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Re: Gao's Chaos Cryptosystem



>At 12:37 AM 9/6/97 PDT, Nobuki Nakatuji wrote:
>>GCC(Gao's Chaos Cryptosystem)
>>GCC uses the newest chaos logic and is conventional cryptosystem 
>>stream cipher encryption. It is high speed and allows variable-length 
keys,
>>making it very reliable and suitable for use in multimedia.
>>http://www.iisi.co.jp/reserch/GCC-over.htm
>>[Products using it, user-friendliness, etc.]
>
>Good user interfaces and high speed are important, but not enough.
>How strong is the cypher?  Where is the academic research behind it?
>What is the algorithm?  Why should we trust it?  Who else has tested 
it?
>Other people have built cyphers based on chaotic systems, and found
>they were weak when analyzed properly.  Building good cryptosystems is
>difficult.
>
>The web page doesn't give any details about the algorithm,
>except saying that it uses chaos and strange attractors,
>uses variable-length keys, and has a structure that uses
>XOR of the stream cypher with the plaintext.
>It does say the algorithm has a 0-1 balance of 0.5/0.5 
>(which any good cryptosystems do) and has a medium-sized state space 
(2**96).
>
>It claims that because it's a one-way stream cypher, that makes it
>safe against chosen plaintext attacks.  That's not true.
>Choose a plaintext of all zeros, and that gives you the
>output of the chaotic system which you can analyze for patterns.
>If you know the structure of the chaotic system, you can
>analyze the mathematics to see how to find the state space,
>and how to find the future output from the current output and
>the state space - if the algorithm is strong, this is difficult,
>but if the algorithm is weak, this is easy.  If you don't publish
>the algorithm, nobody can prove that it's strong, and in the
>world of cryptosystems, that means nobody will trust it,
>because we know how weak many other strong-looking algorithms are.
>
>
>
Please see http://arrirs02.uta.edu/ccc/upcoming.html.
and,I have thesis of this algorithm write in Japanese language.



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