1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4 
5 #ifndef CRYPTO_SECURE_UTIL_H_
6 #define CRYPTO_SECURE_UTIL_H_
7 
8 #include <stddef.h>
9 
10 #include "crypto/crypto_export.h"
11 
12 namespace crypto {
13 
14 // Performs a constant-time comparison of two strings, returning true if the
15 // strings are equal.
16 //
17 // For cryptographic operations, comparison functions such as memcmp() may
18 // expose side-channel information about input, allowing an attacker to
19 // perform timing analysis to determine what the expected bits should be. In
20 // order to avoid such attacks, the comparison must execute in constant time,
21 // so as to not to reveal to the attacker where the difference(s) are.
22 // For an example attack, see
23 // http://groups.google.com/group/keyczar-discuss/browse_thread/thread/5571eca0948b2a13
24 CRYPTO_EXPORT bool SecureMemEqual(const void* s1, const void* s2, size_t n);
25 
26 }  // namespace crypto
27 
28 #endif  // CRYPTO_SECURE_UTIL_H_
29 
30