[RC5] RC5-72, and Unicos?

Décio Luiz Gazzoni Filho decio at revistapcs.com.br
Fri Dec 27 21:57:04 EST 2002

Hash: SHA1

On Friday 27 December 2002 18:57, Ethan wrote:
> Hello.
>  I noticed there is now a new RSA challenge.
>  I own a 32 cpu Cray J932se system. Although I don't have the OS or
> compilers (yet), I was wondering if the vector processors would be good or
> bad at contributing to the project?

Probably good. They would surely need a core of their own (current cores only 
do 2-4 keys at a time while the vector length on these processors might be 
anywhere from 32-128.) I would happily do that if provided with some 
datasheets of the CPUs, a shell account on the machine and of course the 
development toolchain.

>  Unfortunately I don't know a great deal about the advantages of Vector
> CPUs, and if they would be good when applied towards something like the
> RC5 challenge.
>  Assuming I can afford to power the system (90 amps @ 220vac rated) and
> get the compilers and OS (Cray wants $20k, can I sweet talk them for
> non-commercial use?) I would love to get our team back together and push
> for the top.
>  The system was purchased used on the surplus market, and is privately
> owned.
>  Anyone familiar enough with the operations of cracking RSA, and Cray /
> Unicos and Vector CPUs to tell me if this machine would be useful and
> outperform a good number of P3 systems?

I can't comment without having system specs but I think it would be more power 
efficient to use commodity systems.

>  I do see some reference to people on a cypherpunks list talking about
> cracking 512bit RSA using Crays, but they weren't specific if it was a
> vector or MPU system. And of course, the programming plays a huge part in
> it. This particular application shouldn't require parallelization?

These references you have are for the RSA factoring challenges, and the 
cryptosystem in question is the RSA public key cryptosystem. What 
distributed.net is taking part now are the RSA Secret Key challenges, and the 
cypher is question is RC5, a symmetric key cypher. They are completely 
unrelated, except that they were invented by the same person (Ronald Rivest 
alone for RC5, and in cooperation with Adi Shamir and Leonard Adleman for the 
public-key cryptosystem.)

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