byte[] key = "Jefe".getBytes(UTF_8);
    String data = "what do ya want for nothing?";

    checkMd5("750c783e6ab0b503eaa86e310a5db738", key, data);
  }

  public void testRfc2202_hmacMd5_case3() {
    byte[] key = fillByteArray(16, 0xaa);
    byte[] data = fillByteArray(50, 0xdd);

    checkMd5("56be34521d144c88dbb8c733f0e8b3f6", key, data);
  }

  public void testRfc2202_hmacMd5_case4() {