posted 03 September 2003 14:06            

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OK, its non Kyma topic.

Erased data can be extrapolated from residual magnetic patterns?

I wonder if that could be applied to analogue recordings on tape.
http://developer.apple.com/qa/fl/fl11.html

"......The other thing you need to consider is that simply writing an alternating pattern of zeros and ones to a disk is no longer sufficient to "securely erase" a drive. The recent research on the behavior of erase bands of magnetic media recording and the availability of magnetic force microscopy for the analysis of magnetic media suggests the feasibility of a recovery attack on erased data. Further, it has been suggested that the media sanitization guidelines might also be inadequate for the magnetic encoding scheme used by modern disk drives. Knowing what pattern to write is a science in itself........"

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posted 06 September 2003 11:48            

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Indeed... people I once worked for did this sort of thing all the time...

[I understood, at the time, that their recovery process was good to about 6 or 7 layers deep, of over-recordings.

About the only way to assure complete removal of information from magnetic media is by way of something called the Curie Effect, where the magnetic media are heated above a critical temperature, called the Curie Temperature, of the material. Only then does magnetization completely cease so that upon cooling, the original magnetization patterns are erased. This might be possible with laser spot heating of the material during the recording process.]

- DM

[This message has been edited by David McClain (edited 06 September 2003).]

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