crypto: remove slight bias in key generation due to modulo

2 files changed, 48 insertions, 0 deletions

diff --git a/tests/unit_tests/CMakeLists.txt b/tests/unit_tests/CMakeLists.txt
index 6d79ba74b..06112d3ee 100644
--- a/tests/unit_tests/CMakeLists.txt
+++ b/tests/unit_tests/CMakeLists.txt
@@ -55,6 +55,7 @@ set(unit_tests_sources
   mul_div.cpp
   multisig.cpp
   parse_amount.cpp
+  random.cpp
   serialization.cpp
   sha256.cpp
   slow_memmem.cpp
diff --git a/tests/unit_tests/random.cpp b/tests/unit_tests/random.cpp
new file mode 100644
index 000000000..7653453cd
--- /dev/null
+++ b/tests/unit_tests/random.cpp
@@ -0,0 +1,47 @@
+// Copyright (c) 2018, The Monero Project
+// 
+// All rights reserved.
+// 
+// Redistribution and use in source and binary forms, with or without modification, are
+// permitted provided that the following conditions are met:
+// 
+// 1. Redistributions of source code must retain the above copyright notice, this list of
+//    conditions and the following disclaimer.
+// 
+// 2. Redistributions in binary form must reproduce the above copyright notice, this list
+//    of conditions and the following disclaimer in the documentation and/or other
+//    materials provided with the distribution.
+// 
+// 3. Neither the name of the copyright holder nor the names of its contributors may be
+//    used to endorse or promote products derived from this software without specific
+//    prior written permission.
+// 
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
+// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "gtest/gtest.h"
+
+#include "crypto/crypto.h"
+
+extern "C" {
+#include "crypto/crypto-ops.h"
+}
+
+TEST(random32_unbiased, less_than_order)
+{
+  unsigned char tmp[32], tmp2[32];
+  for (int i = 0; i < 1000; ++i)
+  {
+    crypto::random32_unbiased(tmp);
+    memcpy(tmp2, tmp, 32);
+    sc_reduce32(tmp2);
+    ASSERT_EQ(memcmp(tmp, tmp2, 32), 0);
+  }
+}