[Hardware] RSA Challenges

John L. Bass jbass at dmsd.com
Mon Jun 4 16:12:51 EDT 2007

Hi Burt,

It would have been much better to have given me notice in Feb
that this would be cancelled, when I provided you some clues about
my line of attack. Did you also conclude this is potentially a much
more viable attack than brute force?

It's certainly not computationally easy either, but appears so far
much better than a 2^N counter. The electric bill for nibbling away
at it term by term hasn't been cheap either.


	Date: Wed, 7 Feb 2007 23:06:37 -0700
	From: "John L. Bass" <jbass at dmsd.com>
	Message-Id: <200702080606.l1866bm8011226 at dmsd.com>
	To: BKaliski at rsasecurity.com, jbass at dmsd.com
	Subject: RE: Contact Form [Challenges] RC5-72 secret key challenge
	Cc: rsa-labs-info at rsasecurity.com
	Thanks Burt,
	This is an interesting challenge, but if I get that far, then
	likely I'd not share that until it hit pay dirt one way or the
	other. It would certainly have to be worth something to someone,
	if RSA isn't interested in paying for the months of work.
	Have fun!
	        Subject: RE: Contact Form [Challenges] RC5-72 secret key challenge
	        Date: Wed, 7 Feb 2007 22:03:35 -0500
	        From: "Kaliski, Burt" <BKaliski at rsasecurity.com>
	        To: <jbass at dmsd.com>
	        Cc: <rsa-labs-info at rsasecurity.com>
	        We're expecting to see the key -- but if you did happen to recover the
	        full plain text (and possibly the SBox values) without recovering the
	        key, we'd be interested in hearing about that as well, especially how
	        you did it.
	        -- Burt
	        -----Original Message-----
	        From: jbass at dmsd.com [mailto:jbass at dmsd.com]
	        Sent: Wednesday, January 31, 2007 9:57 PM
	        To: rsa-labs-info at rsasecurity.com
	        Subject: Contact Form [Challenges] RC5-72 secret key challenge
	        FirstName       John~
	        LastName        Bass~
	        email   jbass at dmsd.com~
	        subject Contact Form [Challenges] RC5-72 secret key challenge~
	        contact_topic   Challenges~
	        contact_subject RC5-72 secret key challenge~
	        Comments          Would it be enough to simply provide the full plain
	        text for
	        the cipher text of the challenge, or must the key actually be provided
	        win?    I'm considering other brute force FPGA based ways to approach a
	        solution, which may not easily allow reconstructing the original
	        encryption key, just the  SBox.    Seems the intent of the challenge was
	        to prove how hard it is to recover encrypted text, not necessarily the
	        original key, as the actual challenge is worded.  The SBox is in many
	        senses, the real key, and not the seed for the scheduling hashing
	        algorithm that expands the seed and produces the SBox.    Thanks,  John

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