From: Chris DiBona <chrisd@loc201.tandem.com>
Date: Thu, 15 May 1997 02:38:54 +0800
To: "cypherpunks@toad.com>
Subject: RE: RSA, PGP IN LEGAL FLAP OVER ENCRYPTION TECHNOLOGY
Message-ID: <01BC6054.177E3E00@marmoset.loc201.tandem.com>
MIME-Version: 1.0
Content-Type: text/plain


I don't pretend to be patent law knowledgeable, but I'll try to address this. While pure mathematics is unpatentable, the inventions based on it are not. Remembering you can't get patents on ideas, only inventions, I decided to go and check out the RSA patent and see why it has held up and been allowed renewal (no kidding. Think of all the trouble that could have been saved if renewal had been denied!)

This first thing I noticed is that not only is RSA patented, but so is Stego, under patent 5613004. The RSA patent is abstracted and here it is: 

ABSTRACT:   A cryptographic communications system and method. The system includes a
communications channel coupled to at least one terminal having an encoding device and to at
least one terminal having a decoding device. A message-to-be-transferred is enciphered to
ciphertext at the encoding terminal by first encoding the message as a number M in a
predetermined set, and then raising that number to a first predetermined power (associated with
the intended receiver) and finally computing the remainder, or residue, C, when the
exponentiated number is divided by the product of two predetermined prime numbers
(associated with the intended receiver). The residue C is the ciphertext. The ciphertext is
deciphered to the original message at the decoding terminal in a similar manner by raising the
ciphertext to a second predetermined power (associated with the intended receiver), and then
computing the residue, M', when the exponentiated ciphertext is divided by the product of the
two predetermined prime numbers associated with the intended receiver. The residue M'
corresponds to the original encoded message M. 


For the actual details of the patent go to IBM's patent server: http://patent.womplex.ibm.com/details?patent_number=4405829


Notice how careful they were to title it a "System" and a "Method". It is that they are patenting. I think if someone had good enough lawyers, they could probably challenge this patent using prior art claims, but what the hell do I know. I'm thinking however that the Secure Telephone Units had a dual key system, and were introduced by AT&T long before the RSA patent was granted, but I'm not sure. 

So indeed they are patenting the method of using the mathmatics. Which is thier invention, which is why (IMO) they were granted the patent.  

I wish that they hadn't been able to get it renewed. It would have been nice to see how RSA would do competing thier software libraries against alternative competitors. Ah well, guess we'll have to wait another 17 years. Too bad. 

  Chris DiBona

-----Original Message-----


At 19:47 5/13/97 -0700, Kent Crispin wrote:
>On Tue, May 13, 1997 at 07:11:48PM -0800, Jim Bell wrote:
>> However, I've been waiting many years for some patent-law-knowledgeable
>> person to explain why mathematics, which was widely seen as being absolutely
>> unpatentable prior to the invention of public-key cryptography, suddenly
>> became patentable just in time for RSA, etc.  
>> 
>> Until I hear such an explanation, I _DO_ begrudge RSA and others that
"right."
>
>Wow!  I agree with you!

Sit down until the feeling goes away.


Jim Bell
jimbell@pacifier.com