How can I make another button highlighten on popup window on Mac by using Keyboard

Go to Preferences -> Keyboard. At the bottom, turn on "All controls" under "Full Keyboard Access".

The alternate option will be highlighted with a blue ring. Hitting space will activate this. If there are multiple options, hitting tab will alternate between them.

For English/Mac OSX 10.10:

Go to Keyboard in System Preferences, and then select 'All controls'. Space will select the alternate option if two options. If more than two options then tab will alternate between them.

PS: I would much rather the option of using arrow keys and enter. Interested to know if anyone knows how to hack this?

After reading Tricon's answer, I got the way!!!

Just see the following shortcuts.

Preferences -> Keyboard -> Keyboard & keyboard input (I don't know the correct English menu, I'm using Korean "탭이 초점을 이동하는 방식 변경 (^F7) )

Once you do ^F7 (In case of mac book, Control + fn + F7) on a popup window, you can travel over buttons on any popup windw!!!

Thank you Tricon for giving me clue :)