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Magnetic Force Microscopy?

Discussion in 'Electronic Design' started by Adam Aglionby, Nov 17, 2003.

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  1. Someone who can make MFM is probably able to make much more money with
    normal design work in stead of criminal activity.

    So that leaves only people who have access to MFM technology.

    anyway, you don't even need special software, on a unix system just "dd
    if=/dev/random of=/dev/somedisk" will do the job.

    cheers,
    Jeroen.
     
  2. Mike

    Mike Guest

    I dunno about the MFM machine, but the usenix paper is from 1996, and
    references technology that was already several years old.

    If we look at an average modern drive (a Maxtor 20.4GB DiamondMax), it has
    a track density of 17,305 per inch, and a flux density of 236 to 306 flux
    changes per inch. When that Usenix paper was written, both those numbers
    were lower by around an order of magnitude. That means that today's data
    bit is stored in roughly 1/100 the area that it was ten years ago.

    With the advent of communication channel techniques (PRML codes and Viterbi
    detectors) applied to the disk channel, data bits no longer needed to be
    isolated from adjacent bits in the same track (adjacent tracks are another
    matter). In addition, the raw error rate coming from the read channel is
    now around 10^-4, with the ECC improving the final error rate to less than
    10^-12; prior to the communication channel era the raw error rate was
    generally 10^-12. The reduction in raw error rate means that the SNR on the
    disk is much much lower than it was in the old days.

    The net result is that there is far less signal there to recover even
    before the previous data has been overwritten, much less after it's been
    overwritten more than a couple times.

    -- Mike --
     
  3. Uns Lider

    Uns Lider Guest

    Several individuals have made working homemade scanning tunneling
    microscopes:

    http://www.e-basteln.de/references.htm

    I don't think it'd be too much harder to make an MFM?

    -- uns
     
  4. 250GB drives are pretty cheap today. Not only would that be a seriously
    bad S/N ratio for old data, but it could take a very long time to find
    what you're looking for with a tiny scanner.
     
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