Hi folks, I'm planning to sell my iPhone 3GS (US, locked to AT&T, firmware 3.1.3) on eBay. First thing I need to do is to delete all my data from it. Last time, when I was running jailbroken 3.1.2 I did go to Settings->General->Reset->Erase all Content and Settings, and it really messed up my phone. Had to restore to 3.1.3 due to that. I need the phone to stay at 3.1.3, so how do I make sure that all my data is deleted from the iPhone safely so that I don't have to do restore again. I am afraid Apple auth servers will not sign old 3.1.3 firmware and force me to upgrade to 4.0. Thanks.