diff --git a/library/hkdf.c b/library/hkdf.c
new file mode 100644
index 0000000..ded555c
--- /dev/null
+++ b/library/hkdf.c
@@ -0,0 +1,164 @@
+/*
+ *  HKDF implementation -- RFC 5869
+ *
+ *  Copyright (C) 2016-2017, 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)
+ */
+#if !defined(MBEDTLS_CONFIG_FILE)
+#include "mbedtls/config.h"
+#else
+#include MBEDTLS_CONFIG_FILE
+#endif
+
+#if defined(MBEDTLS_HKDF_C)
+
+#include <string.h>
+#include "mbedtls/hkdf.h"
+#include "mbedtls/platform_util.h"
+
+/* HKDF-Extract + HKDF-Expand */
+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 )
+{
+    int ret;
+    unsigned char prk[MBEDTLS_MD_MAX_SIZE];
+
+    ret = mbedtls_hkdf_extract( md, salt, salt_len, ikm, ikm_len, prk );
+
+    if ( ret == 0 ) {
+        ret = mbedtls_hkdf_expand( md, prk, mbedtls_md_get_size(md), info, info_len, okm, okm_len );
+    }
+
+    mbedtls_platform_zeroize( prk, sizeof( prk ) );
+
+    return( ret );
+}
+
+/* HKDF-Extract(salt, IKM) -> PRK */
+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 )
+{
+    unsigned char null_salt[MBEDTLS_MD_MAX_SIZE] = { '\0' };
+
+    if ( salt == NULL ) {
+        size_t hash_len;
+
+        hash_len = mbedtls_md_get_size( md );
+
+        if ( hash_len == 0 ) {
+            return MBEDTLS_ERR_HKDF_BAD_PARAM;
+        }
+
+        salt = null_salt;
+        salt_len = hash_len;
+    }
+
+    return( mbedtls_md_hmac( md, salt, salt_len, ikm, ikm_len, prk ) );
+}
+
+/* HKDF-Expand(PRK, info, L) -> OKM */
+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 )
+{
+    size_t hash_len;
+    size_t where = 0;
+    size_t N;
+    size_t T_len = 0;
+    size_t i;
+    int ret = 0;
+    mbedtls_md_context_t ctx;
+    unsigned char T[MBEDTLS_MD_MAX_SIZE];
+
+    if ( okm == NULL ) {
+        return( MBEDTLS_ERR_HKDF_BAD_PARAM );
+    }
+
+    hash_len = mbedtls_md_get_size(md);
+
+    if ( (prk_len < hash_len) || (hash_len == 0) ) {
+        return( MBEDTLS_ERR_HKDF_BAD_PARAM );
+    }
+
+    if ( info == NULL ) {
+        info = (const unsigned char *) "";
+        info_len = 0;
+    }
+
+    N = okm_len / hash_len;
+
+    if ( (okm_len % hash_len) != 0 ) {
+        N++;
+    }
+
+    if ( N > 255 ) {
+        return( MBEDTLS_ERR_HKDF_BAD_PARAM );
+    }
+
+    mbedtls_md_init( &ctx );
+
+    if ( (ret = mbedtls_md_setup( &ctx, md, 1) ) != 0 ) {
+        goto exit;
+    }
+
+    /* Section 2.3. */
+    for ( i = 1; i <= N; i++ ) {
+        unsigned char c = i & 0xff;
+
+        ret = mbedtls_md_hmac_starts( &ctx, prk, prk_len );
+        if ( ret != 0 ) {
+            goto exit;
+        }
+
+        ret = mbedtls_md_hmac_update( &ctx, T, T_len );
+        if ( ret != 0 ) {
+            goto exit;
+        }
+
+        ret = mbedtls_md_hmac_update( &ctx, info, info_len );
+        if ( ret != 0 ) {
+            goto exit;
+        }
+
+        /* The constant concatenated to the end of each T(n) is a single octet.
+         * */
+        ret = mbedtls_md_hmac_update( &ctx, &c, 1 );
+        if ( ret != 0 ) {
+            goto exit;
+        }
+
+        ret = mbedtls_md_hmac_finish( &ctx, T );
+        if ( ret != 0 ) {
+            goto exit;
+        }
+
+        memcpy( okm + where, T, (i != N) ? hash_len : (okm_len - where) );
+        where += hash_len;
+        T_len = hash_len;
+    }
+
+exit:
+    mbedtls_md_free( &ctx );
+
+    return( ret );
+}
+
+#endif /* MBEDTLS_HKDF_C */