Sonar suggestion - use a secure random number generator

Change-Id: I28075845555bcbc384a49e07353b3192c413b8f7
diff --git a/utils/misc/src/main/java/org/onlab/graph/SrlgGraphSearch.java b/utils/misc/src/main/java/org/onlab/graph/SrlgGraphSearch.java
index d455c64..46a7cab 100644
--- a/utils/misc/src/main/java/org/onlab/graph/SrlgGraphSearch.java
+++ b/utils/misc/src/main/java/org/onlab/graph/SrlgGraphSearch.java
@@ -18,13 +18,13 @@
 package org.onlab.graph;
 
 
+import java.security.SecureRandom;
 import java.util.Map;
 import java.util.List;
 import java.util.HashMap;
 import java.util.HashSet;
-import java.util.Set;
 import java.util.Random;
-
+import java.util.Set;
 
 /**
  * SRLG Graph Search finds a pair of paths with disjoint risk groups; i.e
@@ -171,7 +171,7 @@
 
         boolean[] subset;
         boolean[] not;
-        Random r = new Random();
+        Random r = new SecureRandom();
 
         /**
          * Creates a Subset from the given subset array.