Added crypto random-number generator

base/rand_util.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_RAND_UTIL_H_
 #define BASE_RAND_UTIL_H_
 #pragma once
 
 #include <string>
 
@@ skipping 15 matching lines @@
 //   std::random_shuffle(myvector.begin(), myvector.end(), base::RandGenerator);
 BASE_EXPORT uint64 RandGenerator(uint64 range);
 
 // Returns a random double in range [0, 1). Thread-safe.
 BASE_EXPORT double RandDouble();
 
 // Given input |bits|, convert with maximum precision to a double in
 // the range [0, 1). Thread-safe.
 BASE_EXPORT double BitsToOpenEndedUnitInterval(uint64 bits);
 
-// Fills |output_length| bytes of |output| with cryptographically strong random
-// data.
+// Fills |output_length| bytes of |output| with random data.
+// Note: The random data is cryptographically secure, but use the RNG in crypto/
+// for security-sensitive purposes instead of this function.
 BASE_EXPORT void RandBytes(void* output, size_t output_length);
 
-// Fills a string of length |length| with with cryptographically strong random
-// data and returns it.  |length| should be nonzero.
+// Fills a string of length |length| with with random data and returns it.
+// |length| should be nonzero.
+//
+// Note: The random data is cryptographically secure, but use the RNG in crypto/
+// for security-sensitive purposes instead of this function.
 //
 // Note that this is a variation of |RandBytes| with a different return type.
 BASE_EXPORT std::string RandBytesAsString(size_t length);
 
 #ifdef OS_POSIX
 BASE_EXPORT int GetUrandomFD();
 #endif
 
 }  // namespace base
 
 #endif  // BASE_RAND_UTIL_H_