diff --git a/src/detail/crypto-helpers.cpp b/src/detail/crypto-helpers.cpp
new file mode 100644
index 0000000..2437d16
--- /dev/null
+++ b/src/detail/crypto-helpers.cpp
@@ -0,0 +1,369 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/**
+ * Copyright (c) 2017-2020, Regents of the University of California.
+ *
+ * This file is part of ndncert, a certificate management system based on NDN.
+ *
+ * ndncert is free software: you can redistribute it and/or modify it under the terms
+ * of the GNU General Public License as published by the Free Software Foundation, either
+ * version 3 of the License, or (at your option) any later version.
+ *
+ * ndncert is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+ * PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received copies of the GNU General Public License along with
+ * ndncert, e.g., in COPYING.md file.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * See AUTHORS.md for complete list of ndncert authors and contributors.
+ */
+
+#include "crypto-helpers.hpp"
+
+#include <boost/endian/conversion.hpp>
+#include <cmath>
+#include <ndn-cxx/encoding/buffer-stream.hpp>
+#include <ndn-cxx/security/transform/base64-decode.hpp>
+#include <ndn-cxx/security/transform/base64-encode.hpp>
+#include <ndn-cxx/security/transform/buffer-source.hpp>
+#include <ndn-cxx/security/transform/stream-sink.hpp>
+#include <ndn-cxx/util/random.hpp>
+#include <openssl/ec.h>
+#include <openssl/err.h>
+#include <openssl/evp.h>
+#include <openssl/hmac.h>
+#include <openssl/kdf.h>
+#include <openssl/pem.h>
+
+namespace ndn {
+namespace ndncert {
+
+struct ECDHState::ECDH_CTX
+{
+  ~ECDH_CTX()
+  {
+    // Contexts
+    if (ctx_params != nullptr) {
+      EVP_PKEY_CTX_free(ctx_params);
+    }
+    if (ctx_keygen != nullptr) {
+      EVP_PKEY_CTX_free(ctx_keygen);
+    }
+    // Keys
+    if (privkey != nullptr) {
+      EVP_PKEY_free(privkey);
+    }
+    if (peerkey != nullptr) {
+      EVP_PKEY_free(peerkey);
+    }
+    if (params != nullptr) {
+      EVP_PKEY_free(params);
+    }
+  }
+  EVP_PKEY_CTX* ctx_params = nullptr;
+  EVP_PKEY_CTX* ctx_keygen = nullptr;
+  EVP_PKEY* privkey = nullptr;
+  EVP_PKEY* peerkey = nullptr;
+  EVP_PKEY* params = nullptr;
+};
+
+ECDHState::ECDHState()
+{
+  context = std::make_unique<ECDH_CTX>();
+  auto EC_NID = NID_X9_62_prime256v1;
+
+  if (nullptr == (context->ctx_params = EVP_PKEY_CTX_new_id(EVP_PKEY_EC, nullptr))) {
+    NDN_THROW(std::runtime_error("Could not create context."));
+  }
+  if (EVP_PKEY_paramgen_init(context->ctx_params) != 1) {
+    context.reset();
+    NDN_THROW(std::runtime_error("Could not initialize parameter generation."));
+  }
+  if (1 != EVP_PKEY_CTX_set_ec_paramgen_curve_nid(context->ctx_params, EC_NID)) {
+    context.reset();
+    NDN_THROW(std::runtime_error("Likely unknown elliptical curve ID specified."));
+  }
+  if (!EVP_PKEY_paramgen(context->ctx_params, &context->params)) {
+    context.reset();
+    NDN_THROW(std::runtime_error("Could not create parameter object parameters."));
+  }
+  if (nullptr == (context->ctx_keygen = EVP_PKEY_CTX_new(context->params, nullptr))) {
+    context.reset();
+    NDN_THROW(std::runtime_error("Could not create the context for the key generation"));
+  }
+  if (1 != EVP_PKEY_keygen_init(context->ctx_keygen)) {
+    context.reset();
+    NDN_THROW(std::runtime_error("Could not init context for key generation."));
+  }
+  if (1 != EVP_PKEY_keygen(context->ctx_keygen, &context->privkey)) {
+    context.reset();
+    NDN_THROW(std::runtime_error("Could not generate DHE keys in final step"));
