From Jonathan Zdziarski:
iErase: Government Edition is the military-grade edition of iErase. For mission critical needs, iErase: Government Edition wipes the free space on your iPhone, iPad, or iPod Touch device using a three-pass approach: once, using an alternating 10101010 bit pattern, a second pass reversing the pattern, and a third pass randomizing the pattern. This approach is used by many governments for the wiping of classified data and other sensitive information.NOTE: Because this edition performs three passes, it takes three times longer than the consumer version of iErase.This helpful utility can be run periodically to effortlessly clear out old data and ensure it is beyond recovery. Because it doesn't erase your content or settings, you won't spend extra time restoring everything back onto your device, and the operation itself can take up less time than a full erase because it only operates on free space. Let it run while connected to a power source. Actual erase time varies depending on the amount of free space on the device. If you receive a phone call while iErase is running, it will pause and simply continue when you're finished.