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."));