diff --git a/include/mbedtls/hkdf.h b/include/mbedtls/hkdf.h
new file mode 100644
index 0000000..6833e72
--- /dev/null
+++ b/include/mbedtls/hkdf.h
@@ -0,0 +1,125 @@
+/**
+ * \file hkdf.h
+ *
+ * \brief   This file contains the HKDF interface.
+ *
+ *          The HMAC-based Extract-and-Expand Key Derivation Function (HKDF) is
+ *          specified by RFC 5869.
+ */
+/*
+ * Copyright (C) 2016-2018, ARM Limited, All Rights Reserved
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * This file is part of mbed TLS (https://tls.mbed.org)
+ */
+#ifndef MBEDTLS_HKDF_H
+#define MBEDTLS_HKDF_H
+
+#include "md.h"
+
+/**
+ *  \name HKDF Error codes
+ *  \{
+ */
+#define MBEDTLS_ERR_HKDF_BAD_INPUT_DATA  -0x5F80  /**< Bad input parameters to function. */
+/* \} name */
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ *  \brief  This is the HMAC-based Extract-and-Expand Key Derivation Function
+ *          (HKDF).
+ *
+ *  \param  md        A hash function; md.size denotes the length of the hash
+ *                    function output in bytes.
+ *  \param  salt      An optional salt value (a non-secret random value);
+ *                    if the salt is not provided, a string of all zeros of
+ *                    md.size length is used as the salt.
+ *  \param  salt_len  The length in bytes of the optional \p salt.
+ *  \param  ikm       The input keying material.
+ *  \param  ikm_len   The length in bytes of \p ikm.
+ *  \param  info      An optional context and application specific information
+ *                    string. This can be a zero-length string.
+ *  \param  info_len  The length of \p info in bytes.
+ *  \param  okm       The output keying material of \p okm_len bytes.
+ *  \param  okm_len   The length of the output keying material in bytes. This
+ *                    must be less than or equal to 255 * md.size bytes.
+ *
+ *  \return 0 on success.
+ *  \return #MBEDTLS_ERR_HKDF_BAD_INPUT_DATA when the parameters are invalid.
+ *  \return An MBEDTLS_ERR_MD_* error for errors returned from the underlying
+ *          MD layer.
+ */
+int mbedtls_hkdf( const mbedtls_md_info_t *md, const unsigned char *salt,
+                  size_t salt_len, const unsigned char *ikm, size_t ikm_len,
+                  const unsigned char *info, size_t info_len,
+                  unsigned char *okm, size_t okm_len );
+
+/**
+ *  \brief  Take the input keying material \p ikm and extract from it a
+ *          fixed-length pseudorandom key \p prk.
+ *
+ *  \param       md        A hash function; md.size denotes the length of the
+ *                         hash function output in bytes.
+ *  \param       salt      An optional salt value (a non-secret random value);
+ *                         if the salt is not provided, a string of all zeros
+ *                         of md.size length is used as the salt.
+ *  \param       salt_len  The length in bytes of the optional \p salt.
+ *  \param       ikm       The input keying material.
+ *  \param       ikm_len   The length in bytes of \p ikm.
+ *  \param[out]  prk       A pseudorandom key of at least md.size bytes.
+ *
+ *  \return 0 on success.
+ *  \return #MBEDTLS_ERR_HKDF_BAD_INPUT_DATA when the parameters are invalid.
+ *  \return An MBEDTLS_ERR_MD_* error for errors returned from the underlying
+ *          MD layer.
+ */
+int mbedtls_hkdf_extract( const mbedtls_md_info_t *md,
+                          const unsigned char *salt, size_t salt_len,
+                          const unsigned char *ikm, size_t ikm_len,
+                          unsigned char *prk );
+
+/**
+ *  \brief  Expand the supplied \p prk into several additional pseudorandom
+ *          keys, which is the output of the HKDF.
+ *
+ *  \param  md        A hash function; md.size denotes the length of the hash
+ *                    function output in bytes.
+ *  \param  prk       A pseudorandom key of at least md.size bytes. \p prk is usually,
+ *                    the output from the HKDF extract step.
+ *  \param  prk_len   The length in bytes of \p prk.
+ *  \param  info      An optional context and application specific information
+ *                    string. This can be a zero-length string.
+ *  \param  info_len  The length of \p info in bytes.
+ *  \param  okm       The output keying material of \p okm_len bytes.
+ *  \param  okm_len   The length of the output keying material in bytes. This
+ *                    must be less than or equal to 255 * md.size bytes.
+ *
+ *  \return 0 on success.
+ *  \return #MBEDTLS_ERR_HKDF_BAD_INPUT_DATA when the parameters are invalid.
+ *  \return An MBEDTLS_ERR_MD_* error for errors returned from the underlying
+ *          MD layer.
+ */
+int mbedtls_hkdf_expand( const mbedtls_md_info_t *md, const unsigned char *prk,
+                         size_t prk_len, const unsigned char *info,
+                         size_t info_len, unsigned char *okm, size_t okm_len );
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* hkdf.h */