> For the complete documentation index, see [llms.txt](https://docs.coda.co/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.coda.co/codapay/direct-api-integration/direct-api-integration-for-cards/getting-started/how-to-generate-the-x-signature.md).

# How to generate the x-signature

For every charge request notification, the Coda system will carry out a verification process to ensure its integrity. Coda will compare the ***x-signature*** header in the request with the signature of the request body.\
\
If the signatures do not match, our system will reject the request and return error.\
\
This process is to ensure the integrity and security of our charge requests, reducing the risk of any payload being tampered.<br>

*Generating the signature*

The code snippet below is a sample code for generating signatures. Steps are also explained further below.

```java
public String generateSignature(@Nonull String requestTime, @Nonull String
requestBody, @Nonull String signingSecret) {
// Construct signature message
Coda Payments Pte. Ltd. Confidential
20
String message = String.format("%s.%s"
, requestTime, requestBody);
// using commons-codec:commons-codec:1.16.0 library
return new HmacUtils("HmacSHA512"
, signingSecret).hmacHex(message);
}
```

*Steps:*

1. Append the values listed below as a string as follows: *"{requestTime}.{requestBody}".*\
   *Example:*

```java
RequestTime = 1700486578888
RequestBody = {"type":"charge.status.succeeded","data":{"id":"evt_sg18c678ba5af0019"}}
String message =
"1700486578888.{"type":"charge.status.succeeded","data":{"id":"evt_sg18c678ba5af0019"}}"
```

2. Calculate the HMAC-SHA512 hash of the string using your signing secret as the key. The signing secret is a pre-shared key configured for your webhook endpoint. The HMAC-SHA512 algorithm will return a byte array value.

   *Example:*

```java
SigningSecret = "BbCVjTu59yVUMMon8mgN9C37piCGfijN"
```

3. Convert the byte array value to a hexadecimal string. The result will be like:

   "a0c2d905877e9282a3954743f918f98f991c144020c535458c84767b6e146cf8cad4433accc2047258f6d5c4be07264596cfc58cfeea9e8551090f26e828e6bd"

*Verifying the Signature*

1. Extract the X-Request-Time and X-Signature headers from the webhook request
2. Get the raw request body as a string (before any parsing)
3. Generate the expected signature following Steps 1-3 above
4. Compare the generated signature with the X-Signature header value using a constant-time comparison
5. Verify that the X-Request-Time is within an acceptable time window (e.g., within last 5 minutes) to prevent replay attacks


---

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