began my presentation by discussing the illusory nature of deletion, whose objective of total erasure could never be accomplished. The crowd understood this instantly. I went on to explain that, at best, the data they wanted no one to see couldn’t be unwritten so much as overwritten: scribbled over, in a sense, with random or pseudo-random data until the original was rendered unreadable. But, I cautioned, even this approach had its drawbacks. There was always a chance that their operating system had silently hidden away a copy of the file they were hoping to delete in some temporary storage
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