public synchronized Player getPlayer(FreerailsPrincipal p) {
    NonNullElements i =
        new NonNullElements(KEY.PLAYERS, serverGameEngine.getWorld(), Player.AUTHORITATIVE);

    while (i.next()) {
      if (((Player) i.getElement()).getPrincipal().equals(p)) {
        return (Player) i.getElement();
      }
    }

    return null;
  }
  /**
   * TODO deprecate strings in favour of certificates XXX currently we only support a single player
   * per connection.
   *
   * @param player the player trying to connect
   * @return true if the connection was successfully identified with the specified player
   */
  public synchronized boolean addConnection(ConnectionToServer c, Player player, byte[] signature) {
    logger.log(Level.INFO, "Authenticating player " + player.getName());

    /* determine whether this identity already exists */
    NonNullElements i =
        new NonNullElements(KEY.PLAYERS, serverGameEngine.getWorld(), Player.AUTHORITATIVE);

    while (i.next()) {
      Player p = (Player) i.getElement();

      if (p.getName().equals(player.getName())) {
        /* this player already exists */
        /* is this identity already connected ? */
        if (principals.containsValue(p)) {
          logger.log(Level.INFO, "Player " + p.getName() + " is already" + " connected");

          return false;
        }

        /* is this player the same as the one which previously
         * connected under the same name? */
        logger.log(Level.FINE, "Verifying player " + p + " with " + player);

        if (!p.verify(player, signature)) {
          logger.log(Level.WARNING, "Couldn't verify signature of player " + p.getName());

          return false;
        }

        principals.put(c, p);

        /* set the connection world */
        if (c instanceof LocalConnection) {
          // don't create a WorldView, since the local client needs
          // to synchronize against the world object itself.
          c.setWorld(serverGameEngine.getWorld());
        } else {
          c.setWorld(new WorldView(serverGameEngine.getWorld(), p.getPrincipal()));
        }

        return true;
      }
    }

    /* this player does not already exist */
    logger.log(
        Level.INFO, "Adding player " + player.getName() + " to " + serverGameEngine.getWorld());

    MoveConfirmer mc =
        new MoveConfirmer(serverGameEngine.getMoveExecuter(), serverGameEngine.getMoveChainFork());
    AddPlayerMove m = new AddPlayerMove(serverGameEngine.getWorld(), player);
    MoveStatus ms = mc.confirmMove(m, null);

    assert ms == MoveStatus.MOVE_OK;

    /*
     * get the newly created player-with-principal
     */
    World w = serverGameEngine.getWorld();
    assert (w != null);
    player =
        (Player)
            w.get(KEY.PLAYERS, w.size(KEY.PLAYERS, Player.AUTHORITATIVE) - 1, Player.AUTHORITATIVE);

    principals.put(c, player);

    /* Perform any moves necessary for adding a new player */
    serverGameEngine
        .getMoveExecuter()
        .processMove(statGatherer.generateNewPlayerMove(player.getPrincipal()), c);
    serverGameEngine
        .getMoveExecuter()
        .processMove(scenario.getSetupMoves(serverGameEngine.getWorld(), player.getPrincipal()), c);

    /* set the connection world */
    c.setWorld(new WorldView(serverGameEngine.getWorld(), player.getPrincipal()));
    return true;
  }