如何簽署URL Google路線？

我有一個函數可以檢索Google Directions，但我有一個關於在哪裏可以找到Google Crypto Key來簽署我的URL的問題。儀表板上的這個在哪裏？如何簽署URL Google路線？

 public static void getDirections(Context context, String origin, String destination, 
             final DirectionsListener listener) 
       throws ExecutionException, InterruptedException { 
      if (FrameworkUtils.isStringEmpty(origin) || FrameworkUtils.isStringEmpty(destination)) { 
       return; 
      } 
      try { 
       String url = String.format(GOOGLE_API_DIRECTIONS_URL, origin, destination, 
         ConfigurationManager.GOOGLE_CLIENT_KEY, KEY_TRAVEL_MODE_DRIVING); 
       String signedUrl = UrlSigner.signURL(url); 
       JsonRequest request = new JsonRequest(Method.GET, signedUrl, null, new JsonResponseListener() { 
        @Override 
        public void onResponse(JSONObject response, int resultCode) { 
         try { 
          JSONArray routesObject = response.getJSONArray(KEY_ROUTES); 
          JSONObject currentRoute = routesObject.getJSONObject(0); 
          JSONObject overViewPolyline = currentRoute.getJSONObject(KEY_OVERVIEW_POLYLINE); 
          String encodedPoints = overViewPolyline.getString(KEY_POINTS); 
          listener.onSuccess(decode(encodedPoints)); 
         } catch (JSONException e) { 
          e.printStackTrace(); 
         } 
        } 

        @Override 
        public void onResponse(JSONObject jsonObject) { 
         // do nothing 
        } 
       }, new ErrorListener() { 
        @Override 
        public void onErrorResponse(VolleyError volleyError) { 
         // do nothing 
        } 

        @Override 
        public void onErrorResponse(VolleyError error, int resultCode) { 
         // do nothing 
        } 
       }, 45); 
    VolleyClient.getInstance(context.getApplicationContext()).addRequest(request); 
      } catch (IOException | InvalidKeyException | NoSuchAlgorithmException | URISyntaxException e) { 
       e.printStackTrace(); 
      } 
     }

這裏是我的signURL功能

public static String signURL(String inputUrl) throws IOException, InvalidKeyException, NoSuchAlgorithmException, URISyntaxException { 
    URL url = new URL(inputUrl); 
    String googleCryptoKey = ConfigurationManager.GOOGLE_CRYPTO_KEY; 
    UrlSigner signer = new UrlSigner(googleCryptoKey); 
    String request = signer.signRequest(url.getPath(), url.getQuery()); 
    return url.getProtocol() + "://" + url.getHost() + request; 
}

我創建從例子的代碼，但我摸不清的谷歌加密密鑰應該是什麼？

儀表板具有