Connecting a USDT checkout with HMAC and webhooks

Integrating with CHINAUSDT comes down to two trust boundaries: how you create orders, and how we notify you that payment succeeded.

Create order: HMAC signing string

Checkout APIs (e.g. POST /checkout/v1/orders) require:

• X-ZLPay-Key
• X-ZLPay-Timestamp
• X-ZLPay-Nonce
• X-ZLPay-Signature

The signing string is exactly five lines:

METHOD
PATH
TIMESTAMP
NONCE
SHA256_HEX(RAW_BODY)

Sign with HMAC-SHA256 over that string using your project secret, then hex-encode. Hash the raw body bytes—never re-serialize JSON after parsing.

Timestamps + nonce stop replays; optional X-ZLPay-Idempotency-Key keeps one business intent to one order.

Notify: webhooks

After on-chain confirm and settlement, CHINAUSDT posts to your webhook_url (e.g. order.paid). You should:

1. Verify X-ZLPay-Signature with the webhook secret;
2. Fulfill idempotently by out_trade_no;
3. Return HTTP 2xx or we will retry with backoff.

Put business fields in notify_ref at create time; webhooks echo them back. The payment system does not understand membership semantics.

See the API page in the tenant console for live key material (secrets shown once at creation).