Want to have a password input screen just like the unlock the device interface

I'd like to design a password input screen and I'd like the "unlock device" interface. How to implement it in iphone SDK? Any sample code? I can't find the four square box that in IB. Shall I build it my own?开发者_开发知识库

KVPasscodeViewController (mine), is available here: https://github.com/Koolistov/Passcode (BSD license).