[HARDWARE] ongoing work
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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