How to delete a file such that the delete is irreversable?

Question

I want to delete a sensitive file (using C++), in a way that the file will not be recoverable.

I was thinking of simply rewriting over the file and then delete it, Is it enough or do I have to perform more actions ?

Answer 1

Here is an interesting paper:

http://www.filesystems.org/docs/secdel/secdel.html

It adresses some issues with overwriting of files. Especially you can't be sure that the newly written data was written to the same location and that it's impossible to recover data that was overwritten just a very few times or even once (on modern media).