From: don@cs.byu.edu
Date: Thu, 31 Aug 95 04:24:22 PDT
To: cypherpunks@toad.com
Subject: Re: SSL search attack
Message-ID: <199508311118.FAA00515@wero>
MIME-Version: 1.0
Content-Type: text/plain


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From: Jiri Baum <jirib@sweeney.cs.monash.edu.au>
>So T.C.May is the same person as "Lance"?
Hey, I wanna be Lance tooooooo. Can I be Lance? Can I?


From: Jiri Baum <jirib@sweeney.cs.monash.edu.au>

>Each client could pick a segment at random, check it and then broadcast
>a NAK. Other clients would then know that the segment in question has
>been done, and avoid picking it in the future. If you are worried about

That opens it wide open to someone NAKing the keyspace where the key is.
If we're going to involve a server, might as well do the sequential job
and make it fast.


From: monty.harder@famend.com (MONTY HARDER)

TC> * For opportunistic attacks on keys in challenges, the odds are 95% that a
TC> key will be found with only twice the total effort (or time) using a
TC> totally random method of picking up keyspace to search.

>  The odds can be improved somewhat by scaling the granularity of the
>sweep to the size of the sweep. (Align larger chunks on large-chunk
>boundaries, eliminating the chance of overlap with other large chunks.)

Some kind of step (ie, round-down) function performed on the random (I
vote we call it a dart) output, with the size of the step based on the how
many segments at once you want to search? Seems to me that all your doing 
is searching an X segment area around where the dart hit. In order to
get any kind of boundry, you have to scale the allowed segment blocks, by 
powers of two, for example, or something, so everyone knows where the 
borders are. Its a nice thought but I don't see that it's necessary.

If, on the other hand, sequential searchers plow through half of the
keyspace while a "random crew" throws darts at the other half, everyone
can participate how they wish. And if the keyserver gets deep-six'd by a
Denial of Service attack (or just swamped), everyone can just switch into
random mode and shotgun the keyspace. (Maybe even avoiding what's already 
been sequentially-searched)

Don

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<don@cs.byu.edu>           fRee cRyPTo!   jOin the hUnt or BE tHe PrEY
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