[rc5] Re: One Time Pad
pcr at ic.net
Mon Oct 27 19:35:51 EST 1997
>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.
You've just described a stream cypher. The problem is that the
irrational number isn't really random. In fact, it's 100% predictable.
The art of developing stream cyphers is deep and complex. It's
VERY HARD to create a stream cypher that doesn't have some
pattern to it to the "random" component.
Look at "Applied Cryptography" (2nd Ed), section 9.4 (starts on
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