crypto/secure_util.h

   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