diff --git a/tools/ndnsec-cert-gen.hpp b/tools/ndnsec-cert-gen.hpp
new file mode 100644
index 0000000..023df7e
--- /dev/null
+++ b/tools/ndnsec-cert-gen.hpp
@@ -0,0 +1,271 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil -*- */
+/*
+ * Copyright (c) 2013, Regents of the University of California
+ * BSD license, See the LICENSE file for more information
+ * Author: Yingdi Yu <yingdi@cs.ucla.edu>
+ */
+
+#ifndef NDNSEC_CERT_GEN_HPP
+#define NDNSEC_CERT_GEN_HPP
+
+#include "ndnsec-util.hpp"
+
+int 
+ndnsec_cert_gen(int argc, char** argv)
+{
+  using boost::tokenizer;
+  using boost::escaped_list_separator;
+
+  using namespace ndn;
+  namespace po = boost::program_options;
+
+  typedef boost::posix_time::ptime Time;
+  
+  std::string notBeforeStr;
+  std::string notAfterStr;
+  std::string sName;
+  std::string reqFile;
+  std::string signId;
+  std::string subInfo;
+  bool isSelfSigned = false;
+  bool nack = false;
+
+  po::options_description desc("General Usage\n  ndnsec cert-gen [-h] [-S date] [-E date] [-N subject-name] [-I subject-info] [-s sign-id] request\nGeneral options");
+  desc.add_options()
+    ("help,h", "produce help message")
+    ("not-before,S", po::value<std::string>(&notBeforeStr), "certificate starting date, YYYYMMDDhhmmss")
+    ("not-after,E", po::value<std::string>(&notAfterStr), "certificate ending date, YYYYMMDDhhmmss")
+    ("subject-name,N", po::value<std::string>(&sName), "subject name")
+    ("subject-info,I", po::value<std::string>(&subInfo), "subject info, pairs of OID and string description: \"2.5.4.10 'University of California, Los Angeles'\"")
+    ("nack", "Generate revocation certificate (NACK)")
+    ("sign-id,s", po::value<std::string>(&signId), "signing Identity, self-signed if not specified")
+    ("request,r", po::value<std::string>(&reqFile), "request file name, - for stdin")
+    ;
+
+  po::positional_options_description p;
+  p.add("request", 1);
+
+  po::variables_map vm;
+  try
+    {
+      po::store(po::command_line_parser(argc, argv).options(desc).positional(p).run(), vm);
+      po::notify(vm);
+    }
+  catch (std::exception &e)
+    {
+      std::cerr << "ERROR: " << e.what() << std::endl;
+      return 1;
+    }
+
+  if (vm.count("help"))
+    {
+      std::cerr << desc << std::endl;
+      return 0;
+    }
+
+  if (0 == vm.count("sign-id"))
+    {     
+      isSelfSigned = true;
+    }
+
+  if (vm.count("nack"))
+    {
+      nack = true;
+    }
+
+  std::vector<CertificateSubjectDescription> otherSubDescrypt;
+  tokenizer<escaped_list_separator<char> > subInfoItems(subInfo, escaped_list_separator<char> ("\\", " \t", "'\""));
+
+  tokenizer<escaped_list_separator<char> >::iterator it = subInfoItems.begin();
+  try
+    {
+      while (it != subInfoItems.end())
+        {
+          std::string oid = *it;
+
+          it++;
+          if (it == subInfoItems.end ())
+            {
+              std::cerr << "ERROR: unmatched info for oid [" << oid << "]" << std::endl;
+              return 1;
+            }
+
+          std::string value = *it;
+
+          otherSubDescrypt.push_back (CertificateSubjectDescription(oid, value));
+
+          it++;
+        }
+    }
+  catch (std::exception &e)
+    {
+      std::cerr << "error in parsing subject info" << std::endl;
+      return 1;
+    }
+
+  Time notBefore;
+  Time notAfter;
+  try{
+    if (0 == vm.count("not-before"))
+      {
+        notBefore = boost::posix_time::second_clock::universal_time();
+      }
+    else
+      {
+        notBefore = boost::posix_time::from_iso_string(notBeforeStr.substr(0, 8) + "T" + notBeforeStr.substr(8, 6));
+      }
+
+
+    if (0 == vm.count("not-after"))
+      {
+        notAfter = notBefore + boost::posix_time::hours(24*365);
+      }
+    else
+      {
+        notAfter = boost::posix_time::from_iso_string(notAfterStr.substr(0, 8) + "T" + notAfterStr.substr(8, 6));
+        if(notAfter < notBefore)
+          {
+            std::cerr << "not-before is later than not-after" << std::endl;
+            return 1;
+          }
+      }
+  }catch(std::exception & e){