+  }
+}
+
+ECDHState::~ECDHState()
+{}
+
+uint8_t*
+ECDHState::getRawSelfPubKey()
+{
+  auto privECKey = EVP_PKEY_get1_EC_KEY(context->privkey);
+  if (privECKey == nullptr) {
+    context.reset();
+    NDN_THROW(std::runtime_error("Could not get key when calling EVP_PKEY_get1_EC_KEY()."));
+  }
+  auto ecPoint = EC_KEY_get0_public_key(privECKey);
+  const EC_GROUP* group = EC_KEY_get0_group(privECKey);
+  m_publicKeyLen = EC_POINT_point2oct(group, ecPoint, POINT_CONVERSION_COMPRESSED,
+                                      m_publicKey, 256, nullptr);
+  EC_KEY_free(privECKey);
+  if (m_publicKeyLen == 0) {
+    context.reset();
+    NDN_THROW(std::runtime_error("Could not convert EC_POINTS to octet string when calling EC_POINT_point2oct."));
+  }
+  return m_publicKey;
+}
+
+std::string
+ECDHState::getBase64PubKey()
+{
+  if (m_publicKeyLen == 0) {
+    this->getRawSelfPubKey();
+  }
+  std::ostringstream os;
+  namespace t = ndn::security::transform;
+  t::bufferSource(m_publicKey, m_publicKeyLen) >> t::base64Encode(false) >> t::streamSink(os);
+  return os.str();
+}
+
+uint8_t*
+ECDHState::deriveSecret(const uint8_t* peerkey, size_t peerKeySize)
+{
+  auto privECKey = EVP_PKEY_get1_EC_KEY(context->privkey);
+  if (privECKey == nullptr) {
+    context.reset();
+    NDN_THROW(std::runtime_error("Could not get key when calling EVP_PKEY_get1_EC_KEY()"));
+  }
+  auto group = EC_KEY_get0_group(privECKey);
+  auto peerPoint = EC_POINT_new(group);
+  int result = EC_POINT_oct2point(group, peerPoint, peerkey, peerKeySize, nullptr);
+  if (result == 0) {
+    EC_POINT_free(peerPoint);
+    EC_KEY_free(privECKey);
+    context.reset();
+    NDN_THROW(std::runtime_error("Cannot convert peer's key into a EC point when calling EC_POINT_oct2point()"));
+  }
+  result = ECDH_compute_key(m_sharedSecret, 256, peerPoint, privECKey, nullptr);
+  if (result == -1) {
+    EC_POINT_free(peerPoint);
+    EC_KEY_free(privECKey);
+    context.reset();
+    NDN_THROW(std::runtime_error("Cannot generate ECDH secret when calling ECDH_compute_key()"));
+  }
+  m_sharedSecretLen = static_cast<size_t>(result);
+  EC_POINT_free(peerPoint);
+  EC_KEY_free(privECKey);
+  return m_sharedSecret;
+}
+
+uint8_t*
+ECDHState::deriveSecret(const std::string& peerKeyStr)
+{
+  namespace t = ndn::security::transform;
+  OBufferStream os;
+  t::bufferSource(peerKeyStr) >> t::base64Decode(false) >> t::streamSink(os);
+  auto result = os.buf();
+  return this->deriveSecret(result->data(), result->size());
+}
+
+void
+hmac_sha256(const uint8_t* data, size_t data_length,
+            const uint8_t* key, size_t key_length,
+            uint8_t* result)
+{
+  auto ret = HMAC(EVP_sha256(), key, key_length, (unsigned char*)data, data_length,
+                  (unsigned char*)result, nullptr);
+  if (ret == nullptr) {
+    NDN_THROW(std::runtime_error("Error computing HMAC when calling HMAC()"));
+  }
+}
+
+int
+hkdf(const uint8_t* secret, size_t secret_len, const uint8_t* salt,
+     size_t salt_len, uint8_t* output, size_t output_len,
+     const uint8_t* info, size_t info_len)
+{
+  EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_HKDF, nullptr);
+  if (EVP_PKEY_derive_init(pctx) <= 0) {
+    EVP_PKEY_CTX_free(pctx);
+    NDN_THROW(std::runtime_error("HKDF: Cannot init ctx when calling EVP_PKEY_derive_init()."));
+  }
+  if (EVP_PKEY_CTX_set_hkdf_md(pctx, EVP_sha256()) <= 0) {
+    EVP_PKEY_CTX_free(pctx);
+    NDN_THROW(std::runtime_error("HKDF: Cannot set md when calling EVP_PKEY_CTX_set_hkdf_md()."));
+  }
+  if (EVP_PKEY_CTX_set1_hkdf_salt(pctx, salt, salt_len) <= 0) {
