[RC5] Golomb Rulers (was "sexy" projects)

Thomas Womack thomas.womack at merton.oxford.ac.uk
Wed Mar 4 01:56:50 EST 1998


>For the former (weakness of 3DES), I'm referring to a pre-print I have
lying >around here somewhere.  I'll try to dig it up and get the author's
permission to >quote more of it.

Please do; if 3DES is as insecure as you're suggesting, we have a slight
problem. Because 3DES is what's used to secure such trivialities as the
master keys to the world's ATM networks.

>     For the latter, please review
>     http://www.zdnet.com/zdnn/content/pcwo/0226/288730.html
>     To represent the "march of progress", move each row, to the right of
>     the budget column up ~2.5 lines.

Um, that address is the DES][-solved press release, and utterly lacking in
budget columns. I presume you're pointing at the well-known table of the
costs of attacks on symmetric cryptosystems ('$300 million breaks 80-bit
keys at a rate of one every six months').

The problem is that it's just not true that, if you can do a problem in 1
minute with $10^7 worth of ASICs, you can do it in 10^4 minutes with $10^3
worth of ASICs - because $10^3 buys you no ASICs at all. There are minimum
orders at play here, and the minimum orders are quite large, and the
price-per-unit drops sharply if you order lots. $10^7 might well buy you
10^6 chips - but $10^5 will only buy you the masks, and not a single chip.

Tom
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