update request id generation

Change-Id: I72d864385093a5f1d849d6e9cfe4e6d5ee2882ac
diff --git a/src/ca-module.hpp b/src/ca-module.hpp
index 8172688..ac2a741 100644
--- a/src/ca-module.hpp
+++ b/src/ca-module.hpp
@@ -109,7 +109,7 @@
   CaConfig m_config;
   unique_ptr<CaStorage> m_storage;
   security::v2::KeyChain& m_keyChain;
-  uint8_t m_requestIdGenKey[16];
+  uint8_t m_requestIdGenKey[32];
 
   std::list<RegisteredPrefixHandle> m_registeredPrefixHandles;
   std::list<InterestFilterHandle> m_interestFilterHandles;