Circle Payment Network (CPN) Integration

This guide covers how to integrate Knit's Managed Signing API with Circle's Payment Network (CPN) for seamless payment processing.

What is CPN?

Circle Payment Network (CPN) is Circle's payment infrastructure that enables fast, low-cost USDC transfers. CPN V2 uses EIP-712 signatures (Permit2) for gasless payment authorization, while CPN V1 uses traditional on-chain transactions.

Why Use Knit for CPN?

• Secure Key Management: Your signing keys are securely managed by Knit
• Policy Controls: Define granular rules for what can be signed
• Simplified Integration: Single API for wallet creation, policy management, and signing
• Audit Trail: Complete visibility into all signing operations

CPN Versions

Integration Flow

1. Create Wallet     → POST /managed-signing/wallets
2. Create Policy     → POST /managed-signing/policies
3. Permit2 Approval  → POST /managed-signing/requests (one-time, on-chain)
4. Per-Payment Sign  → POST /managed-signing/requests (per payment, off-chain)

Quick Links

• Onboarding Checklist - Complete setup guide
• Create Wallet - Step 1: Create a CPN-enabled wallet
• Create Policy - Step 2: Configure CPN policy rules
• Permit2 Approval - Step 3: One-time on-chain approval
• Per-Payment Signature - Step 4: Sign each payment
• Troubleshooting - Common issues and solutions

Supported Networks

CPN is typically used on:

• MATIC_MAINNET (Polygon)
• ETHEREUM_MAINNET

Prerequisites

Before integrating:

1. Create an OAuth client and obtain an access token — see Authentication
2. Allow-list your server IP addresses in the dashboard
3. Get the USDC token address for your target network
4. Get the Permit2 contract address for your target network