Re: RSA Challenges

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.

John

	Date: Wed, 7 Feb 2007 23:06:37 -0700
	From: "John L. Bass" <jbass-/[email protected]>
	Message-Id: <200702080606.l1866bm8011226-/[email protected]>
	To: [email protected], jbass-/[email protected]
	Subject: RE: Contact Form [Challenges] RC5-72 secret key challenge
	Cc: [email protected]
	
	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!
	John
	
	        Subject: RE: Contact Form [Challenges] RC5-72 secret key challenge
	        Date: Wed, 7 Feb 2007 22:03:35 -0500
	        From: "Kaliski, Burt" <[email protected]>
	        To: <jbass-/[email protected]>
	        Cc: <[email protected]>
	
	        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-/[email protected] [mailto:jbass-/[email protected]]
	        Sent: Wednesday, January 31, 2007 9:57 PM
	        To: [email protected]
	        Subject: Contact Form [Challenges] RC5-72 secret key challenge
	
	        FirstName       John~
	        LastName        Bass~
	        email   jbass-/[email protected]~
	        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
	        to
	        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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