JazzCash, EasyPaisa and Stripe behind one API

Pakistani gateways each want a different payload, signed a different way. pk-pay gives you one function call — and checks the callback is genuine when the money comes back.

npm i pk-pay TypeScript · MIT · Express, Fastify & Next.js helpers

1. One call, any gateway

Swap the provider and nothing else changes. You get back a form to send the customer to.

const payment = await pay.createPayment({
  provider: 'jazzcash',   // or 'easypaisa'
  amount: 250000,
  currency: 'PKR',
  returnUrl: 'https://shop.pk/callback',
  customerPhone: '03001234567',
});

res.send(payment.redirectForm);

Try it

2. Amounts are whole numbers

Money is passed in paisa — the smallest unit — so a rounding error can never cost someone a rupee. JazzCash takes paisa directly; the SDK reformats it for gateways that want something else.

// 250000 paisa = PKR 2,500.00
amount: 250000

// never this:
// amount: 2500.00  ← floats and money
//                   don't mix

Try it Amount in paisa

customer is chargedPKR 2,500.00

3. The request is signed for you

Each gateway wants its fields sorted, joined and hashed with your secret salt. Get the order wrong and the gateway rejects the payment. The SDK builds it; you never touch the crypto.

createClient({
  jazzcash: {
    merchantId,
    integritySalt,   // ← the signing key
  }
});

// pk_SecureHash is computed and attached
// HMAC-SHA256, uppercase hex

Live — real HMAC-SHA256

Integrity salt

Signature attached to the form

computing…

Change the salt or the amount above — the signature changes completely.

4. Callbacks get verified

When the gateway posts back, anyone could have sent that request. verifyWebhook recomputes the hash and throws if it doesn't match — so a forged "payment succeeded" never reaches your order code.

app.post('/callback', async (req, res) => {
  const event =
    await pay.verifyWebhook('jazzcash', req.body);

  // only runs if the signature is genuine
  markOrderPaid(event.transactionId);
});

Try tampering

pp_TxnRefNo

pp_Amount

pp_ResponseCode

signature valid

Raise the amount and watch it fail — the gateway signed the original numbers.