java/src/test/java/com/google/crypto/tink/subtle/Ed25519Test.java

// Copyright 2017 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
////////////////////////////////////////////////////////////////////////////////

package com.google.crypto.tink.subtle;

import static org.junit.Assert.assertArrayEquals;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;

import java.util.Arrays;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.JUnit4;

/** Unit tests for Ed25519. */
@RunWith(JUnit4.class)
public class Ed25519Test {
  @Test
  public void testGroupOrder() throws Exception {
    assertEquals(32, Ed25519.GROUP_ORDER.length);
    byte[] result = Ed25519.scalarMultWithBaseToBytes(Ed25519.GROUP_ORDER);
    assertEquals(1, result[0]);
    for (int i = 1; i < 32; i++) {
      assertEquals(0, result[i]);
    }
  }

  /** Test whether sign/verify method accidentally changes the public key or hashedPrivateKey. */
  @Test
  public void testUnmodifiedKey() throws Exception {
    byte[] privateKey = Random.randBytes(Field25519.FIELD_LEN);
    byte[] hashedPrivateKey = Ed25519.getHashedScalar(privateKey);
    byte[] originalHashedPrivateKey =
        Arrays.copyOfRange(hashedPrivateKey, 0, hashedPrivateKey.length);
    byte[] publicKey = Ed25519.scalarMultWithBaseToBytes(hashedPrivateKey);
    byte[] originalPublicKey = Arrays.copyOfRange(publicKey, 0, publicKey.length);
    for (int i = 0; i < 64; i++) {
      byte[] msg = Random.randBytes(1024);
      byte[] sig = Ed25519.sign(msg, publicKey, hashedPrivateKey);
      assertTrue(Ed25519.verify(msg, sig, publicKey));
      assertArrayEquals(originalHashedPrivateKey, hashedPrivateKey);
      assertArrayEquals(originalPublicKey, publicKey);
    }
  }
}