I was mulling over some old emails about randomly-generated
numbers and realized that if I had an imperfectly random
source (something less than 100% unpredictable), that
compressing the output would compress it to the point where
it was nearly so. Would there be any reason to choose one
algorithm over another for this application?
I see where you're coming from, but take an imperfectly random source
and apply a deterministic function to it, and if I recall correctly, you
still have a imperfectly random output. It would be better to use
something like Von Neumann's unbiasing algorithm (or any of the newer
improvements) to strip out the non-randomness.
I recall talking to a CS prof once who said that LZW
compression was optimal, which seemed and still seems
really odd to me because optimal compression would generate a
null output file. So surely he meant asymptotically optimal,
or e-close to optimal, or something like that... anyone know?
He probably meant optimal in the information theoretic sense. If that
was the case, then no, optimal compression will not yield a null-length
output -- it will give you the minimum length output that could
represent your input from among all inputs. Or maybe he didn't ;)
Regards,
Jeremy Hansen, MS, CISSP
Director of Security
RAIR Technologies
Any views or opinions presented in this email are solely those of the
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RAIR Technologies * Brookfield, WI * 262-780-6000
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