Removing some files from history

Hello all
I'm not yet subscribed, but I wish I shall get reply anyway

I'm going to make my repository public, but I have found that one of
my files contains some private data that I would not like to share.
Is it possible to remove that file from all commits in my local
repository history before publishing it?
Or it would be easier to start publishing with just my current state
(whith all private data cleaned up)?

Thanks in advance.
Gennady