diff --git a/src/identity-challenge/challenge-credential.cpp b/src/identity-challenge/challenge-credential.cpp
index b8e493f..3ad014a 100644
--- a/src/identity-challenge/challenge-credential.cpp
+++ b/src/identity-challenge/challenge-credential.cpp
@@ -87,7 +87,7 @@
   size_t signatureLen;
   const auto& elements = params.elements();
   for (size_t i = 0; i < elements.size(); i++) {
-    if (elements[i].type() == tlv_parameter_key) {
+    if (elements[i].type() == tlv::ParameterKey) {
       if (readString(elements[i]) == PARAMETER_KEY_CREDENTIAL_CERT) {
         try {
           credential.wireDecode(elements[i + 1].blockFromValue());
@@ -139,24 +139,24 @@
 ChallengeCredential::genChallengeRequestTLV(Status status, const std::string& challengeStatus,
                                             std::vector<std::tuple<std::string, std::string>>&& params)
 {
-  Block request = makeEmptyBlock(tlv_encrypted_payload);
+  Block request = makeEmptyBlock(tlv::EncryptedPayload);
   if (status == Status::BEFORE_CHALLENGE) {
     if (params.size() != 2) {
       NDN_THROW(std::runtime_error("Wrong parameter provided."));
     }
-    request.push_back(makeStringBlock(tlv_selected_challenge, CHALLENGE_TYPE));
+    request.push_back(makeStringBlock(tlv::SelectedChallenge, CHALLENGE_TYPE));
     for (const auto& item : params) {
       if (std::get<0>(item) == PARAMETER_KEY_CREDENTIAL_CERT) {
-        request.push_back(makeStringBlock(tlv_parameter_key, PARAMETER_KEY_CREDENTIAL_CERT));
-        Block valueBlock = makeEmptyBlock(tlv_parameter_value);
+        request.push_back(makeStringBlock(tlv::ParameterKey, PARAMETER_KEY_CREDENTIAL_CERT));
+        Block valueBlock = makeEmptyBlock(tlv::ParameterValue);
         auto& certTlvStr = std::get<1>(item);
         valueBlock.push_back(Block((uint8_t*)certTlvStr.c_str(), certTlvStr.size()));
         request.push_back(valueBlock);
       }
       else if (std::get<0>(item) == PARAMETER_KEY_PROOF_OF_PRIVATE_KEY) {
-        request.push_back(makeStringBlock(tlv_parameter_key, PARAMETER_KEY_PROOF_OF_PRIVATE_KEY));
+        request.push_back(makeStringBlock(tlv::ParameterKey, PARAMETER_KEY_PROOF_OF_PRIVATE_KEY));
         auto& sigTlvStr = std::get<1>(item);
-        Block valueBlock = makeBinaryBlock(tlv_parameter_value, (uint8_t*)sigTlvStr.c_str(), sigTlvStr.size());
+        Block valueBlock = makeBinaryBlock(tlv::ParameterValue, (uint8_t*)sigTlvStr.c_str(), sigTlvStr.size());
         request.push_back(valueBlock);
       }
       else {
diff --git a/src/identity-challenge/challenge-email.cpp b/src/identity-challenge/challenge-email.cpp
index f08025b..0c65c69 100644
--- a/src/identity-challenge/challenge-email.cpp
+++ b/src/identity-challenge/challenge-email.cpp
@@ -49,7 +49,7 @@
   auto currentTime = time::system_clock::now();
   if (request.m_status == Status::BEFORE_CHALLENGE) {
     // for the first time, init the challenge
-    std::string emailAddress = readString(params.get(tlv_parameter_value));
+    std::string emailAddress = readString(params.get(tlv::ParameterValue));
     if (!isValidEmailAddress(emailAddress)) {
       return returnWithNewChallengeStatus(request, INVALID_EMAIL, JsonSection(), m_maxAttemptTimes - 1, m_secretLifetime);
     }
@@ -70,7 +70,7 @@
         request.m_challengeState->m_challengeStatus == WRONG_CODE) {
       NDN_LOG_TRACE("Challenge Interest arrives. Challenge Status: " << request.m_challengeState->m_challengeStatus);
       // the incoming interest should bring the pin code
-      std::string givenCode = readString(params.get(tlv_parameter_value));
+      std::string givenCode = readString(params.get(tlv::ParameterValue));
       auto secret = request.m_challengeState->m_secrets;
       // check if run out of time
       if (currentTime - request.m_challengeState->m_timestamp >= m_secretLifetime) {
@@ -123,22 +123,22 @@
 Block
 ChallengeEmail::genChallengeRequestTLV(Status status, const std::string& challengeStatus, std::vector<std::tuple<std::string, std::string>>&& params)
