i m getting this response in a result of GET request to server
{\"LL\": { \"control\": \"dev/sys/getkey\", \"value\": \"4545453030304138303046392035343733373
you can parse current json String to get value
from it as :
// Convert String to json object
JSONObject json = new JSONObject(responseText);
// get LL json object
JSONObject json_LL = json.getJSONObject("LL");
// get value from LL Json Object
String str_value=json_LL.getString("value"); //<< get value here