David,
I updated the web page
(http://www.solidmatrix.com/research/asrg/asrg-ipr.html) to include prior
art. If anyone else knows of any IPR information including prior art,
please post to the list.
Yakov
At 12:29 PM 6/2/2003 -0400, David Wheeler wrote:
Vern Paxson -
Thanks for tracking patent claims. Could you also
please track evidence of previous work ("Potential Prior Art"),
so that those who are interested in potentially-invalidating
prior art can learn of them too? I think that would be very
useful information for anyone doing anti-spam research.
Hopefully, others on this list will help fill out any entries.
Here are some potential prior art entries for the Mailblocks patent,
I'm sure others here can add a few:
<p>
Challenge-response is simply an automation of the "Halt! Who goes there!"
challenge that guards have been issuing for millenia.
Thus, this patent can be challenged as a trivial automation of
previous approaches that have been used for millenia.
<p>
In 1992, Cynthia Dwork and Moni Naor of IBM
described a challenge-response system in which the sender
would be asked to process a particular solution before
the receiver would accept the email
<a href="http://research.microsoft.com/research/sv/PennyBlack/junk1.pdf";>
[Dwork 1992]</a>.
This work was publicly presented at Crypto '92.
<p>
On May 26, 1996,
<a
href="http://groups.google.com/groups?selm=4o8cqk%248ah%40dwst13.wst.edvz.sbg.ac.at&output=gplain";>
Otmar Lendl (lendl at cosy.sbg.ac.at)
posted how to implement a challenge-response system using procmail</a>.
This was publicly posted to the newsgroup "news.admin.net-abuse.misc"
as the subject "Re: Unsolicited junk email from
exd48265(_at_)interramp(_dot_)com",
message-ID
<4o8cqk$8ah(_at_)dwst13(_dot_)wst(_dot_)edvz(_dot_)sbg(_dot_)ac(_dot_)at>#1/1.
This was a simple script that accepted email that accepted email
if it came from certain sources or included a special password in the
"Subject" line; otherwise, a challenge was replied back to the original
sender.
This posting included the code to implement the approach, as a response
to another query in the newsgroup.
Indeed, there are hints that others have implemented challenge-response
systems far earlier as well.
Hope that helps, and thank you.
--- David A. Wheeler
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