[rc5] Re: One Time Pad

Richard Freeman rfreeman at netaxs.com
Tue Oct 28 16:45:01 EST 1997


On Mon, 27 Oct 1997, Paul Leskinen wrote:

> 
> Now, I've thought of a good approximation to a true OTP system:  Use an
> arbitrarily long key (however many bits you want), and use that to
> generate a unique irrational number, the digits of which become your
> random key stream. That would be a virutually unbreakable system
> (statistical methods would not work), with a suitably long key. I really
> don't know if it's even feasible, but hey, it's just a thought. 
> 

It may be feasible - but I am not convinced that the stream of numbers
from an irrational number is truly random.  Sure - it may look random -
but it is based on a simple mathematical expression.  Can you prove that
when the Russian mathematicians crack the number theory of irrational
numbers (and their govt of course keeps it hushed up) that they won't be
able to mount an attack using this knowledge.  The true OTP is
mathematically secore.  Your approximation is probably very good - but I
wouldn't put it on the same level without a true proof.  Your initial key
for example need not be as long as the message - that makes for a finite
number of possible keys - and possibly only a few of them will lead to
streams that decipher to plain english...  With the OTP any arbitrary
message can be arrived at by chosing the appropriate key (making it
impossible to tell which is the right key).

Just a couple of scattered thoughts...

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Richard T. Freeman <rfreeman at netaxs.com> - finger for pgp key
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