how to secure downloading mp3 or flv files in nginx

[XUFENG]

Hi all,

	Can nginx achieve this goal?

	On my php page,I give the url to my mp3 file in this format http://mp3.example.com/a.mp3?key=time()
then this request will go to nginx,can nginx do something like compare the uri /a.mp3?key=time() with the current time() and if it is 180 seconds ago,403 error will return or it will rewrite to the normal file /a.mp3
	
Thanks in advance.  				
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XUFENG
2009-06-15