+    EVP_PKEY_CTX_free(pctx);
+    NDN_THROW(std::runtime_error("HKDF: Cannot set salt when calling EVP_PKEY_CTX_set1_hkdf_salt()."));
+  }
+  if (EVP_PKEY_CTX_set1_hkdf_key(pctx, secret, secret_len) <= 0) {
+    EVP_PKEY_CTX_free(pctx);
+    NDN_THROW(std::runtime_error("HKDF: Cannot set secret when calling EVP_PKEY_CTX_set1_hkdf_key()."));
+  }
+  if (EVP_PKEY_CTX_add1_hkdf_info(pctx, info, info_len) <= 0) {
+    EVP_PKEY_CTX_free(pctx);
+    NDN_THROW(std::runtime_error("HKDF: Cannot set info when calling EVP_PKEY_CTX_add1_hkdf_info()."));
+  }
+  size_t outLen = output_len;
+  if (EVP_PKEY_derive(pctx, output, &outLen) <= 0) {
+    EVP_PKEY_CTX_free(pctx);
+    NDN_THROW(std::runtime_error("HKDF: Cannot derive result when calling EVP_PKEY_derive()."));
+  }
+  EVP_PKEY_CTX_free(pctx);
+  return (int)outLen;
+}
+
+int
+aes_gcm_128_encrypt(const uint8_t* plaintext, size_t plaintext_len, const uint8_t* associated, size_t associated_len,
+                    const uint8_t* key, const uint8_t* iv, uint8_t* ciphertext, uint8_t* tag)
+{
+  EVP_CIPHER_CTX* ctx;
+  int len;
+  int ciphertext_len;
+  if (!(ctx = EVP_CIPHER_CTX_new())) {
+    NDN_THROW(std::runtime_error("Cannot create and initialise the context when calling EVP_CIPHER_CTX_new()"));
+  }
+  if (1 != EVP_EncryptInit_ex(ctx, EVP_aes_128_gcm(), nullptr, nullptr, nullptr)) {
+    EVP_CIPHER_CTX_free(ctx);
+    NDN_THROW(std::runtime_error("Cannot initialise the encryption operation when calling EVP_EncryptInit_ex()"));
+  }
+  if (1 != EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_SET_IVLEN, 12, nullptr)) {
+    EVP_CIPHER_CTX_free(ctx);
+    NDN_THROW(std::runtime_error("Cannot set IV length when calling EVP_CIPHER_CTX_ctrl()"));
+  }
+  if (1 != EVP_EncryptInit_ex(ctx, nullptr, nullptr, key, iv)) {
+    EVP_CIPHER_CTX_free(ctx);
+    NDN_THROW(std::runtime_error("Cannot initialize key and IV when calling EVP_EncryptInit_ex()"));
+  }
+  if (1 != EVP_EncryptUpdate(ctx, nullptr, &len, associated, associated_len)) {
+    EVP_CIPHER_CTX_free(ctx);
+    NDN_THROW(std::runtime_error("Cannot set associated authentication data when calling EVP_EncryptUpdate()"));
+  }
+  if (1 != EVP_EncryptUpdate(ctx, ciphertext, &len, plaintext, plaintext_len)) {
+    EVP_CIPHER_CTX_free(ctx);
+    NDN_THROW(std::runtime_error("Cannot encrypt when calling EVP_EncryptUpdate()"));
+  }
+  ciphertext_len = len;
+  if (1 != EVP_EncryptFinal_ex(ctx, ciphertext + len, &len)) {
+    EVP_CIPHER_CTX_free(ctx);
+    NDN_THROW(std::runtime_error("Cannot finalise the encryption when calling EVP_EncryptFinal_ex()"));
+  }
+  ciphertext_len += len;
+  if (1 != EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_GET_TAG, 16, tag)) {
+    EVP_CIPHER_CTX_free(ctx);
+    NDN_THROW(std::runtime_error("Cannot get tag when calling EVP_CIPHER_CTX_ctrl()"));
+  }
+  EVP_CIPHER_CTX_free(ctx);
+  return ciphertext_len;
+}
+
+int
+aes_gcm_128_decrypt(const uint8_t* ciphertext, size_t ciphertext_len, const uint8_t* associated, size_t associated_len,
+                    const uint8_t* tag, const uint8_t* key, const uint8_t* iv, uint8_t* plaintext)
+{
+  EVP_CIPHER_CTX* ctx;
+  int len;
+  int plaintext_len;
+  int ret;
+  if (!(ctx = EVP_CIPHER_CTX_new())) {
+    NDN_THROW(std::runtime_error("Cannot create and initialise the context when calling EVP_CIPHER_CTX_new()"));
+  }
+  if (!EVP_DecryptInit_ex(ctx, EVP_aes_128_gcm(), nullptr, nullptr, nullptr)) {
+    EVP_CIPHER_CTX_free(ctx);
+    NDN_THROW(std::runtime_error("Cannot initialise the decryption operation when calling EVP_DecryptInit_ex()"));
