diff --git a/library/constant_time.h b/library/constant_time.h
new file mode 100644
index 0000000..e14232b
--- /dev/null
+++ b/library/constant_time.h
@@ -0,0 +1,30 @@
+/**
+ *  Constant-time functions
+ *
+ *  Copyright The Mbed TLS Contributors
+ *  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.
+ */
+
+#include "common.h"
+
+#include <stddef.h>
+
+int mbedtls_ssl_safer_memcmp( const void *a, const void *b, size_t n );
+
+int mbedtls_constant_time_memcmp( const void *v1, const void *v2, size_t len );
+
+unsigned char mbedtls_nist_kw_safer_memcmp( const void *a, const void *b, size_t n );
+
+int mbedtls_safer_memcmp( const void *a, const void *b, size_t n );