diff --git a/src/ndncert-common.hpp b/src/ndncert-common.hpp
index 4109d58..cbbba39 100644
--- a/src/ndncert-common.hpp
+++ b/src/ndncert-common.hpp
@@ -35,44 +35,42 @@
 #define PROTECTED_WITH_TESTS_ELSE_PRIVATE private
 #endif
 
-#include <cstddef>
-#include <cstdint>
-
-#include <ndn-cxx/interest.hpp>
-#include <ndn-cxx/data.hpp>
-#include <ndn-cxx/name.hpp>
-#include <ndn-cxx/face.hpp>
-#include <ndn-cxx/link.hpp>
-#include <ndn-cxx/encoding/block.hpp>
-#include <ndn-cxx/lp/nack.hpp>
-#include <ndn-cxx/security/key-chain.hpp>
-#include <ndn-cxx/security/v2/certificate.hpp>
-
 #include <boost/algorithm/string.hpp>
 #include <boost/assert.hpp>
 #include <boost/noncopyable.hpp>
 #include <boost/throw_exception.hpp>
+#include <cstddef>
+#include <cstdint>
+#include <ndn-cxx/data.hpp>
+#include <ndn-cxx/encoding/block.hpp>
+#include <ndn-cxx/face.hpp>
+#include <ndn-cxx/interest.hpp>
+#include <ndn-cxx/link.hpp>
+#include <ndn-cxx/lp/nack.hpp>
+#include <ndn-cxx/name.hpp>
+#include <ndn-cxx/security/key-chain.hpp>
+#include <ndn-cxx/security/v2/certificate.hpp>
 
 namespace ndn {
 namespace ndncert {
 
-using std::size_t;
 using boost::noncopyable;
-using std::shared_ptr;
-using std::unique_ptr;
-using std::weak_ptr;
-using std::make_shared;
-using ndn::make_unique;
-using std::enable_shared_from_this;
-using std::function;
-using std::bind;
-using ndn::Interest;
+using ndn::Block;
 using ndn::Data;
+using ndn::Interest;
+using ndn::make_unique;
 using ndn::Name;
 using ndn::PartialName;
-using ndn::Block;
 using ndn::time::system_clock;
 using ndn::time::toUnixTimestamp;
+using std::bind;
+using std::enable_shared_from_this;
+using std::function;
+using std::make_shared;
+using std::shared_ptr;
+using std::size_t;
+using std::unique_ptr;
+using std::weak_ptr;
 
 enum : uint32_t {
   tlv_ca_prefix = 129,
@@ -81,6 +79,7 @@
   tlv_parameter_value = 135,
   tlv_ca_certificate = 137,
   tlv_max_validity_period = 139,
+  tlv_max_suffix_length = 177,
   tlv_probe_response = 141,
   tlv_allow_longer_name = 143,
   tlv_ecdh_pub = 145,
@@ -99,7 +98,6 @@
   tlv_error_code = 171,
   tlv_error_info = 173,
   tlv_authentication_tag = 175,
-  tlv_max_suffix_length = 177,
   tlv_cert_to_revoke = 179
 };
 
@@ -111,8 +109,9 @@
 const std::string CONFIG_PROBE_PARAMETER = "probe-parameter-key";
 const std::string CONFIG_SUPPORTED_CHALLENGES = "supported-challenges";
 const std::string CONFIG_CHALLENGE = "challenge";
+const std::string CONFIG_MAX_SUFFIX_LENGTH = "max-suffix-length";
 
-// JSON format for Certificate Issuer (CA)
+// // JSON format for Certificate Issuer (CA)
 const std::string JSON_CA_NAME = "name";
 const std::string JSON_CA_CONFIG = "ca-config";
 const std::string JSON_CA_ECDH = "ecdh-pub";
@@ -123,13 +122,13 @@
 const std::string JSON_CA_CHALLENGE_ID = "challenge-id";
 const std::string JSON_CA_CERT_ID = "certificate-id";
 
-// JSON format for Challenge Module
+// // JSON format for Challenge Module
 const std::string JSON_CHALLENGE_STATUS = "challenge-status";
 const std::string JSON_CHALLENGE_REMAINING_TRIES = "remaining-tries";
 const std::string JSON_CHALLENGE_REMAINING_TIME = "remaining-time";
 const std::string JSON_CHALLENGE_ISSUED_CERT_NAME = "issued-cert-name";
 
-// JSON format for Certificate Requester
+// // JSON format for Certificate Requester
 const std::string JSON_CLIENT_PROBE_INFO = "probe-info";
 const std::string JSON_CLIENT_ECDH = "ecdh-pub";
 const std::string JSON_CLIENT_CERT_REQ = "cert-request";
@@ -137,14 +136,28 @@
 const std::string JSON_CLIENT_CERT_TO_REVOKE = "cert-to-revoke";
 
 // NDNCERT Status Enum
-enum {
-  STATUS_BEFORE_CHALLENGE = 0,
-  STATUS_CHALLENGE = 1,
-  STATUS_PENDING = 2,
-  STATUS_SUCCESS = 3,
-  STATUS_FAILURE = 4,
-  STATUS_NOT_STARTED = 5,
-  STATUS_ENDED = 6
+enum class Status : uint16_t {
+  BEFORE_CHALLENGE = 0,
+  CHALLENGE = 1,
+  PENDING = 2,
+  SUCCESS = 3,
+  FAILURE = 4,
+  NOT_STARTED = 5,
+  ENDED = 6
+};
+
+std::string statusToString(Status status);
+
+enum class Error : uint16_t {
+  BAD_INTEREST_FORMAT = 1,
+  BAD_PARAMETER_FORMAT = 2,
+  BAD_SIGNATURE = 3,
+  INVALID_PARAMETER = 4,
+  NAME_NOT_ALLOWED = 5,
+  BAD_VALIDITY_PERIOD = 6,
+  OUT_OF_TRIES = 7,
+  OUT_OF_TIME = 8,
+  NO_AVAILABLE_NAMES = 9
 };
 
 // Pre-defined challenge status
@@ -153,7 +166,7 @@
 const std::string CHALLENGE_STATUS_FAILURE_MAXRETRY = "failure-max-retry";
 const std::string CHALLENGE_STATUS_UNKNOWN_CHALLENGE = "unknown-challenge";
 
-} // namespace ndncert
-} // namespace ndn
+}  // namespace ndncert
+}  // namespace ndn
 
-#endif // NDNCERT_NDNCERT_COMMON_HPP
+#endif  // NDNCERT_NDNCERT_COMMON_HPP