+  }
+  if (!EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_SET_IVLEN, 12, nullptr)) {
+    EVP_CIPHER_CTX_free(ctx);
+    NDN_THROW(std::runtime_error("Cannot set IV length when calling EVP_CIPHER_CTX_ctrl"));
+  }
+  if (!EVP_DecryptInit_ex(ctx, nullptr, nullptr, key, iv)) {
+    EVP_CIPHER_CTX_free(ctx);
+    NDN_THROW(std::runtime_error("Cannot initialise key and IV when calling EVP_DecryptInit_ex()"));
+  }
+  if (!EVP_DecryptUpdate(ctx, nullptr, &len, associated, associated_len)) {
+    EVP_CIPHER_CTX_free(ctx);
+    NDN_THROW(std::runtime_error("Cannot set associated authentication data when calling EVP_EncryptUpdate()"));
+  }
+  if (!EVP_DecryptUpdate(ctx, plaintext, &len, ciphertext, ciphertext_len)) {
+    EVP_CIPHER_CTX_free(ctx);
+    NDN_THROW(std::runtime_error("Cannot decrypt when calling EVP_DecryptUpdate()"));
+  }
+  plaintext_len = len;
+  if (!EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_SET_TAG, 16, (void*)tag)) {
+    EVP_CIPHER_CTX_free(ctx);
+    NDN_THROW(std::runtime_error("Cannot set tag value when calling EVP_CIPHER_CTX_ctrl"));
+  }
+  // Finalise the decryption. A positive return value indicates success,
+  // anything else is a failure - the plaintext is not trustworthy.
+  ret = EVP_DecryptFinal_ex(ctx, plaintext + len, &len);
+  // Clean up
+  EVP_CIPHER_CTX_free(ctx);
+  if (ret > 0) {
+    // Success
+    plaintext_len += len;
+    return plaintext_len;
+  }
+  else {
+    // Verify failed
+    return -1;
+  }
+}
+
+Block
+encodeBlockWithAesGcm128(uint32_t tlv_type, const uint8_t* key, const uint8_t* payload, size_t payloadSize,
+                         const uint8_t* associatedData, size_t associatedDataSize, uint32_t& counter)
+{
+  Buffer iv(12);
+  random::generateSecureBytes(iv.data(), iv.size());
+  if (tlv_type == ndn::tlv::ApplicationParameters) {
+    // requester
+    iv[0] &= ~(1UL << 7);
+  }
+  else {
+    // CA
+    iv[0] |= 1UL << 7;
+  }
+  uint32_t temp = counter;
+  boost::endian::native_to_big_inplace(temp);
+  std::memcpy(&iv[8], reinterpret_cast<const uint8_t*>(&temp), 4);
+  counter += std::ceil(payloadSize / 8);
+
+  Buffer encryptedPayload(payloadSize);
+  uint8_t tag[16];
+  size_t encryptedPayloadLen = aes_gcm_128_encrypt(payload, payloadSize, associatedData, associatedDataSize,
+                                                   key, iv.data(), encryptedPayload.data(), tag);
+  auto content = makeEmptyBlock(tlv_type);
+  content.push_back(makeBinaryBlock(tlv::InitializationVector, iv.data(), iv.size()));
+  content.push_back(makeBinaryBlock(tlv::AuthenticationTag, tag, 16));
+  content.push_back(makeBinaryBlock(tlv::EncryptedPayload, encryptedPayload.data(), encryptedPayloadLen));
+  content.encode();
+  return content;
+}
+
+Buffer
+decodeBlockWithAesGcm128(const Block& block, const uint8_t* key, const uint8_t* associatedData, size_t associatedDataSize)
+{
+  block.parse();
+  Buffer result(block.get(tlv::EncryptedPayload).value_size());
+  int resultLen = aes_gcm_128_decrypt(block.get(tlv::EncryptedPayload).value(),
+                                      block.get(tlv::EncryptedPayload).value_size(),
+                                      associatedData, associatedDataSize, block.get(tlv::AuthenticationTag).value(),
+                                      key, block.get(tlv::InitializationVector).value(), result.data());
+  if (resultLen == -1 || resultLen != (int)block.get(tlv::EncryptedPayload).value_size()) {
+    return Buffer();
+  }
+  return result;
+}
+
+} // namespace ndncert
+} // namespace ndn