Re: [Patents] GregNews on RSA

[Marcel Martin <mm@ellipsa.net>]

Hartmut Pilch a écrit :
> 
> Bernhard Kaindl's summary of the cyberlaw rsa page found its way into
> GregNews (http://swpat.ffii.org/players/aharonian):
> 
>     -  AN ANALYSIS OF THE EXPIRED RSA CRYPTOGRAPHY PATENT
> 
> A Web page, http://www.cyberlaw.com/rsa.html, argues that the RSA patent,
> now expired, was obviousness enough in light of the prior art to not be
> patentable, for being a variant of the Pohlig-Hellman algorithm which
> existed before RSA.
> 
>    +---------------------------------------------------------------------+
>    |  Comparison of RSA and  |                        |                  |
>    |     Pohlig-Hellman      |                        |                  |
>    |-------------------------+------------------------+------------------|
>    |                         |  RSA System            |  Pohlig-Hellman  |
>    |-------------------------+------------------------+------------------|
>    |Encryption Operation     | C = M^e mod n          |C = M^e mod p     |
>    |-------------------------+------------------------+------------------|
>    |Decryption Operation     | M = C^e mod n          |M = C^e mod p     |
>    |-------------------------+------------------------+------------------|
>    |modulus                  | p * q (prime numbers)  |p (prime number)  |
>    |-------------------------+------------------------+------------------|
>    |Encryption exponent (e)  | e relatively prime to  |e relatively prime|
>    |                         | (p-1)*(q-1)            |to (p-1)          |
>    |-------------------------+------------------------+------------------|
>    |Decryption exponent (d)  | d = e^-1 mod ((p-1)*   |d = e^-1 mod (p-1)|
>    |                         | (q-1))                 |                  |
>    +---------------------------------------------------------------------+
> 

I would like to say that there is a big difference between RSA and PH.
RSA is a so-called 'public key crypto-system', PH is not.
With RSA the exponent e is public and can be used by anybody to encrypt
a message. With PH both exponents e and d must be kept secret.
Though the mathematical descriptions of RSA and PH are almost identical, 
their uses are completely different. This could be used by the USPO to 
justify the RSA patent.

Marcel Martin