diff --git a/src/daemon/name-server.cpp b/src/daemon/name-server.cpp
index 70288ec..11ad3a8 100644
--- a/src/daemon/name-server.cpp
+++ b/src/daemon/name-server.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
-/**
- * Copyright (c) 2014-2016, Regents of the University of California.
+/*
+ * Copyright (c) 2014-2017, Regents of the University of California.
  *
  * This file is part of NDNS (Named Data Networking Domain Name Service).
  * See AUTHORS.md for complete list of NDNS authors and contributors.
@@ -20,6 +20,7 @@
 #include "name-server.hpp"
 #include "logger.hpp"
 #include <ndn-cxx/encoding/encoding-buffer.hpp>
+#include <ndn-cxx/security/signing-helpers.hpp>
 
 namespace ndn {
 namespace ndns {
@@ -28,44 +29,32 @@
 const time::milliseconds NAME_SERVER_DEFAULT_CONTENT_FRESHNESS(4000);
 
 NameServer::NameServer(const Name& zoneName, const Name& certName, Face& face, DbMgr& dbMgr,
-                       KeyChain& keyChain, Validator& validator)
+                       KeyChain& keyChain, security::v2::Validator& validator)
   : m_zone(zoneName)
   , m_dbMgr(dbMgr)
   , m_ndnsPrefix(zoneName)
-  , m_keyPrefix(zoneName)
   , m_certName(certName)
   , m_contentFreshness(NAME_SERVER_DEFAULT_CONTENT_FRESHNESS)
   , m_face(face)
   , m_keyChain(keyChain)
   , m_validator(validator)
 {
-  if (!m_keyChain.doesCertificateExist(m_certName)) {
-    NDNS_LOG_FATAL("Certificate: " << m_certName << " does not exist");
-    throw Error("certificate does not exist in the KeyChain: " + m_certName.toUri());
-  }
-
   m_dbMgr.find(m_zone);
 
   if (m_zone.getId() == 0) {
     NDNS_LOG_FATAL("m_zone does not exist: " << zoneName);
-    throw Error("Zone " + zoneName.toUri() + " does not exist in the database");
+    BOOST_THROW_EXCEPTION(Error("Zone " + zoneName.toUri() + " does not exist in the database"));
   }
 
   m_ndnsPrefix.append(ndns::label::NDNS_ITERATIVE_QUERY);
-  m_keyPrefix.append(ndns::label::NDNS_CERT_QUERY);
 
   m_face.setInterestFilter(m_ndnsPrefix,
                            bind(&NameServer::onInterest, this, _1, _2),
                            bind(&NameServer::onRegisterFailed, this, _1, _2)
                            );
 
-  m_face.setInterestFilter(m_keyPrefix,
-                           bind(&NameServer::onInterest, this, _1, _2),
-                           bind(&NameServer::onRegisterFailed, this, _1, _2)
-                           );
-
   NDNS_LOG_INFO("Zone: " << m_zone.getName() << " binds "
-                << "Prefix: " << m_ndnsPrefix << " and " << m_keyPrefix
+                << "Prefix: " << m_ndnsPrefix
                 << " with Certificate: " << m_certName
                 );
 }
@@ -109,7 +98,7 @@
     answer->setFreshnessPeriod(this->getContentFreshness());
     answer->setContentType(NDNS_NACK);
 
-    m_keyChain.sign(*answer, m_certName);
+    m_keyChain.sign(*answer, signingByCertificate(m_certName));
     NDNS_LOG_TRACE("answer query with NDNS-NACK: " << answer->getName());
     m_face.put(*answer);
   }
@@ -127,13 +116,13 @@
       const Block& block = it->blockFromValue();
       data = make_shared<Data>(block);
     }
-    catch (std::exception& e) {
+    catch (const std::exception& e) {
       NDNS_LOG_WARN("exception when getting update info: " << e.what());
       return;
     }
     m_validator.validate(*data,
                          bind(&NameServer::doUpdate, this, interest.shared_from_this(), data),
-                         [this] (const shared_ptr<const Data>& data, const std::string& msg) {
+                         [this] (const Data& data, const security::v2::ValidationError& msg) {
                            NDNS_LOG_WARN("Ignoring update that did not pass the verification. "
                                          << "Check the root certificate")
                          });
@@ -144,8 +133,8 @@
 NameServer::onRegisterFailed(const ndn::Name& prefix, const std::string& reason)
 {
   NDNS_LOG_FATAL("fail to register prefix=" << prefix << ". Due to: " << reason);
-  throw Error("zone " + m_zone.getName().toUri() + " register prefix: " +
-              prefix.toUri() + " fails. due to: " + reason);
+  BOOST_THROW_EXCEPTION(Error("zone " + m_zone.getName().toUri() + " register prefix: " +
+                              prefix.toUri() + " fails. due to: " + reason));
 }
 
 void
@@ -157,7 +146,7 @@
     if (!label::matchName(*data, m_zone.getName(), re))
       return;
   }
-  catch (std::exception& e) {
+  catch (const std::exception& e) {
     NDNS_LOG_INFO("Error while name/certificate matching: " << e.what());
   }
 
@@ -204,7 +193,7 @@
       NDNS_LOG_TRACE("insert new record and answer update with UPDATE_OK");
     }
   }
-  catch (std::exception& e) {
+  catch (const std::exception& e) {
     blk.push_back(makeNonNegativeIntegerBlock(ndn::ndns::tlv::UpdateReturnCode, UPDATE_FAILURE));
     blk.encode(); // must
     answer->setContent(blk);
@@ -212,7 +201,7 @@
                   << ". Update may need sudo privilege to write DbFile");
     NDNS_LOG_TRACE("exception happens and answer update with UPDATE_FAILURE");
   }
-  m_keyChain.sign(*answer, m_certName);
+  m_keyChain.sign(*answer, signingByCertificate(m_certName));
   m_face.put(*answer);
 }