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Wiping an SD card to NASA standards

Discussion in 'Computer Related Help & Discussion' started by Max resist, Sep 7, 2018.

  1. Max resist

    Max resist Well-Known Member

    6 times overwrite.
    = US Military standards
    well nigh impossible to recover anything.
    s true......
    SD cards are not hard drives.
    That's if your James Bond LOL
     
  2. Benchista

    Benchista Which Tyler

    I thought your method was superior - just shove it in your Nikon. ;)
     
    DaveM399 and dream_police like this.
  3. Roger Hicks

    Roger Hicks Well-Known Member

    Dear Nick,

    Until it breaks?

    Cheers,

    R.
     
  4. Benchista

    Benchista Which Tyler

    Seems to be the method, yes, Roger.
     
  5. GeoffR

    GeoffR Well-Known Member

    Pretty difficult to retrieve data from a broken SD card. NASA standard is to send it into the sun.
     
  6. Max resist

    Max resist Well-Known Member

    The bits might be able to be sellotaped back together.?
    All the Kings Horses and All the Kings men......
    But seriously just HOW does an SD card erase single images and WHERE do they vanish to?
     
  7. Benchista

    Benchista Which Tyler

    Answered in your other thread.
     
  8. RogerMac

    RogerMac Well-Known Member

    They do not vanish the data remains there but the allocation table (which gives the address of the actual image) is overwritten and marked as "available"
    I think that Norton utilities provide a utility to overwrite and completely erase unused space on the disc. Incidentally I was once told that discs held in battlefield situations were all removable and a bath of nitric acid was adjacent - so that if the Russians came through
    the whole structure of the disc could be destroyed, I don't know if that still applies but if I scrap a computer I always put a chisel through the hard disc first
     
  9. PeteRob

    PeteRob Well-Known Member

    Assuming you really don't know.

    There are two aspects to storing electronic information - the information itself and the location in which it is stored. When you delete a file (any type of electronic file) the first thing that happens is the location information is marked free for re-use. The information itself remains. With recovery tools you can "undelete". In the normal due course the storage will eventually be re-used, although in modern PC computer systems this is prevented until you empty the trash-can which is a safety step introduced to prevent accidental deletes. If you want to deliberately remove the information then you have to overwrite it with something else. For SD card formatting some cameras offer high and low level formats. A high level format removes only the location information. A low level format overwrites all the information on the card and (I assume) checks the card integrity.
     
  10. Max resist

    Max resist Well-Known Member

    Hmm all makes sense.
    So If you want to delete confidential photographic data-bank statements etc made for purposes of sending to Bank Customer service-
    you would need to over write the entire SD card used -unless the deleted images were the first ones in sequence when a renewed
    overwrite would deal with them'first'?
    I wonder what effect running a magnet over the card would have?
    (Cassette tapes can be erased in this manner apparently)
    If your SD card has the capacity to store say 500 images then it would be necessary to make
    500 new images to completely over write the said card.
    This would obviously be tedious and take a long time.
    Is there no 'quick'way to do it?
    Does formatting the card in the camera do it?
     
  11. PeteRob

    PeteRob Well-Known Member

    Memory cards are not magnetic. You need to give it a low-level format. If you do this in a computer then reformat it in the camera before use because in-camera formatting doesn't just format it also adds a standard file structure needed for correct camera operation.

    Adding images doesn't work. You have no control over where the information is written and (unless I am mixing up SD and CD cards) the memory card use is optimised so that all parts of the storage are equally used over time. It doesn't "fill-up from the beginning" every time you save the first file after a format.
     
  12. GeoffR

    GeoffR Well-Known Member

    If you really want to remove all the data from a card you need a utility on your computer designed specifically for the purpose. The process is slow and works by overwriting the data several times then removing the residual data to leave, essentially, a blank card.
     
  13. EightBitTony

    EightBitTony Well-Known Member

    Don't forget either that flash (SD card, SSD, USB, etc.) memory controllers all lie to the computer about what sector you're writing to, in order to balance writes across the entire device, to ensure longevity. So any algorithm designed to 'write over every sector with 0's' may well have no effect on an SD card, or may not have the desired effect.
     
  14. GeoffR

    GeoffR Well-Known Member

    The only reliable way is to fill the card with images, "erase" and repeat the process five times or so. Very time consuming. Given the low cost of SD cards much quicker and cheaper to stick the card through a shredder, mine does a good job with credit cards.
     
    RogerMac likes this.
  15. Benchista

    Benchista Which Tyler

    I wonder why someone with the username of an extreme right wing white power punk group is so obsessed with destroying data...
     
  16. PeteRob

    PeteRob Well-Known Member

    I'd assumed an etching enthusiast.
     
  17. GeoffR

    GeoffR Well-Known Member

    For all we know he is into making his own Printed Circuit Boards
     
  18. PeteRob

    PeteRob Well-Known Member

    It was PCB manufacture I was thinking of when I saw the term resist. I think it was actually called photo-resist. I'll have to ask my wife as it was she that worked on it circa 1971-2. Seems a long time ago.
     
  19. Andrew Flannigan

    Andrew Flannigan Well-Known Member

  20. GeoffR

    GeoffR Well-Known Member

    Depends how it is applied, for prototyping you can/could get resist pens that allowed the circuit to be drawn by hand.
     

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