diff --git a/ServerDocument.md b/ServerDocument.md
index 95a6af6..47ffe6d 100644
--- a/ServerDocument.md
+++ b/ServerDocument.md
@@ -49,7 +49,7 @@
 	 * @param request
 	 * @return
 	 */
-	public String sig(HttpServletRequest request){
+	public String sig(HttpServletRequest request, String key){
 		
 		Enumeration names = request.getParameterNames();
 		SortedSet<String> allParams = Sets.newTreeSet();
@@ -66,7 +66,9 @@
 				e.printStackTrace();
 			}
 		}
-		String computedToken = DigestUtils.md5DigestAsHex(Joiner.on("&").join(allParams).getBytes());
+		
+		String params = Joiner.on("&").join(allParams)+key;
+		String computedToken = DigestUtils.md5DigestAsHex(params.getBytes());
 		return computedToken;
 	}
 ```