The Flash security sandbox does not allow you to access the
local files sytems except for uploading files through user input.
So, if your smart card is part of your local files system via
mounting etc, you can only acess the data via the file upload
There are however some ways to do this with a little work. I
have seen one example which uses the Flex - Ajax bridge and an
applet. If you are interested, check out Kevin Hoyt's flex file