Re: Why crack more than 40bit RC5 keys? (WAS RE: RC5, hiding source code)

C Matthew Curtin (
Sun, 11 May 1997 21:10:58 -0400 (EDT)

>>>>> "Nelson" == Nelson Minar <> writes:

Nelson> I'm very excited about the potential uses of spare cycles,
Nelson> too.

I think we all are. Rocke articulated some of the excitement
surrounding the possibilities here very well last week, or the week
before. Making supercomputing available to anyone who can demonstrate
a need for that kind of power, without costing anyone anything is
indeed exciting stuff.

Nelson> Isn't
Nelson> anyone else worried that the news story is going to read "DES
Nelson> Secure - takes 10,000 computers six months to break one key"

No. The reason is because what we are doing is breaking DES keys in a
"reasonable" amount of time COMPLETELY WITHOUT COST. Except for the
time spent by everyone in writing clients, gateways, servers, doing
stats, handling administrative detail, installing clients, etc., there
has been no cost associated with this effort. We're proving by
experiment that the power needed to crack DES keys with brute force is
readily available, even to pedestrian hackers.

With an investment of as little as $400 on some basic FPGA equipment,
this problem can be solved at a much greater speed. With a bigger
FPGA, or use of ASIC, the speed with which keys can be found by brute
force is frightening, and when considered on a per-key basis,
frighteningly cheap (as low as $0.08 per key).

But we're not spending $100,000 on ASIC DES key cracking equipment.
We're using regular desktop computers for the most part, using cycles
that would otherwise go unused. If we really were bad guys out to do
bad things, it would certainly be worth our while to spend a few
thousand bucks... we could illicitly make that much back, many times

(Was it G. Gordon Liddy who said that we have criminals because crime
pays? Using strong crypto can make these criminals unable to do their
badness: simply using large enough keys renders all the computing
power in the world useless in finding the right one to do much damage.)

Matt Curtin  Chief Scientist Megasoft Online    I speak only for myself
Death to small keys.  Crack DES NOW!