Well, it's remarkably easy to create a "secure erase" utility:
1: create a 512K file with all zeros or random noise.
2: write a script that iterates three times through
- delete all files on a volume
- write successive copies of the reference file, appending something to
the file name each time, until the volume is full.
3: add a closure to delete all files on the volume one final time.
I just created a utility like this in 4 minutes with AppleScript on Mac OS X and checked it with a data recovery utility. All I get from the data recovery effort is random noise back from the last iteration of the write loop. It's pretty efficient, takes only about thirty seconds to run on a 1G card.
Godfrey
On May 19, 2005, at 10:32 AM, P. J. Alling wrote:
I understand the issues with CF card longevity. A secure erase say once a week is unlikely to noticeably effect the life of my cards anyway. I'm more likely to lose them before they wear out in any case. I'd rather find a utility someone else has written to do a secure erase than write one myself. Shareware is good, Freeware is better. So far the only place I've been able to find this is Kodak for the 14n/c it seems.
Godfrey DiGiorgi wrote:
On May 19, 2005, at 9:33 AM, P. J. Alling wrote:
Ok, so you've got your CF card, you copy the images from the card to you hard drive and create a CD/DVD/whatever backup. Delete all the files on the card and the data is still the still recoverable. Suppose you want to clean the card completely. I haven't been able to find a utility to do that. Even a "full format" in DOS seems to just do a fast format, (rewrite the FAT table). Has anyone found such a beast or will I have to write one myself?
Yes it is a paranoid question, on the other hand these are paranoid times, and so few people seem to realize that.
A "secure erase" command generally is implemented to do a write of "0" (or random) value to every location on the volume at least three times.
Most implementations of the format command for flash media just rewrite the file directory information and map bad blocks to maximize the lifespan of the media. Flash media has a limit to the maximum number of writes that can be performed reliably, the implementors want to minimize unnecessary writes.
Godfrey
-- A man's only as old as the woman he feels. --Groucho Marx
