From: Eric Hughes <hughes@soda.berkeley.edu>
Date: Tue, 15 Jun 93 09:04:47 PDT
To: cypherpunks@toad.com
Subject: request for patent info
In-Reply-To: <199306142119.AA17206@sun.Panix.Com>
Message-ID: <9306151600.AA08672@soda.berkeley.edu>
MIME-Version: 1.0
Content-Type: text/plain


The main rationale behind granting patent monopoly is for the
disclosure of the technique to the public.  As such, patents are
public record.  There is no danger of violating copyright by
publishing patents, already public information.

Here is RSADSI's patent portfolio:

Public Key Cryptographic Apparatus and Method
("Hellman-Merkle")		No. 4,315,552

Exponential Cryptographic Apparatus and Method
("Hellman-Pohlig")		No. 4,434,414

Cryptographic Apparatus and Method 
("Diffie-Hellman")		No. 4,200,770

Cryptographic Communications System and Method 
("Rivest-Shamir-Adelman")	No. 4,405,829

Method For Identifying Subscribers And For Generating And Verifying
Electronic Signatures In A Data Exchange System
("Schnorr")			No. 4,995,082

In my own opinion, the RSA and DH patents are relatively strong, given
that they cover particular algorithms and not whole classes of
techniques.  The key word here is relative; they might not hold
themselves, but they are certainly much more likely to hold that some
of their others.

PKP makes the following statement.  This is right out of RFC-1421, one
of the Privacy Enhanced Mail (PEM) documents.

   "These patents are stated by PKP to cover all known methods of
   practicing the art of Public Key encryption, including the variations
   collectively known as El Gamal."

It is my opinion that this statement is false, and not only false, but
an improper extension of patent monopoly.

The weakest link is the Hellman-Merkle patent, which PKP uses to claim
all public key cryptography.  Public key cryptography as such is
certainly not patentable, since it is merely a collection of
characteristics of specific systems; public key cryptography is not a
specific process or method, but a collection of such processes and
methods.  Only specifics are patentable.  Public key cryptography is
an idea, and ideas are not patentable.

The next weakest link is the Hellman-Pohlig patent, which is, I
believe, that which PKP uses to claim that all uses of the discrete
log problem (e.g. El-Gamal) are also covered.  Here again, the use of
an item without reference to a specific process or machine is not
patentable.  The specific use of exponentiation in the H-P patent is
for an RSA pseudofield (i.e. mod pq), but with exponent two.

As such, if we are going to prioritize patents, I would gather them in
the order indicated.  As far as doing forward references, The H-M
patent is likely the most interesting, since it will lead to many
other patent public key ciphers.  The RSA patent is likely the next,
because it is so widely known and mathematically simple.

Eric