Destroying Data

Harry Bartholomew bart at
Sun Dec 20 09:53:45 PST 1992

	In audio recording which uses magnetic media similar to disks
	the only way to thoroughly erase a tape is with a so-called
	bulk eraser. This applies a very strong a.c. magnetic field
	and then is gradually withdrawn from the tape to allow the 
	residual magnetism to "follow the hysteresis curve" down to 
	zero. This would be difficult to apply to disks except floppies.

	Consider also the technique used in the Norton Utilities
	program "Diskwipe" which takes a /g switch which "Follows
	certain government rules for wiping". I can't find the manual
	but I think it specifies how many repetitions are used and
	different values to write in each. 

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