diff --git a/src/detail/ca-request-state.cpp b/src/detail/ca-request-state.cpp
index 0de0820..923f9be 100644
--- a/src/detail/ca-request-state.cpp
+++ b/src/detail/ca-request-state.cpp
@@ -24,7 +24,8 @@
 namespace ndn {
 namespace ndncert {
 
-std::string statusToString(Status status) {
+std::string statusToString(Status status)
+{
   switch (status)
   {
   case Status::BEFORE_CHALLENGE:
@@ -46,6 +47,15 @@
   }
 }
 
+Status
+statusFromBlock(const Block& block)
+{
+  auto status_int = readNonNegativeInteger(block);
+  if (status_int > 6)
+      NDN_THROW(std::runtime_error("Unrecognized Status"));
+  return static_cast<Status>(status_int);
+}
+
 namespace ca {
 
 ChallengeState::ChallengeState(const std::string& challengeStatus,
diff --git a/src/detail/ca-request-state.hpp b/src/detail/ca-request-state.hpp
index 7fa9f23..27d19fa 100644
--- a/src/detail/ca-request-state.hpp
+++ b/src/detail/ca-request-state.hpp
@@ -45,6 +45,12 @@
 std::string
 statusToString(Status status);
 
+/**
+ * @brief Convert request status to string.
+ */
+Status
+statusFromBlock(const Block& block);
+
 namespace ca {
 
 /**
diff --git a/src/detail/challenge-encoder.cpp b/src/detail/challenge-encoder.cpp
index 22dc6c7..c9fa34b 100644
--- a/src/detail/challenge-encoder.cpp
+++ b/src/detail/challenge-encoder.cpp
@@ -24,10 +24,10 @@
 namespace ndncert {
 
 Block
-ChallengeEncoder::encodeDataContent(ca::RequestState& request, optional<Name> issuedCertName)
+ChallengeEncoder::encodeDataContent(ca::RequestState& request, const Name& issuedCertName)
 {
   Block response = makeEmptyBlock(tlv::EncryptedPayload);
-  response.push_back(makeNonNegativeIntegerBlock(tlv::Status, static_cast<size_t>(request.m_status)));
+  response.push_back(makeNonNegativeIntegerBlock(tlv::Status, static_cast<uint64_t>(request.m_status)));
   if (request.m_challengeState) {
     response.push_back(makeStringBlock(tlv::ChallengeStatus, request.m_challengeState->m_challengeStatus));
     response.push_back(
@@ -35,8 +35,8 @@
     response.push_back(
         makeNonNegativeIntegerBlock(tlv::RemainingTime, request.m_challengeState->m_remainingTime.count()));
   }
-  if (issuedCertName.has_value()) {
-    response.push_back(makeNestedBlock(tlv::IssuedCertName, *issuedCertName));
+  if (!issuedCertName.empty()) {
+    response.push_back(makeNestedBlock(tlv::IssuedCertName, issuedCertName));
   }
   response.encode();
   return encodeBlockWithAesGcm128(ndn::tlv::Content, request.m_encryptionKey.data(),
@@ -45,13 +45,13 @@
 }
 
 void
-ChallengeEncoder::decodeDataContent(const Block& contentBlock, requester::RequestContext& state)
+ChallengeEncoder::decodeDataContent(const Block& contentBlock, requester::RequestState& state)
 {
   auto result = decodeBlockWithAesGcm128(contentBlock, state.m_aesKey.data(),
                                          state.m_requestId.data(), state.m_requestId.size());
   auto data = makeBinaryBlock(tlv::EncryptedPayload, result.data(), result.size());
   data.parse();
-  state.m_status = static_cast<Status>(readNonNegativeInteger(data.get(tlv::Status)));
+  state.m_status = statusFromBlock(data.get(tlv::Status));
   if (data.find(tlv::ChallengeStatus) != data.elements_end()) {
     state.m_challengeStatus = readString(data.get(tlv::ChallengeStatus));
   }
diff --git a/src/detail/challenge-encoder.hpp b/src/detail/challenge-encoder.hpp
index 3eaf4c4..4aa3b5a 100644
--- a/src/detail/challenge-encoder.hpp
+++ b/src/detail/challenge-encoder.hpp
@@ -22,7 +22,7 @@
 #define NDNCERT_DETAIL_CHALLENGE_ENCODER_HPP
 
 #include "detail/ca-request-state.hpp"
-#include "requester-state.hpp"
+#include "requester-request-state.hpp"
 
 namespace ndn {
 namespace ndncert {
@@ -31,10 +31,10 @@
 {
 public:
   static Block
-  encodeDataContent(ca::RequestState& request, optional<Name> issuedCertName = nullopt);
+  encodeDataContent(ca::RequestState& request, const Name& issuedCertName = Name());
 
   static void
-  decodeDataContent(const Block& data, requester::RequestContext& state);
+  decodeDataContent(const Block& contentBlock, requester::RequestState& state);
 };
 
 } // namespace ndncert
diff --git a/src/detail/new-renew-revoke-encoder.cpp b/src/detail/new-renew-revoke-encoder.cpp
index 577d1de..fd4f48c 100644
--- a/src/detail/new-renew-revoke-encoder.cpp
+++ b/src/detail/new-renew-revoke-encoder.cpp
@@ -101,7 +101,7 @@
                                          std::array<uint8_t, 32>& salt, RequestId& requestId, Status& status)
 {
   content.parse();
-  status = static_cast<Status>(readNonNegativeInteger(content.get(tlv::Status)));
+  status = statusFromBlock(content.get(tlv::Status));
 
   const auto& ecdhBlock = content.get(tlv::EcdhPub);
   ecdhKey.resize(ecdhBlock.value_size());