diff --git a/include/ndn-cpp/security/identity/identity-manager.hpp b/include/ndn-cpp/security/identity/identity-manager.hpp
index d5f49f4..4273f6b 100644
--- a/include/ndn-cpp/security/identity/identity-manager.hpp
+++ b/include/ndn-cpp/security/identity/identity-manager.hpp
@@ -9,18 +9,22 @@
 #ifndef NDN_IDENTITY_MANAGER_HPP
 #define NDN_IDENTITY_MANAGER_HPP
 
-#include "../certificate/identity-certificate.hpp"
 #include "identity-storage.hpp"
-#include "../certificate/public-key.hpp"
 #include "private-key-storage.hpp"
 
+#include "../../data.hpp"
+
 namespace ndn {
 
+class IdentityCertificate;
+
 /**
  * An IdentityManager is the interface of operations related to identity, keys, and certificates.
  */
 class IdentityManager {
 public:
+  struct Error : public std::runtime_error { Error(const std::string &what) : std::runtime_error(what) {} };
+
   IdentityManager(const ptr_lib::shared_ptr<IdentityStorage>& identityStorage, const ptr_lib::shared_ptr<PrivateKeyStorage>& privateKeyStorage)
   : identityStorage_(identityStorage), privateKeyStorage_(privateKeyStorage)
   {
@@ -91,11 +95,11 @@
    * @param keyName The name of the key.
    * @return The public key.
    */
-  ptr_lib::shared_ptr<PublicKey>
-  getPublicKey(const Name& keyName)
-  {
-    return PublicKey::fromDer(identityStorage_->getKey(keyName));
-  }
+  // ptr_lib::shared_ptr<PublicKey>
+  // getPublicKey(const Name& keyName)
+  // {
+  //   return PublicKey::fromDer(identityStorage_->getKey(keyName));
+  // }
 
   /**
    * Create an identity certificate for a public key managed by this IdentityManager.
@@ -160,22 +164,22 @@
    * @param certificateName The name of the requested certificate.
    * @return the requested certificate which is valid.
    */
-  ptr_lib::shared_ptr<IdentityCertificate>
-  getCertificate(const Name& certificateName)
-  {
-    return ptr_lib::make_shared<IdentityCertificate>(*identityStorage_->getCertificate(certificateName, false));
-  }
+  // ptr_lib::shared_ptr<IdentityCertificate>
+  // getCertificate(const Name& certificateName)
+  // {
+  //   return ptr_lib::make_shared<IdentityCertificate>(*identityStorage_->getCertificate(certificateName, false));
+  // }
     
   /**
    * Get a certificate even if the certificate is not valid anymore.
    * @param certificateName The name of the requested certificate.
    * @return the requested certificate.
    */
-  ptr_lib::shared_ptr<IdentityCertificate>
-  getAnyCertificate(const Name& certificateName)
-  {
-    return ptr_lib::make_shared<IdentityCertificate>(*identityStorage_->getCertificate(certificateName, true));
-  }
+  // ptr_lib::shared_ptr<IdentityCertificate>
+  // getAnyCertificate(const Name& certificateName)
+  // {
+  //   return ptr_lib::make_shared<IdentityCertificate>(*identityStorage_->getCertificate(certificateName, true));
+  // }
     
   /**
    * Get the default certificate name for the specified identity, which will be used when signing is performed based on identity.
@@ -206,22 +210,10 @@
    * @param certificateName The signing certificate name.
    * @return The generated signature.
    */
-  ptr_lib::shared_ptr<Signature>
+  Signature
   signByCertificate(const uint8_t* buffer, size_t bufferLength, const Name& certificateName);
 
   /**
-   * Sign the byte array data based on the certificate name.
-   * @param buffer The byte array to be signed.
-   * @param certificateName The signing certificate name.
-   * @return The generated signature.
-   */
-  ptr_lib::shared_ptr<Signature>
-  signByCertificate(const std::vector<uint8_t>& buffer, const Name& certificateName) 
-  {
-    return signByCertificate(&buffer[0], buffer.size(), certificateName);
-  }
-
-  /**
    * Sign data packet based on the certificate name.
    * Note: the caller must make sure the timestamp in data is correct, for example with 
    * data.getMetaInfo().setTimestampMilliseconds(time(NULL) * 1000.0).
@@ -230,7 +222,7 @@
    * @param wireFormat The WireFormat for calling encodeData, or WireFormat::getDefaultWireFormat() if omitted.
    */
   void 
-  signByCertificate(Data& data, const Name& certificateName, WireFormat& wireFormat = *WireFormat::getDefaultWireFormat());
+  signByCertificate(Data& data, const Name& certificateName);
 
