diff --git a/tests/unit/security/pib/impl/key-impl.t.cpp b/tests/unit/security/pib/impl/key-impl.t.cpp
new file mode 100644
index 0000000..e6860be
--- /dev/null
+++ b/tests/unit/security/pib/impl/key-impl.t.cpp
@@ -0,0 +1,200 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/*
+ * Copyright (c) 2013-2018 Regents of the University of California.
+ *
+ * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
+ *
+ * ndn-cxx library is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU Lesser General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later version.
+ *
+ * ndn-cxx library is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+ * PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more details.
+ *
+ * You should have received copies of the GNU General Public License and GNU Lesser
+ * General Public License along with ndn-cxx, e.g., in COPYING.md file.  If not, see
+ * <http://www.gnu.org/licenses/>.
+ *
+ * See AUTHORS.md for complete list of ndn-cxx authors and contributors.
+ */
+
+#include "ndn-cxx/security/pib/impl/key-impl.hpp"
+#include "ndn-cxx/security/pib/pib.hpp"
+#include "ndn-cxx/security/pib/pib-memory.hpp"
+
+#include "tests/boost-test.hpp"
+#include "tests/identity-management-fixture.hpp"
+#include "tests/unit/security/pib/pib-data-fixture.hpp"
+
+namespace ndn {
+namespace security {
+namespace pib {
+namespace detail {
+namespace tests {
+
+BOOST_AUTO_TEST_SUITE(Security)
+BOOST_AUTO_TEST_SUITE(Pib)
+BOOST_AUTO_TEST_SUITE(Detail)
+BOOST_FIXTURE_TEST_SUITE(TestKeyImpl, security::tests::PibDataFixture)
+
+using security::Pib;
+
+BOOST_AUTO_TEST_CASE(Basic)
+{
+  auto pibImpl = make_shared<pib::PibMemory>();
+  KeyImpl key11(id1Key1Name, id1Key1.data(), id1Key1.size(), pibImpl);
+
+  BOOST_CHECK_EQUAL(key11.getName(), id1Key1Name);
+  BOOST_CHECK_EQUAL(key11.getIdentity(), id1);
+  BOOST_CHECK_EQUAL(key11.getKeyType(), KeyType::EC);
+  BOOST_CHECK(key11.getPublicKey() == id1Key1);
+
+  KeyImpl key11Bak(id1Key1Name, pibImpl);
+  BOOST_CHECK_EQUAL(key11Bak.getName(), id1Key1Name);
+  BOOST_CHECK_EQUAL(key11Bak.getIdentity(), id1);
+  BOOST_CHECK_EQUAL(key11Bak.getKeyType(), KeyType::EC);
+  BOOST_CHECK(key11Bak.getPublicKey() == id1Key1);
+}
+
+BOOST_AUTO_TEST_CASE(CertificateOperation)
+{
+  auto pibImpl = make_shared<pib::PibMemory>();
+  KeyImpl key11(id1Key1Name, id1Key1.data(), id1Key1.size(), pibImpl);
+  BOOST_CHECK_NO_THROW(KeyImpl(id1Key1Name, pibImpl));
+
+  // key does not have any certificate
+  BOOST_CHECK_EQUAL(key11.getCertificates().size(), 0);
+
+  // get non-existing certificate, throw Pib::Error
+  BOOST_CHECK_THROW(key11.getCertificate(id1Key1Cert1.getName()), Pib::Error);
+  // get default certificate, throw Pib::Error
+  BOOST_CHECK_THROW(key11.getDefaultCertificate(), Pib::Error);
+  // set non-existing certificate as default certificate, throw Pib::Error
+  BOOST_REQUIRE_THROW(key11.setDefaultCertificate(id1Key1Cert1.getName()), Pib::Error);
+
+  // add certificate
+  key11.addCertificate(id1Key1Cert1);
+  BOOST_CHECK_NO_THROW(key11.getCertificate(id1Key1Cert1.getName()));
+
+  // new certificate becomes default certificate when there was no default certificate
+  BOOST_REQUIRE_NO_THROW(key11.getDefaultCertificate());
+  const auto& defaultCert0 = key11.getDefaultCertificate();
+  BOOST_CHECK_EQUAL(defaultCert0.getName(), id1Key1Cert1.getName());
+  BOOST_CHECK_EQUAL(defaultCert0, id1Key1Cert1);
+
+  // remove certificate
+  key11.removeCertificate(id1Key1Cert1.getName());
+  BOOST_CHECK_THROW(key11.getCertificate(id1Key1Cert1.getName()), Pib::Error);
+  BOOST_CHECK_THROW(key11.getDefaultCertificate(), Pib::Error);
+
+  // set default certificate directly
+  BOOST_REQUIRE_NO_THROW(key11.setDefaultCertificate(id1Key1Cert1));
+  BOOST_REQUIRE_NO_THROW(key11.getDefaultCertificate());
+  BOOST_CHECK_NO_THROW(key11.getCertificate(id1Key1Cert1.getName()));
+
+  // check default cert
+  const auto& defaultCert1 = key11.getDefaultCertificate();
+  BOOST_CHECK_EQUAL(defaultCert1.getName(), id1Key1Cert1.getName());
+  BOOST_CHECK_EQUAL(defaultCert1, id1Key1Cert1);
+
+  // add another certificate
+  key11.addCertificate(id1Key1Cert2);
+  BOOST_CHECK_EQUAL(key11.getCertificates().size(), 2);
