# 3. Callback To Merchant Portal

### CallBack/ Response URL

```
<YourCallBackURL>?trackid=xxxx&result=xxxx&refid=&errormessage=&Hash=xxxx
```

### **Call Back Response Parameters**

| **Parameters**  | Data Type | Description                                                                             |
| --------------- | --------- | --------------------------------------------------------------------------------------- |
| `trackid`       | string    | Reference ID passed in the request.                                                     |
| `result`        | string    | <p>Payment result.<br>Example: CAPTURED, NOT CAPTURED, DECLINED, REJECTED, BLOCKED.</p> |
| `refid`         | string    | Payment Reference Number.                                                               |
| `error message` | string    | If result is other than CAPTURED, then it gives you the actual reason.                  |
| `hash`          | string    | Use this for integrity of the data explained in response integrity section              |

### How to identify parameters that are tampered?

If you want to check whether the parameters tamper or not, convert below parameters into a hash and compare with your hash which you got as a response in a query string.

Use the below method to identify parameter tempering. &#x20;

```
  String outParams = $"trackid={trackid}&result={result}&refid={refid}";
  String outhashValue = GetHashValue(outParams,_key);
  if (Hash != outhashValue)
  {
  //This means it is tampered
  // Your code
  }
  else{
  }
```


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