How can i Permanently Delete private " pictures on my Sony Camera Memory Stick?

I have private pictures on my sony digital camera's memory stick and i want to know how to permanently delete those pictures since i have heard that there are ways to bring back deleted files. I've tried reformatting the Memory Stick but it won't let me Reformat it, What should i do? Those are pictures that i don't want to be leaked out.|||formatting the card make it impossible to recovery them using any image rescue software, if you are unable to do it on camera try connecting to the computer via the memory card reader and format from there, be sure to format the card again on camera before use to ensure that there will be no problems with your camera compatibility.