[104866] in Cypherpunks
Re: Shuffling
daemon@ATHENA.MIT.EDU (Alex Alten)
Fri Oct 30 02:25:31 1998
Date: Thu, 29 Oct 1998 22:14:01 -0800
To: Mok-Kong Shen <mok-kong.shen@stud.uni-muenchen.de>, coderpunks@toad.com
From: Alex Alten <Alten@home.com>
In-Reply-To: <3638203B.4FB0A089@stud.uni-muenchen.de>
Reply-To: Alex Alten <Alten@home.com>
At 08:58 AM 10/29/98 +0100, Mok-Kong Shen wrote:
>Alex Alten wrote:
>
>> The concept of swapping to get a random string of bits is very interesting.
>> >From what I understand when one shuffles a deck of 52 cards 7 or more
times
>> the card order becomes unpredictable e.g. random. The shuffle must be
>> what is called a "near perfect" shuffle. In other words the cards can't
>
>You are right. The quality of shuffling depends on the quality of
>the PRNG being used in the shuffling algorithm.
>
Taking this a step further. Say you had a security system where all messages
were exactly some fixed number of bytes, say 64 bytes each. Now the number
of possible combinations is 64!, which is somewhere around 2^296. This means
that if you could represent each unique shuffle pattern with a unique number
you would have a cryptosystem with keys of 296 bits each. However if the
messages are structured or subject to frequency analysis then I suspect that
the strength would be reduced quite a bit. In that case it's probably better
to use it to construct a message length random key to XOR against the clear
text. One could build practical variants that could be useful in such
a restricted message size environment (say a payment system with small
monetary messages).
Anyway it's a fun mental doodle if nothing else. Good night!
- Alex
--
Alex Alten
Alten@Home.Com
Alten@TriStrata.Com
P.O. Box 11406
Pleasanton, CA 94588 USA
(925) 417-0159