   /**
    * Generate a self-signed certificate for a public key.
diff --git a/include/ndn-cpp/security/identity/identity-storage.hpp b/include/ndn-cpp/security/identity/identity-storage.hpp
index 3c298c8..442e522 100644
--- a/include/ndn-cpp/security/identity/identity-storage.hpp
+++ b/include/ndn-cpp/security/identity/identity-storage.hpp
@@ -25,6 +25,8 @@
  */
 class IdentityStorage {
 public:
+  struct Error : public std::runtime_error { Error(const std::string &what) : std::runtime_error(what) {} };
+
   /**
    * The virtual Destructor.
    */
@@ -77,14 +79,14 @@
    * @param publicKeyDer A blob of the public key DER to be added.
    */
   virtual void 
-  addKey(const Name& keyName, KeyType keyType, const Blob& publicKeyDer) = 0;
+  addKey(const Name& keyName, KeyType keyType, const Buffer& publicKeyDer) = 0;
 
   /**
    * Get the public key DER blob from the identity storage.
    * @param keyName The name of the requested public key.
    * @return The DER Blob.  If not found, return a Blob with a null pointer.
    */
-  virtual Blob
+  virtual Buffer
   getKey(const Name& keyName) = 0;
 
   /**
diff --git a/include/ndn-cpp/security/identity/private-key-storage.hpp b/include/ndn-cpp/security/identity/private-key-storage.hpp
index 90556bd..c789d89 100644
--- a/include/ndn-cpp/security/identity/private-key-storage.hpp
+++ b/include/ndn-cpp/security/identity/private-key-storage.hpp
@@ -10,13 +10,13 @@
 #define NDN_PRIVATE_KEY_STORAGE_HPP
 
 #include <string>
-#include "../../util/blob.hpp"
-#include "../certificate/public-key.hpp"
 #include "../security-common.hpp"
 #include "../../name.hpp"
 
 namespace ndn {
 
+class PublicKey;
+
 class PrivateKeyStorage {
 public:
   /**
@@ -50,15 +50,9 @@
    * @param digestAlgorithm the digest algorithm.
    * @return The signature, or a null pointer if signing fails.
    */  
-  virtual Blob 
+  virtual ConstBufferPtr
   sign(const uint8_t *data, size_t dataLength, const Name& keyName, DigestAlgorithm digestAlgorithm = DIGEST_ALGORITHM_SHA256) = 0;
     
-  Blob 
-  sign(const Blob& data, const Name& keyName, DigestAlgorithm digestAlgorithm = DIGEST_ALGORITHM_SHA256)
-  {
-    return sign(data.buf(), data.size(), keyName, digestAlgorithm);
-  }
-  
   /**
    * Decrypt data.
    * @param keyName The name of the decrypting key.
@@ -67,15 +61,9 @@
    * @param isSymmetric If true symmetric encryption is used, otherwise asymmetric encryption is used.
    * @return The decrypted data.
    */
-  virtual Blob 
+  virtual ConstBufferPtr 
   decrypt(const Name& keyName, const uint8_t* data, size_t dataLength, bool isSymmetric = false) = 0;
 
-  Blob 
-  decrypt(const Name& keyName, const Blob& data, bool isSymmetric = false)
-  {
-    return decrypt(keyName, data.buf(), data.size(), isSymmetric);
-  }
-
   /**
    * Encrypt data.
    * @param keyName The name of the encrypting key.
@@ -84,15 +72,9 @@
    * @param isSymmetric If true symmetric encryption is used, otherwise asymmetric encryption is used.
    * @return The encrypted data.
    */
-  virtual Blob
+  virtual ConstBufferPtr
   encrypt(const Name& keyName, const uint8_t* data, size_t dataLength, bool isSymmetric = false) = 0;
 
-  Blob
-  encrypt(const Name& keyName, const Blob& data, bool isSymmetric = false)
-  {
-    return encrypt(keyName, data.buf(), data.size(), isSymmetric);
-  }
-
   /**
    * @brief Generate a symmetric key.
    * @param keyName The name of the key.