[1] http://www.engadget.com/2014/03/05/how-to-set-up-a-complex-p...
Of course this isn't ever actually used - in practice users choose four to eight digit passcodes.
Users should, if they want to secure their information, use a randomly chosen passcode of approximately 30 digits long.
[1] http://www.engadget.com/2014/03/05/how-to-set-up-a-complex-p...