the iPhone uses 256 bit encryption. every iPhone since the a4 system on a chip has had this feature.
the iPhone is secure as long as you don't write the key down.
when people say "30 characters should be enough !" on your wifi network, that is what your iPhone is dong automatically.
dvd uses 40 bit keys and blu ray uses 128 bit keys. they would of had a hard time ripping star wars and terminator , if the keys weren't discovered, and given away
don't write it down means don't jail break your device. if you jailbreak your device , it might backup your key somewhere.
if you had a computer and it made 1 trillion guesses per second to try and get back the data you wiped, it would take :
3.53 hundred million centuries
here is a good reddit post
http://www.reddit.com/r/theydidthem...e_and_energy_required_to_bruteforce_a_aes256/
a lot of crypto people say that AES-256 is so secure, that even the quantum computers in the future can't brute force your iPhone. (meaning the iPhone can't be recovered in the average human beings lifetime or the lifetime of the known universe)
they can go after itunes backups and iCloud. but the iPhone, i doubt it