> ## Documentation Index
> Fetch the complete documentation index at: https://devzone.nayax.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Authentication

To ensure secure communication, every request sent by the Integrator must include two specific authentication headers. These headers verify your identity and ensure the integrity of the transaction data.

## Prerequisites

Before you begin, ensure you have the following resources:

* A valid Sign Key (shared by Nayax, typically 16 characters)
* The associated Sign Key ID

<Warning>
  Your request body must contain the `SparkTransactionId` field.
</Warning>

## Authenticate Requests

Once you have the required resources, you can start authenticating your API requests to Spark by following the steps below:

1. Combine the static string `IntegratorId` with your ID in the following format `IntegratorId: {SignKeyID}`. See the example below:
   ```
   IntegratorId: 927
   ```
2. Join the `SparkTransactionId` from your request body with your `Sign Key`, separated by a semicolon (`;`), in the following format: `SparkTransactionId;SignKey`
   ```
   123456789123456789abcdefghijklmnopqr;RbtdDsiVNjkAeRty
   ```
3. Perform a **SHA-256** hash on the resulting string using **UTF-8** encoding. Resulting hash:
   ```
   1b7dd1c4010698824de66f13e1387efc28a4bba00b720d4be8cdb3b598b9603e
   ```
4. The final header should look like the following:
   ```
   TransactionSignature: 1b7dd1c4010698824de66f13e1387efc28a4bba00b720d4be8cdb3b598b9603e
   ```

## Request Example (cURL)

See an example request for the `/StartAuthentication` endpoint:

<Note>
  **Base URL and Domain**

  The Spark API base URL is `https://{domain}/api`, where `{domain}` is your Nayax-assigned hostname. Nayax provides a QA domain during sandbox setup and a production domain after certification. Contact your Nayax integration engineer if you have not received your domain.
</Note>

```bash theme={null}
curl --location 'https://{your-domain}/api/StartAuthentication' \
--header 'IntegratorId: 927' \
--header 'TransactionSignature: 1b7dd1c4010698824de66f13e1387efc28a4bba00b720d4be8cdb3b598b9603e' \
--header 'Content-Type: application/json' \
--data '{
 "TokenId": 116383,
 "TerminalId": "0434334921100366",
 "TerminalIdType": 1,
 "Random": "123456789qwertyui",
 "Cipher": "X305dITNTAw2vHsxE+taVcn6UvgBC3fdI6QbqeABgHbo8CKsoZhqISJfslehCiA+L7XYrqvKFci7C6BNj/tr zBuNJwBEjgBzKhhgpJ5ggnw=",
 "SparkTransactionId": "123456789123456789abcdefghijklmnopqr"
}'
```

## See Also

<CardGroup cols={2}>
  <Card icon="bolt" title="Interactive Authentication Tool" href="/docs/integrate-pos-device/spark/security-authentication/spark-auth-tool">
    Build and inspect ciphers and signature headers in your browser, no code required.
  </Card>

  <Card icon="repeat" title="Payment Flows" href="/docs/integrate-pos-device/spark/payment-flows/transaction-flows-spark">
    How authentication fits into the full Spark transaction sequence.
  </Card>
</CardGroup>