Webhook Version V1

<?php
  $data = $_POST;
  $signature = $_POST["signature"];
  unset($data["signature"]); // $data now has all the POST parameters except signature
  ksort($data); // Sort the $data array based on keys
  $postData = "";
  foreach ($data as $key => $value){
    if (strlen($value) > 0) {
      $postData .= $value;
    }
  }
  $hash_hmac = hash_hmac('sha256', $postData, $clientSecret, true) ;
  
  // Use the clientSecret from the oldest active Key Pair.
  $computedSignature = base64_encode($hash_hmac);
  if ($signature == $computedSignature) {
    // Proceed based on $event
  } else {
    // Reject this call
  }
?>

import java.util.LinkedHashMap;
import java.util.Map;
import java.util.stream.Collectors;

import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;
import javax.crypto.spec.SecretKeySpec;
import javax.crypto.Mac;
import org.apache.commons.codec.binary.Base64;

public class ComputedSignature {

    public static boolean checkSignature(String clientSecret, String data) {

// write your code here
ObjectMapper objectMapper = new ObjectMapper();
String signatureKey = "signature";
String hash = "";
try {
Map<String, Object> jsonMap = objectMapper.readValue(data, new TypeReference<Map<String, Object>>(){});
String signature = jsonMap.get(signatureKey).toString();

            // remove the signature from map
            jsonMap.remove(signatureKey);
             Map<String, Object> sortedMap =  jsonMap.entrySet().
                     stream().
                     sorted(Map.Entry.comparingByKey()).
                     collect(Collectors.toMap(
                             Map.Entry::getKey,
                             Map.Entry::getValue,
                             (oldValue, newValue) -> oldValue, LinkedHashMap::new
                     ));

             // sort the map based on keys
             String postDataString = sortedMap.keySet().stream().map(key -> sortedMap.get(key).toString()).collect(Collectors.joining());

             // encode the post data on sha256
             Mac sha256HMAC = Mac.getInstance("HmacSHA256");
             SecretKeySpec secretKey  = new SecretKeySpec(clientSecret.getBytes(), "HmacSHA256");
             sha256HMAC.init(secretKey);

             hash = Base64.encodeBase64String(sha256HMAC.doFinal(postDataString.getBytes()));

             // check the hash generated with signature passed
             return hash.equals(signature);

        } catch (Exception e) {
            e.printStackTrace();
            return false;
        }
    }

}

const Cashfree = require("cashfree-sdk");
//convert post response recived in the notification end point to json
//and pass that to the SDK.
Cashfree.Payouts.VerifySignature(webhookPostDataJson, signature, clientSecret);

from cashfree_sdk import verification

#webhook_data = response.content
webhook_data = '{"cashgramId": "5b8283182e0711eaa4c531df6a4f439b-28", "event": "CASHGRAM_EXPIRED", "eventTime": "2020-01-03 15:01:06", "reason": "OTP_ATTEMPTS_EXCEEDED", "signature": "TBpM+4nr1DsWsov7QiHSTfRJP4Z9BD8XrDgEhBlf9ss="}'
verification.verify_webhook(webhook_data, 'JSON')