[RC5] DES coming...

Jocelyn Doire jdoire at cslo.consultronics.on.ca
Tue Nov 24 18:52:20 EST 1998


> Yes, it's less than two months to DES-II 3!
> Right, we are pretty much faster than in July, but can we do it in
> as few hours as 42 or even 14 ??

Glad that you brought the subject back!

If I remember correctly, someone said that we would cover the whole 
DES key space in 3 days. Judging from the RC5 key rate graph, our 
processing power will have doubled by the time DES begins. So, yes, 
there is definite hope to crack DES before the 42 hours, _provided_ 
we start _quickly_.  For that we need 3 things: 

1) Have the clients ready _before_ the start of the contest.
2) Get the clients start at the start of the contest.
3) Get the blocks in and out quickly.

To meet condition #1 goes without comments.

We can easily meet condition #2 by adding a timer into the clients
and have the key servers inform the clients of the starting time.
There time should be a bit random, and care should be given to avoid
the time zones pitfalls.

The conditions #3 is the toughest to meet and the one that will
require the most changes. In order to reduce the traffic, which will
be very heavy, especially at the start, the encrypted message and
related info should be sent only _once_, not with every block. Also
the key servers and clients should send a block range instead of one
block at a time. Finally, a block range should be obtained in
advance, before the contest start, so that the only traffic at the
beginning is the encrypted message being distributed (no blocks).

Unfortunately to implement the above suggestions, everything
component of the system must be modified, so condition #1 become
very important.

In order to debug the system, it think that it would be very good
idea to tu run a couple of full scale tests, before the real one,
maybe with the previous DES messages. Given that they would last
just a day or two, the current RC5 contest would suffer very little.

This will be the last time we will have a chance to win the DES 
contest, but if we can do it, it will be quite spectacular!

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