6 Dec
2004
6 Dec
'04
16:11
Jeffrey L. Taylor wrote:
This isn't sufficient for a sufficiently determined and resourceful adversary. E.g. the intelligence services of major countries and corporations.
Magnetic disks are analog, not digital. E.g., setting a bit to 1 then 0 results in a slightly different magnetization levels and spatial patterns than setting it to 0 twice.
However, each time you overwrite, the orginal data gets pushed further down into the noise, making it more difficult to read. Eventually, a point will be reached, when it's impossible to tell the original data, from the noise. There is IIRC, a specified number of overwrites, with different patterns, so that the disk is considered fully erased.