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