Subject: Re: 1024 bit key considered insecure (sshd)
To: Dave Feustel <dfeustel@mindspring.com>
From: Perry E. Metzger <perry@piermont.com>
List: tech-security
Date: 08/29/2002 15:27:07
"Dave Feustel" <dfeustel@mindspring.com> writes:
> See _Cracking DES_

Wow. I'd never heard of that book before. I wonder why no one
mentioned brute force attacks on DES to me. It might have been
interesting to mention to my students in my annual graduate course in
cryptography.

>  (http://www.amazon.com/exec/obidos/tg/detail/-/1565925203/qid=1030639763/sr=1-1/ref=sr_1_1/102-5391104-6813765?v=glance&s=books
> 
> for a (by now obsolete) low-cost home-brew system
> for cracking DES. The available FPGA hardware has advanced
> considerably since this book was written.

Don't try teaching grandpa to suck eggs.

For extra credit, present the difference in computational complexity
between cracking a 56 bit DES key and factoring a 1024 bit
integer. And no, the difference is not a factor of 2^968. You should
especially go to the back of the room if you thought it was a straight
factor of 968, and if you thought it was a factor of 18 because 1024
is about 18 times larger than 56 you should confine your future job
searches to the food service and waste disposal industries.

For extra extra credit, figure out how many Virtex II FPGAs you would
need to try out Dan's new number field sieve trick with a 1024 bit key
if you want a result in one year. The Virtex II is ideal because of
its size and the presence of several IBM PPC cores on board. Hint: it
is not clear Xilinx can produce that many Virtex IIs for you at the
moment, though I'm sure they could scale up production for it.

-- 
Perry E. Metzger		perry@piermont.com
--
"Ask not what your country can force other people to do for you..."