How do a secure erase of an iPhone or iPad

Question

I want to sell an iPhone, but want to do a secure erase before handing it to someone else. By secure I meaning 35x rewriting its HD with random data.
How can one do this?
TIA,
Bill

Answer 1

I'm no expert on data detruction or data recovery; however, I am a physician who fears the 1.5 million dollar fine the US government can levy against me if patient data is exploited from a lost or stolen iPhone (which would violate HIPAA - even if I was prudent in attempting to secure that data.)  That said, I've tried to read and understand as much as possible from the experts in the fields of encryption (such as Phil ZImmerman of PGP fame back when I was a teenager) and the field of data destruction (such as Peter Gutmann, the creator of the legendary "35 pass Gutmann Wipe").  Two of Mr. Gutmann's most informative papers on the subject are "Secure Deletion of Data from Magnetic and Solid-State Memory" http://www.cs.auckland.ac.nz/~pgut001/pubs/secure_del.html and "Data Remanence in Semiconductor Devices" http://www.cypherpunks.to/~peter/usenix01.pdf Basically, he points out that the Gutmann 35-Pass wipe applies to old technology & though it is often referred to as "the MOST secure method of data deletion" - it simply does not apply to modern stoarge devices, including the iPhone's SDRAM, and using that technique is a complete waste of time.  He writes, "To erase SSDs.... Well, you're on your own there."  However, he points out as do several other replies to your question - that, because the data is initially stored using AES-256 encryption, using the iPhone's built in "Erase and Reset" function makes data recover NEARLY impossible.  If the people trying to get your data have access to some very sophisticated techniques and can get past the Flash Translation Layer - well, you have bigger worries & you should obliterate your phone.