[Cryptography] NIST Workshop on Elliptic Curve Cryptography Standards

[Ray Dillinger]

On 05/21/2015 01:25 PM, Arnold Reinhold wrote:
> True story: A friend of mine was working on having PCs communicate across air gaps using ultrasound. He was testing out his implementation of the concept when his kids came home and said “Dad, that’s really loud.” Lends a whole new purpose to take your kids to work day.
> 

Well-known fact to pediatricians and family-practice doctors,
but relatively unknown to the general public.  Adults hear up to
about 20 KHz.  More if they've avoided loud noises a lot during
their lives, less if they've regularly attended rock concerts or
used loud machinery at their primary job for any length of time.
But kids have both less accumulated inner ear damage, and
smaller ears.  They can often hear sounds in the 30 KHz range.

Any engineer attempting to design an ultrasound device should
keep this in mind.

Sometimes this has security implications:  I can think of two cases
that have already happened and one that came intriguingly close and
may have been developed more since.

  A few years past there was a ringtone that became popular
amongst the younger set because it was audible to them but not
to most adults.  They called it "Mosquito" as I recall.  And
sometimes used it in very minor security breaches like sending
signals each other covertly in the presence of adults who
attempted to forbid that sort of thing.

In another case, some asshole, not too long before that time,
had come up with a "child repeller" he tried to market, which
worked specifically by making loud annoying noises that most
grownups can't hear.  Fortunately for all concerned, his
business venture failed miserably when it turned out that
roughly 10% of grownups (who had mostly avoided rock concerts
and loud machinery) absolutely hated the loud annoying noises
too, and were repelled from businesses that had tried to
attract people by being free of annoying children.

And I recall at least one science project was undertaken by
a 13-year-old at the local junior high.  He was attempting
to electronically transpose voices up by six octaves where
grownups couldn't hear them.  But when the account I read was
written, he had a device that youngsters could hear, and
identify as speech, but could not understand.

				Bear




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