Software that can wipe out my iPhone data permanently?

I posted this question earlier. I just wanna make it clear though. I'm selling my iPhone 5s to buy a new phone. I have a lot of privacy information stored in my 5s and apparently, resetting it to factory settings and deleting all files are just not enough because it can be restored. I tried data recovery program, and I was surprised that it was able to restore all my files that I deleted. So I wanna know if there's any way that can wipe out all the files and make my iPhone data unrecoverable.

Look in the app store for 'free space wipe'

iShredder 3 is one that comes up in search's, but i've never used it.

an easier method is to set your camera to video, record at the highest resolution and just let it fill the memory, take hundreds of pictures of the floor, ceiling, walls etc and fill the memory.

this way you have wiped over any data that is recoverable, if someone tries to recover, all they will get is the video/pictures you just took to fill the memory.

You must know that you contacts and messages and some small icons are stored in your iphone sqlite database. And the others information are stored in your iphone or card. So you want to wipe data on you iphone. Below the two steps:
1. Clear your sqlite database with sqlite database tools.
2. Connect you iphone to PC and use winhex to set all the sectors to zero.
3. Use the data recovery software such as (togethershare data recovery software)to test the effects of wipe.
4. If not, please copy some other data to your iphone to cover or rewrite the original data.