@Test
  public void testComputeSharedSecretWithRfcIteration() throws Exception {
    byte[] k = new byte[32];
    k[0] = 9;
    byte[] prevK = k;
    k = X25519.computeSharedSecret(k, prevK);
    assertEquals("422c8e7a6227d7bca1350b3e2bb7279f7897b87bb6854b783c60e80311ae3079", Hex.encode(k));
    for (int i = 0; i < 999; i++) {
      byte[] tmp = k;
      k = X25519.computeSharedSecret(k, prevK);
      prevK = tmp;
    }
    assertEquals("684cf59ba83309552800ef566f2f4d3c1c3887c49360e3875f2eb94d99532c51", Hex.encode(k));
    // Omitting 1M iteration to limit the test runtime.
  }
Iteration test in Section 5.2 of RFC 7748. https://tools.ietf.org/html/rfc7748
java_src/src/test/java/com/google/crypto/tink/subtle/X25519Test.java