The authority has the power to invest any funds held in reserve, sinking funds, capital reserve funds, or any funds not required for immediate disbursement in property or in securities in which the state treasurer may legally invest funds subject to his control; and to sell from time to time such securities thus purchased and held; and to deposit any securities in any trust bank within or without the state. In addition, the authority has the power to invest any such funds in unsecured promissory notes of a national bank having the highest investment ratings. Any funds deposited in a banking institution shall be secured in such manner and subject to such terms and conditions as the board may determine, with or without payment of any interest on such deposit, including, without limitation, time deposits evidenced by certificates of deposit. Any commercial bank incorporated under the laws of this state which may act as a depository of any funds of the authority may issue indemnifying bonds or may pledge such securities as may be required by the board.