code: public static void changePassphrase(Path pathToVault, String masterkeyFilename, CharSequence oldPassphrase, CharSequence newPassphrase)
  			throws InvalidPassphraseException, FileSystemNeedsMigrationException, IOException {
  		changePassphrase(pathToVault, masterkeyFilename, new byte[0], oldPassphrase, newPassphrase);
  	}
docs: Changes the passphrase of a vault at the given path.
  
  @param pathToVault Vault directory
  @param masterkeyFilename Name of the masterkey file
  @param oldPassphrase Current passphrase
  @param newPassphrase Future passphrase
  @throws InvalidPassphraseException If <code>oldPassphrase</code> can not be used to unlock the vault.
  @throws FileSystemNeedsMigrationException if the vault format needs to get updated.
  @throws IOException If the masterkey could not be read or written.
  @see #changePassphrase(Path, String, byte[], CharSequence, CharSequence)
  @since 1.1.0