Use PendingInterestHandle and ScopedRegisteredPrefixHandle

Refs: #3919, #4316
Change-Id: I1cc5dcda07ae50e5c1afa067d1a00227f71c2233
diff --git a/src/encryptor.hpp b/src/encryptor.hpp
index 21a9297..9656674 100644
--- a/src/encryptor.hpp
+++ b/src/encryptor.hpp
@@ -139,8 +139,8 @@
   ErrorCallback m_onFailure;
 
   InMemoryStoragePersistent m_ims; // for encrypted CKs
-  const RegisteredPrefixId* m_ckRegId = nullptr;
-  const PendingInterestId* m_kekPendingInterest = nullptr;
+  ScopedRegisteredPrefixHandle m_ckReg;
+  PendingInterestHandle m_kekPendingInterest;
 
   KeyChain& m_keyChain;
   Face& m_face;