1 files changed, 20 insertions, 0 deletions
diff --git a/board/cr50/dcrypto/compare.c b/board/cr50/dcrypto/compare.c
new file mode 100644
index 0000000000..db6193752b
--- /dev/null
+++ b/board/cr50/dcrypto/compare.c
@@ -0,0 +1,20 @@
+/* Copyright 2016 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "dcrypto.h"
+
+/* Constant time comparator. */
+int DCRYPTO_equals(const void *a, const void *b, size_t len)
+{
+	size_t i;
+	const uint8_t *pa = a;
+	const uint8_t *pb = b;
+	uint8_t diff = 0;
+
+	for (i = 0; i < len; i++)
+		diff |= pa[i] ^ pb[i];
+
+	return !diff;
+}