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-----Original Message-----
From: Charlie Kaufman 
Sent: Wednesday, November 09, 2005 9:54 PM
To: 'Steven M. Bellovin'; James A. Donald
Cc: [EMAIL PROTECTED]; cryptography@metzdowd.com
Subject: RE: How broad is the SPEKE patent. 

----- Steven M. Bellovin wrote:
>Radia Perlman and Charlie Kaufman invented PDM specifically as a 
>patent-free method.  However, the claim was made that it infringed the 
>SPEKE patent.  Since it wasn't patented, there was no one willing to 
>spend the money on legal fees to fight that claim, per a story I heard.

I am not aware that any claim (in the legal sense) has been made that PDM 
infringed SPEKE. Radia and I were pushing PDM in various standards bodies as a 
strong password protocol after convincing our employers not to patent it (no 
easy feat!). We were approached by David Jablon, the inventor of SPEKE but no 
longer the patent holder, who suggested that we should not assume that PDM did 
not infringe SPEKE and should not make such claims to others. This was based on 
claims in a patent filed many years before but which through various techniques 
had been prevented from issuing (a practice known as 'submarining').

While we convinced our employers not to patent the protocol, we certainly 
weren't going to get them to defend it.

That was sufficient to get us to stop promoting PDM. If anyone would like to 
pick it up, they are of course free to do so. From a legal perspective, they 
would probably have a better chance with SRP, since Stanford holds a patent and 
might be motivated to support the challenge.


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