---
title: Human checkout with the Payments SDK
description: Create signed Curvy payment requests, publish signers, and confirm payments on your shop.
---

# Human checkout

Curvy hosts the **payment page**. Your shop creates a signed deposit request (without a recovery address), redirects the buyer to Curvy, and confirms the payment with `verifyPayment` using the attempt’s **payment reference**.

## Keys

| Material | Where | Purpose |
| --- | --- | --- |
| Spending / viewing keys | Offline | Later spend of your Curvy balance — never on the shop |
| Public `S`, `V`, BabyJubjub | Shop backend | Derive one-time payment destinations |
| Request signing key (secp256k1) | Shop backend | Sign the checkout payload |
| Signer address list | `/.well-known/curvy-payments.json` | Let Curvy verify the signature |

A breach of public receiving keys plus the request signing key can mint fraudulent **links to you**. It cannot steal your shielded balance or redirect an existing payment.

## Creating a payment

```ts
import { initialize } from "@0xcurvy/payments-sdk/merchant";
import { signPaymentIntent } from "@0xcurvy/payments-sdk/intent";
import { buildCheckoutUrl } from "@0xcurvy/payments-sdk/transport";

const sdk = initialize({
  recipient: {
    S: process.env.CURVY_PUBLIC_S!,
    V: process.env.CURVY_PUBLIC_V!,
    babyJubjubPublicKey: process.env.CURVY_PUBLIC_BABYJUBJUB!,
  },
  chainId,
  merchantOrigin: "https://shop.example",
  confirmations: 12,
  ttlSeconds: 600,
});

const request = await sdk.createPaymentRequest({
  amount: orderTotal,
  token: usdcAddress,
});

const signed = await signPaymentIntent(request, (typedData) =>
  yourSigner.signTypedData(typedData),
);

const checkoutUrl = buildCheckoutUrl(CURVY_CHECKOUT_ORIGIN, signed);
```

Store the payment reference (`ephemeralKeyX`, `ephemeralKeyY`) when you create the request — for example in your database or in an httpOnly session cookie, whichever fits your stack. Do not put your payment reference in the signed checkout package.

## Confirming a payment

After checkout, the customer is redirected to `{merchantOrigin}{checkoutCompletePath}#txHash=…`. Call `verifyPayment` with the stored payment reference and the hash from the URL fragment:

```ts
const confirmed = await sdk.verifyPayment({
  publicClient,
  aggregatorAddress: CURVY_AGGREGATOR,
  ephemeralKey: [ephemeralKeyX, ephemeralKeyY],
  txHash: shieldTxHash,
});
```

See [Confirming payments](./confirming-payments) for optional `txHash` omission and retry guidance.

## Publishing your signing keys

Serve this from your origin (CORS `*`, short cache):

```http
GET https://shop.example/.well-known/curvy-payments.json
Access-Control-Allow-Origin: *
Cache-Control: public, max-age=60
```

```json
{
  "version": 1,
  "signers": [
    {
      "address": "0xYourSignerAddress",
      "alg": "eip712-secp256k1",
      "notAfter": "2027-01-01T00:00:00.000Z"
    }
  ]
}
```

Build the document with `buildMerchantKeySet` from `@0xcurvy/payments-sdk/merchant/keys`.

## What you sign

EIP-712 domain name `"Curvy Payments"`, version `"1"`. If `checkoutCompletePath` is omitted from input, it defaults to `/checkout/complete` and is **always** present in the typed data.

| Field | Meaning |
| --- | --- |
| `ephemeralKeyX` / `ephemeralKeyY` | **Payment reference** — the on-chain identity for this attempt |
| `token` | Asset the customer must send |
| `amount` | Exact amount (token units) |
| `chainId` | Network |
| `ownerHash` | Binds the portal destination to your identity |
| `viewTag` | Protocol discovery aid |
| `merchantOrigin` | Your origin for the return |
| `checkoutCompletePath` | Absolute path on that origin (optional; default `/checkout/complete`) |
| `expiry` | Unix seconds |

No `recovery` and no `paymentId`. Recovery is chosen on Curvy’s page (connected wallet by default).

## Return URL

After a successful shield, checkout navigates top-level to:

```
{merchantOrigin}{checkoutCompletePath}#txHash=<shield tx>
```

| Piece | Value |
| --- | --- |
| Origin | Signed `merchantOrigin` |
| Path | Signed `checkoutCompletePath`, or `/checkout/complete` |
| Query | Empty |
| Fragment | `txHash=` plus the **shield** hash (not the customer’s transfer) |

The hash is a hint. Confirm with `verifyPayment` on your server — see [Confirming payments](./confirming-payments).

## Related

- [Getting started](./getting-started)
- [Confirming payments](./confirming-payments)
- [Accepting payments for businesses](/for-businesses/accepting-payments)