crypto/curve25519_unittest.cc

// Copyright (c) 2013 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.

#include "crypto/curve25519.h"

#include <stdint.h>

#include <string>

#include "crypto/random.h"
#include "testing/gtest/include/gtest/gtest.h"

namespace crypto {

// Test that the basic shared key exchange identity holds: that both parties end
// up with the same shared key. This test starts with a fixed private key for
// two parties: alice and bob. Runs ScalarBaseMult and ScalarMult to compute
// public key and shared key for alice and bob. It asserts that alice and bob
// have the same shared key.
TEST(Curve25519, SharedKeyIdentity) {
  uint8_t alice_private_key[curve25519::kScalarBytes] = {3};
  uint8_t bob_private_key[curve25519::kScalarBytes] = {5};

  // Get public key for alice and bob.
  uint8_t alice_public_key[curve25519::kBytes];
  curve25519::ScalarBaseMult(alice_private_key, alice_public_key);

  uint8_t bob_public_key[curve25519::kBytes];
  curve25519::ScalarBaseMult(bob_private_key, bob_public_key);

  // Get the shared key for alice, by using alice's private key and bob's
  // public key.
  uint8_t alice_shared_key[curve25519::kBytes];
  curve25519::ScalarMult(alice_private_key, bob_public_key, alice_shared_key);

  // Get the shared key for bob, by using bob's private key and alice's public
  // key.
  uint8_t bob_shared_key[curve25519::kBytes];
  curve25519::ScalarMult(bob_private_key, alice_public_key, bob_shared_key);

  // Computed shared key of alice and bob should be the same.
  ASSERT_EQ(0, memcmp(alice_shared_key, bob_shared_key, curve25519::kBytes));
}

TEST(Curve25519, SmallOrder) {
  static const uint8_t kSmallOrderPoint[32] = {
      0xe0, 0xeb, 0x7a, 0x7c, 0x3b, 0x41, 0xb8, 0xae, 0x16, 0x56, 0xe3,
      0xfa, 0xf1, 0x9f, 0xc4, 0x6a, 0xda, 0x09, 0x8d, 0xeb, 0x9c, 0x32,
      0xb1, 0xfd, 0x86, 0x62, 0x05, 0x16, 0x5f, 0x49, 0xb8,
  };

  uint8_t out[32], private_key[32];
  memset(private_key, 0x11, sizeof(private_key));

  EXPECT_FALSE(curve25519::ScalarMult(private_key, kSmallOrderPoint, out));
}

}  // namespace crypto