+
+  // set default certificate through name
+  BOOST_REQUIRE_NO_THROW(key11.setDefaultCertificate(id1Key1Cert2.getName()));
+  BOOST_REQUIRE_NO_THROW(key11.getDefaultCertificate());
+  const auto& defaultCert2 = key11.getDefaultCertificate();
+  BOOST_CHECK_EQUAL(defaultCert2.getName(), id1Key1Cert2.getName());
+  BOOST_CHECK_EQUAL(defaultCert2, id1Key1Cert2);
+
+  // remove certificate
+  key11.removeCertificate(id1Key1Cert1.getName());
+  BOOST_CHECK_THROW(key11.getCertificate(id1Key1Cert1.getName()), Pib::Error);
+  BOOST_CHECK_EQUAL(key11.getCertificates().size(), 1);
+
+  // set default certificate directly again, change the default setting
+  BOOST_REQUIRE_NO_THROW(key11.setDefaultCertificate(id1Key1Cert1));
+  const auto& defaultCert3 = key11.getDefaultCertificate();
+  BOOST_CHECK_EQUAL(defaultCert3.getName(), id1Key1Cert1.getName());
+  BOOST_CHECK_EQUAL(defaultCert3, id1Key1Cert1);
+  BOOST_CHECK_EQUAL(key11.getCertificates().size(), 2);
+
+  // remove all certificates
+  key11.removeCertificate(id1Key1Cert1.getName());
+  BOOST_CHECK_THROW(key11.getCertificate(id1Key1Cert1.getName()), Pib::Error);
+  BOOST_CHECK_EQUAL(key11.getCertificates().size(), 1);
+  key11.removeCertificate(id1Key1Cert2.getName());
+  BOOST_CHECK_THROW(key11.getCertificate(id1Key1Cert2.getName()), Pib::Error);
+  BOOST_CHECK_THROW(key11.getDefaultCertificate(), Pib::Error);
+  BOOST_CHECK_EQUAL(key11.getCertificates().size(), 0);
+}
+
+class OverwriteFixture : public ndn::security::tests::PibDataFixture,
+                         public ndn::tests::IdentityManagementFixture
+{
+};
+
+BOOST_FIXTURE_TEST_CASE(Overwrite, OverwriteFixture)
+{
+  auto pibImpl = make_shared<pib::PibMemory>();
+
+  BOOST_CHECK_THROW(KeyImpl(id1Key1Name, pibImpl), Pib::Error);
+  KeyImpl(id1Key1Name, id1Key1.data(), id1Key1.size(), pibImpl);
+  KeyImpl key1(id1Key1Name, pibImpl);
+
+  KeyImpl(id1Key1Name, id1Key2.data(), id1Key2.size(), pibImpl); // overwriting of the key should work
+  KeyImpl key2(id1Key1Name, pibImpl);
+
+  BOOST_CHECK(key1.getPublicKey() != key2.getPublicKey()); // key1 cached the original public key
+  BOOST_CHECK(key2.getPublicKey() == id1Key2);
+
+  key1.addCertificate(id1Key1Cert1);
+  BOOST_CHECK_EQUAL(key1.getCertificate(id1Key1Cert1.getName()), id1Key1Cert1);
+
+  auto otherCert = id1Key1Cert1;
+  SignatureInfo info;
+  info.setValidityPeriod(ValidityPeriod(time::system_clock::now(),
+                                        time::system_clock::now() + 1_s));
+  m_keyChain.sign(otherCert, SigningInfo().setSignatureInfo(info));
+
+  BOOST_CHECK_EQUAL(otherCert.getName(), id1Key1Cert1.getName());
+  BOOST_CHECK(otherCert.getContent() == id1Key1Cert1.getContent());
+  BOOST_CHECK_NE(otherCert, id1Key1Cert1);
+
+  key1.addCertificate(otherCert);
+
+  BOOST_CHECK_EQUAL(key1.getCertificate(id1Key1Cert1.getName()), otherCert);
+}
+
+BOOST_AUTO_TEST_CASE(Errors)
+{
+  auto pibImpl = make_shared<pib::PibMemory>();
+
+  BOOST_CHECK_THROW(KeyImpl(id1Key1Name, pibImpl), Pib::Error);
+  KeyImpl key11(id1Key1Name, id1Key1.data(), id1Key1.size(), pibImpl);
+
+  BOOST_CHECK_THROW(KeyImpl(Name("/wrong"), pibImpl), std::invalid_argument);
+  BOOST_CHECK_THROW(KeyImpl(Name("/wrong"), id1Key1.data(), id1Key1.size(), pibImpl), std::invalid_argument);
+  Buffer wrongKey;
+  BOOST_CHECK_THROW(KeyImpl(id1Key2Name, wrongKey.data(), wrongKey.size(), pibImpl), std::invalid_argument);
+
+  key11.addCertificate(id1Key1Cert1);
+  BOOST_CHECK_THROW(key11.addCertificate(id1Key2Cert1), std::invalid_argument);
+  BOOST_CHECK_THROW(key11.removeCertificate(id1Key2Cert1.getName()), std::invalid_argument);
+  BOOST_CHECK_THROW(key11.getCertificate(id1Key2Cert1.getName()), std::invalid_argument);
+  BOOST_CHECK_THROW(key11.setDefaultCertificate(id1Key2Cert1), std::invalid_argument);
+  BOOST_CHECK_THROW(key11.setDefaultCertificate(id1Key2Cert1.getName()), std::invalid_argument);
+}
+
+BOOST_AUTO_TEST_SUITE_END() // TestKeyImpl
+BOOST_AUTO_TEST_SUITE_END() // Detail
+BOOST_AUTO_TEST_SUITE_END() // Pib
+BOOST_AUTO_TEST_SUITE_END() // Security
+
+} // namespace tests
+} // namespace detail
+} // namespace pib
+} // namespace security
+} // namespace ndn