+    std::cerr << "Error in converting validity timestamp!" << std::endl;
+    return 1;
+  }
+
+  if (0 == vm.count("request"))
+    {
+      std::cerr << "request file must be specified" << std::endl;
+      return 1;
+    }
+
+  shared_ptr<IdentityCertificate> selfSignedCertificate = getIdentityCertificate(reqFile);
+  if(!static_cast<bool>(selfSignedCertificate))
+    {
+      std::cerr << "ERROR: input error" << std::endl;
+      return 1;
+    }
+
+  Name keyName = selfSignedCertificate->getPublicKeyName();
+  Name signIdName;
+  Name certName;
+
+  if(isSelfSigned)
+    {
+      certName = keyName.getPrefix(keyName.size()-1);
+      certName.append("KEY").append(keyName.get(-1)).append("ID-CERT").appendVersion();
+    }
+  else
+    {
+      signIdName = Name(signId);
+  
+      Name::const_iterator i = keyName.begin();
+      Name::const_iterator j = signIdName.begin();
+      int count = 0;
+      for(; i != keyName.end() && j != signIdName.end(); i++, j++, count++)
+        {
+          if(*i != *j)
+            break;
+        }
+      
+      if(j != signIdName.end() || i == keyName.end())
+        {
+          std::cerr << "wrong signing identity!" << std::endl;
+          return 1;
+        }
+
+      certName = keyName.getSubName(0, count);
+      certName.append("KEY").append(keyName.getSubName(count, keyName.size()-count));
+      certName.append("ID-CERT").appendVersion ();
+    }
+
+  Block wire;
+
+  if (!nack)
+    {
+      if (0 == vm.count("subject-name"))
+        {
+          std::cerr << "subject_name must be specified" << std::endl;
+          return 1;
+        }
+
+      try
+        {
+          CertificateSubjectDescription subDescryptName("2.5.4.41", sName);
+          IdentityCertificate certificate;
+          certificate.setName(certName);
+          certificate.setNotBefore((notBefore-ndn::UNIX_EPOCH_TIME).total_milliseconds());
+          certificate.setNotAfter((notAfter-ndn::UNIX_EPOCH_TIME).total_milliseconds());
+          certificate.setPublicKeyInfo(selfSignedCertificate->getPublicKeyInfo());
+          certificate.addSubjectDescription(subDescryptName);
+          for(int i = 0; i < otherSubDescrypt.size(); i++)
+            certificate.addSubjectDescription(otherSubDescrypt[i]);
+          certificate.encode();
+
+          KeyChain keyChain;
+
+          if(isSelfSigned)
+            keyChain.selfSign(certificate);
+          else
+            {
+              Name signingCertificateName = keyChain.getDefaultCertificateNameForIdentity(Name(signId));
+              
+              keyChain.sign(certificate, signingCertificateName);
+            }
+          wire = certificate.wireEncode();
+        }
+      catch(SecPublicInfo::Error& e)
+        {
+          std::cerr << "ERROR: " << e.what() << std::endl;
+          return 1;
+        }
+      catch(SecTpm::Error& e)
+        {
+          std::cerr << "ERROR: " << e.what() << std::endl;
+          return 1;
+        }
+    }
+  else
+    {
+      Data revocationCert;
+      // revocationCert.setContent(void*, 0); // empty content
+      revocationCert.setName(certName);
+
+      try
+        {
+          KeyChain keyChain;
+          
+          Name signingCertificateName = keyChain.getDefaultCertificateNameForIdentity(Name(signId));
+          
+          keyChain.sign (revocationCert, signingCertificateName);
+          wire = revocationCert.wireEncode();
+        }
+      catch(SecPublicInfo::Error& e)
+        {
+          std::cerr << "ERROR: " << e.what() << std::endl;
+          return 1;
+        }
+      catch(SecTpm::Error& e)
+        {
+          std::cerr << "ERROR: " << e.what() << std::endl;
+          return 1;
+        }
+    }
+
+  try
+    {
+      using namespace CryptoPP;
+      StringSource ss(wire.wire(), wire.size(), true,
+                      new Base64Encoder(new FileSink(std::cout), true, 64));
+    }
+  catch(CryptoPP::Exception& e)
+    {
+      std::cerr << "ERROR: " << e.what() << std::endl;
+      return 1;
+    }
+
+  return 0;
+}
+
+#endif //NDNSEC_CERT_GEN_HPP