 {
-  Block request = makeEmptyBlock(tlv_encrypted_payload);
+  Block request = makeEmptyBlock(tlv::EncryptedPayload);
   if (status == Status::BEFORE_CHALLENGE) {
     if (params.size() != 1 || std::get<0>(params[0]) != PARAMETER_KEY_EMAIL) {
       NDN_THROW(std::runtime_error("Wrong parameter provided."));
     }
-    request.push_back(makeStringBlock(tlv_selected_challenge, CHALLENGE_TYPE));
-    request.push_back(makeStringBlock(tlv_parameter_key, PARAMETER_KEY_EMAIL));
-    request.push_back(makeStringBlock(tlv_parameter_value, std::get<1>(params[0])));
+    request.push_back(makeStringBlock(tlv::SelectedChallenge, CHALLENGE_TYPE));
+    request.push_back(makeStringBlock(tlv::ParameterKey, PARAMETER_KEY_EMAIL));
+    request.push_back(makeStringBlock(tlv::ParameterValue, std::get<1>(params[0])));
   }
   else if (status == Status::CHALLENGE && (challengeStatus == NEED_CODE || challengeStatus == WRONG_CODE)) {
     if (params.size() != 1 || std::get<0>(params[0]) != PARAMETER_KEY_CODE) {
       NDN_THROW(std::runtime_error("Wrong parameter provided."));
     }
-    request.push_back(makeStringBlock(tlv_selected_challenge, CHALLENGE_TYPE));
-    request.push_back(makeStringBlock(tlv_parameter_key, PARAMETER_KEY_CODE));
-    request.push_back(makeStringBlock(tlv_parameter_value, std::get<1>(params[0])));
+    request.push_back(makeStringBlock(tlv::SelectedChallenge, CHALLENGE_TYPE));
+    request.push_back(makeStringBlock(tlv::ParameterKey, PARAMETER_KEY_CODE));
+    request.push_back(makeStringBlock(tlv::ParameterValue, std::get<1>(params[0])));
   }
   else {
     NDN_THROW(std::runtime_error("Unexpected status or challenge status."));
diff --git a/src/identity-challenge/challenge-pin.cpp b/src/identity-challenge/challenge-pin.cpp
index 04bd153..fe17cd1 100644
--- a/src/identity-challenge/challenge-pin.cpp
+++ b/src/identity-challenge/challenge-pin.cpp
@@ -56,7 +56,7 @@
         request.m_challengeState->m_challengeStatus == WRONG_CODE) {
       NDN_LOG_TRACE("Challenge Interest arrives. Challenge Status: " << request.m_challengeState->m_challengeStatus);
       // the incoming interest should bring the pin code
-      std::string givenCode = readString(params.get(tlv_parameter_value));
+      std::string givenCode = readString(params.get(tlv::ParameterValue));
       auto secret = request.m_challengeState->m_secrets;
       if (currentTime - request.m_challengeState->m_timestamp >= m_secretLifetime) {
         return returnWithError(request, ErrorCode::OUT_OF_TIME, "Secret expired.");
@@ -106,17 +106,17 @@
 Block
 ChallengePin::genChallengeRequestTLV(Status status, const std::string& challengeStatus, std::vector<std::tuple<std::string, std::string>>&& params)
 {
-  Block request = makeEmptyBlock(tlv_encrypted_payload);
+  Block request = makeEmptyBlock(tlv::EncryptedPayload);
   if (status == Status::BEFORE_CHALLENGE) {
-    request.push_back(makeStringBlock(tlv_selected_challenge, CHALLENGE_TYPE));
+    request.push_back(makeStringBlock(tlv::SelectedChallenge, CHALLENGE_TYPE));
   }
   else if (status == Status::CHALLENGE && (challengeStatus == NEED_CODE || challengeStatus == WRONG_CODE)) {
     if (params.size() != 1 || std::get<0>(params[0]) != PARAMETER_KEY_CODE) {
       NDN_THROW(std::runtime_error("Wrong parameter provided."));
     }
-    request.push_back(makeStringBlock(tlv_selected_challenge, CHALLENGE_TYPE));
-    request.push_back(makeStringBlock(tlv_parameter_key, PARAMETER_KEY_CODE));
-    request.push_back(makeStringBlock(tlv_parameter_value, std::get<1>(params[0])));
+    request.push_back(makeStringBlock(tlv::SelectedChallenge, CHALLENGE_TYPE));
+    request.push_back(makeStringBlock(tlv::ParameterKey, PARAMETER_KEY_CODE));
+    request.push_back(makeStringBlock(tlv::ParameterValue, std::get<1>(params[0])));
   }
   else {
     NDN_THROW(std::runtime_error("Unexpected status or challenge status."));