKEN to enable protected HTTP key rotation.

3. Download and run TEE simulator:

wget https://github.com/Leechael/tappd-simulator/releases/download/v0.1.4/tappd-simulator-0.1.4-aarch64-apple-darwin.tgz
tar -xvf tappd-simulator-0.1.4-aarch64-apple-darwin.tgz
cd tappd-simulator-0.1.4-aarch64-apple-darwin
./tappd-simulator -l unix:/tmp/tappd.sock

4. Docker Compose:

docker-compose up

5. Run tests: Use the contract address and localhost:3000 and the random seed to run request.ts to test the VRF workflow.

Phala Cloud Deployment

Use docker-compose.yml to deploy on Phala Cloud. Set ENV RPC_URL and CONTRACT_ADDRESS to setup. Use a real EVM RPC URL for the target network and a valid deployed VRF coordinator contract address. The app validates these values at startup and exits with a clear error when they are missing or malformed.

The /update-secretkey endpoint changes the VRF signing key and should not be public. It is disabled by default. Only set UPDATE_SECRET_KEY_TOKEN if you need HTTP key rotation, and call the endpoint with the x-update-secret-key-token header. Then use contract address and container network ip and the random seed to run request.ts to test the VRF workflow.

You can also click the button below!

Demo Contract:

You can use the demo contract to test the VRF workflow. The contract is deployed on Base Sepolia testnet and Abstract testnent.

You can check the transactions and events on the testnet. The speed of the transactions is fast, it only costs 2 blocks to generate the random number. If you want to test the VRF workflow, you can follow the steps above both on local and on the phala cloud.

Also we have a workflow demo Video walkthrough