diff --git a/drivers/auth/mbedtls/mbedtls_crypto.c b/drivers/auth/mbedtls/mbedtls_crypto.c
index 1a96e8f..11d3ede 100644
--- a/drivers/auth/mbedtls/mbedtls_crypto.c
+++ b/drivers/auth/mbedtls/mbedtls_crypto.c
@@ -217,7 +217,7 @@
 	}
 
 	/* Compare values */
-	rc = memcmp(data_hash, hash, mbedtls_md_get_size(md_info));
+	rc = timingsafe_bcmp(data_hash, hash, mbedtls_md_get_size(md_info));
 	if (rc != 0) {
 		return CRYPTO_ERR_HASH;
 	}
diff --git a/drivers/auth/mbedtls/mbedtls_x509_parser.c b/drivers/auth/mbedtls/mbedtls_x509_parser.c
index 73da9d1..f9485de 100644
--- a/drivers/auth/mbedtls/mbedtls_x509_parser.c
+++ b/drivers/auth/mbedtls/mbedtls_x509_parser.c
@@ -392,7 +392,7 @@
 	if (sig_alg1.len != sig_alg2.len) {
 		return IMG_PARSER_ERR_FORMAT;
 	}
-	if (0 != memcmp(sig_alg1.p, sig_alg2.p, sig_alg1.len)) {
+	if (0 != timingsafe_bcmp(sig_alg1.p, sig_alg2.p, sig_alg1.len)) {
 		return IMG_PARSER_ERR_FORMAT;
 	}
 	memcpy(&sig_alg, &sig_alg1, sizeof(sig_alg));
diff --git a/include/lib/stdlib/string.h b/include/lib/stdlib/string.h
index 61e8102..902d9c1 100644
--- a/include/lib/stdlib/string.h
+++ b/include/lib/stdlib/string.h
@@ -31,7 +31,7 @@
  */
 
 /*
- * Portions copyright (c) 2013-2014, ARM Limited and Contributors.
+ * Portions copyright (c) 2013-2017, ARM Limited and Contributors.
  * All rights reserved.
  */
 
@@ -59,7 +59,9 @@
 int	 strcmp(const char *, const char *) __pure;
 size_t	 strlen(const char *) __pure;
 int	 strncmp(const char *, const char *, size_t) __pure;
+size_t	 strnlen(const char *, size_t) __pure;
 int	 strcasecmp(const char *, const char *);
+int	 timingsafe_bcmp(const void *, const void *, size_t);
 
 __END_DECLS
 
diff --git a/lib/stdlib/stdlib.mk b/lib/stdlib/stdlib.mk
index cdf3d29..5332717 100644
--- a/lib/stdlib/stdlib.mk
+++ b/lib/stdlib/stdlib.mk
@@ -1,5 +1,5 @@
 #
-# Copyright (c) 2016, ARM Limited and Contributors. All rights reserved.
+# Copyright (c) 2016-2017, ARM Limited and Contributors. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are met:
@@ -41,7 +41,9 @@
 			strcmp.c			\
 			strlen.c			\
 			strncmp.c			\
-			subr_prf.c)
+			strnlen.c			\
+			subr_prf.c			\
+			timingsafe_bcmp.c)
 
 INCLUDES	+=	-Iinclude/lib/stdlib		\
 			-Iinclude/lib/stdlib/sys
diff --git a/lib/stdlib/strnlen.c b/lib/stdlib/strnlen.c
new file mode 100644
index 0000000..d48502b
--- /dev/null
+++ b/lib/stdlib/strnlen.c
@@ -0,0 +1,45 @@
+/*-
+ * Copyright (c) 2009 David Schultz <das@FreeBSD.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+/*
+ * Portions copyright (c) 2017, ARM Limited and Contributors. All rights reserved.
+ */
+
+#include <sys/cdefs.h>
+
+#include <string.h>
+
+size_t
+strnlen(const char *s, size_t maxlen)
+{
+	size_t len;
+
+	for (len = 0; len < maxlen; len++, s++) {
+		if (!*s)
+			break;
+	}
+	return (len);
+}
diff --git a/lib/stdlib/timingsafe_bcmp.c b/lib/stdlib/timingsafe_bcmp.c
new file mode 100644
index 0000000..d098158
--- /dev/null
+++ b/lib/stdlib/timingsafe_bcmp.c
@@ -0,0 +1,36 @@
+/*	$OpenBSD: timingsafe_bcmp.c,v 1.3 2015/08/31 02:53:57 guenther Exp $	*/
+/*
+ * Copyright (c) 2010 Damien Miller.  All rights reserved.
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <string.h>
+
+int __timingsafe_bcmp(const void *, const void *, size_t);
+
+int
+__timingsafe_bcmp(const void *b1, const void *b2, size_t n)
+{
+	const unsigned char *p1 = b1, *p2 = b2;
+	int ret = 0;
+
+	for (; n > 0; n--)
+		ret |= *p1++ ^ *p2++;
+	return (ret != 0);
+}
+
+__weak_reference(__timingsafe_bcmp, timingsafe_bcmp);