[cryptography] Point compression prior art?

James A. Donald jamesd at echeque.com
Fri May 27 15:29:25 EDT 2011


On 2011-05-27 11:03 PM, Zooko O'Whielacronx wrote:
> Daniel J. Bernstein wrote to me on 2011-05-14. Everything below is
> quoted from that letter. --Zooko
>
> ------- begin appended copy of letter
> Hi Zooko,
>
> I tried following up to cryptography at randombit.net but haven't taken the
> time to figure out which hoops to jump through to make messages actually
> appear there. Anyway, you have to read the "parent case" section of the
> patent:
>
>    This is a continuation of PCT/CA95/00452, filed on Jul. 31, 1995,
>    which is a continuation-in-part of Ser. No. 08/282,263, filed on Jul.
>    29, 1994, now abandoned.
>
> This means that the patent can survive prior art after July 1993, but it
> also means that the patent expires in 2014.


So there is 1992 prior art representing a point by the x coordinate, 
plus one bit selecting one of the two possible Y coordinates,

page 171 of the Harper-Menezes-Vanstone paper
     "Public-key cryptosystems with very small key
     lengths" at Eurocrypt '92,

and the patent would have expired anyway by the time someone gets around 
to suing you.

The usual pattern, however, is to simply patent something else, usually 
something with even older prior art.  I believe that the patent on 
wheels still stands.



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