[HARDWARE] ongoing work

Totermann harbnger at intersurf.com
Tue Apr 27 19:45:07 EDT 1999


There's only one probem with that... As I believe it, this competition is about
doing it via the "Brute Force" method, without using any special tricks.  This shows
the *minimum* average time required to crack a given code.  This time is then used
to intimidate cypher designers to come up with bigger & better cyphers.

Robert Norton wrote:

> Hi Matt,
>
> I'm guessing the first 64 bits would be "The unkn" if 8 bit bytes are
> being used.  I think the big flaw in trying to go backwards is that
> you can know that A exclusive-or'ed with B is a 1, and still not
> know what either A or B is.
>
> Still, I had an idea somewhat along those lines.  If RC5 is a giant
> mix master of the bits, it does so by going along many steps of
> blending.  If you could run backwards from the final one step, and
> still know some of the bits, say maybe 20 of the 64, then you could
> do a encoding pass up to just befoe the last step, and check only
> those 20 bits that are known.
>
> If the thing matches, then you have a code worth doing all the way,
> you will only have to redo going all the way once per million tries
> on the average, and all the other 999,999 tries will be shorter by
> one step, thus speeding up the process as a whole.
>
> Possible?  Comments?
>
> Bob Norton.
>
> Matthew Smart wrote:
>
> > But RC5 is a symmetric algorithm, so decrypting is just as easy as
> > encrypting.  And you only need to decrypt/encrypt the first block (64 bits)
> > and compare it against the ASCII representation of "The ", which is the
> > first part of "The unknown message is: ".
> >
> > So encrypting "The " and comparing against the given cyphertext should be
> > the same as decrypting the first block of the cyphertext and comparing
> > against "The ".
> >
> > mattSMART
> >
> > -----Original Message-----
> > From: owner-hardware at lists.distributed.net
> > [mailto:owner-hardware at lists.distributed.net]On Behalf Of Darxus
> > Sent: Tuesday, April 27, 1999 2:13 PM
> > To: hardware at lists.distributed.net
> > Subject: Re: [HARDWARE] ongoing work
> >
> > On Tue, 27 Apr 1999, Matthew Smart wrote:
> >
> > > I just subscribed to this list.  Are there any people who are actually
> > > running RC5 cracking hardware they created?  Are there ongoing projects?
> > >
> > > I'm currently working with another grad student to create a Verilog model
> > of
> > > an RC5-32/12/x encrypt/decrypt engine.
> >
> > http://www-inst.eecs.berkeley.edu/~barrel/rc5.html
> >
> > > One more question: from the client source code it looks like the clients
> > do
> > > encryption then compare instead of doing decryption.  Any specific reason
> > > why?
> >
> > These are all one way encryption.  Unless you break it (which to our
> > knowledge has not been done), it can not be decrypted.
> >
> > Your are correct in your interpretation of the code.
> > __________________________________________________________________
> > PGP fingerprint = 03 5B 9B A0 16 33 91 2F  A5 77 BC EE 43 71 98 D4
> >             darxus at op.net / http://www.op.net/~darxus
> >                         Pain makes you real.
> >
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