Wallet authentication

CIP-30 flow

1. The frontend connects a wallet and gets the payment address and key hash.
2. The backend creates a nonce-bound challenge.
3. The wallet signs the exact challenge payload with signData.
4. The backend verifies:
   • address network
   • payment key hash
   • challenge binding
   • expiry and one-time use
   • signature
5. The backend creates a session or applies the authenticated action.

Rules

• Only payment-key addresses are accepted.
• Never ask for a seed phrase or private key.
• Bind the payload to the intended host, purpose, address and key hash.
• Use one-time challenges and expiry.