🚀 go-pugleaf

In <1992Nov3.092637.42@nsrvan.vanc.wa.us> sysevm@nsrvan.vanc.wa.us writes:

>In article <1992Nov3.043722.9603@panix.com>, oppedahl@panix.com (Carl Oppedahl) writes:
>> In <Bx1o2L.AMz@access.digex.com> jthomas@access.digex.com (Joe Thomas) writes:
>> 
>>>   In all the posts I've read about PKP's patent claims over RSA public
>>>key encryption, I have never seen anyone mention when the patent is due 
>>>to expire.  I was under the impression that U.S. patent protection is only
>.
>>>somebody checks when it was filed?
>> 
>> If somebody will post the patent number I would be willing to check
>> and see when it expires.
>> 
>	Thanks Carl, Try US Patent 4,200,770 4/29/80 by Hellman, Diffie, Merkle
>and 4,218,582 8/19/80 by Hellman and Merkle.

 
Regarding US Pat. No. 4,200,770, the Derwent database says this: 
the patent issued April 29, 1980.
It is owned by Stanford University.
Inventors: HELLMAN M E; DIFFIE B W; MERKLE R C
There is also a Canadian patent, CA 1121480 issued April 6, 1982.
The first patent application was filed September 6, 1977 in the US.
Abstract: The cryptographic system transmits a computationally
    secure cryptogram over an insecure communication channel without
    prearrangement of a cipher key.  A secure cipher key is generated by
    the conversers from transformation of exchanged transformed signals.
    The conversers each posses a secret signal and exchange an initial
    transformation of the secret signal with the other converser.
         The received transformation of the other converser's secret signal
    is again transformed with the receiving converser's secret signal to
    generate a secure cipher key.  The transformations use non-secret
    operations that are easily performed but extremely difficult to invert.
    It is infeasible for an eavesdropper to invert the initial
    transformation to obtain either converser's secret signal, or duplicate 
    the latter transformation to obtain the secure cipher key.
 
The US patent should expire April 29, 1997.
-------------------------------------------
Regarding US Pat. No. 4218582, the Derwent database says this:
the US patent issued August 19, 1980.
Assignee: STANFORD UNIVERSITY
Stanford has also sought patents in Belgium, Netherlands, Great Britain,
Germany, Sweden, France, Canada, Switzerland, and Italy.
Patent Family:
    CC Number    Kind     Date  
    BE 871039      A     790405 
    NL 7810063     A     790410 
    GB 2006580     A     790502     
    DE 2843583     A     790510     
    SE 7810478     A     790514     
    FR 2405532     A     790608     
    DE 2843583     C     820603     
    DE 2857905     A     820715     
    CA 1128159     A     820720     
    GB 2006580     B     820818     
    CH 634161      A     830114     
    IT 1099780     B     850928     
The first application was filed October 6, 1977 in the US.
Abstract: Coding and decoding system for data transmission over
    unprotected lines.  The decoding system unit which has two inputs, one
    receiving the coded message and the second the authentication signal
    and has an output transmitting the inverse of the message coding
    transformation.
         The message is represented as a vector X having 'n' dimensions X1
    being equal to 0 or 1.  The authentication is represented by the vector
    n dimensions whose components are such that a1 = logba' i mod m for i -
    1,2,....n where a alpha m are whole numbers.  The coding transformation
    cannot be determined in the absence of the authentication signal.
 
The US patent is expected to expire August 19, 1997.
-------------------------------------------
Regarding US Pat. No. 4,405,829, the Derwent database says this:
the US patent issued September 20, 1983.  
It appears the application was first filed in the US on December 14, 1977.
Assignee: MASSACHUSETTS INST TECH
Inventors: RIVEST R L; SHAMIR A; ADLEMAN L M
Abstract: 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 encoding the
    message as number M in a predetermined set.  That number is then
    raised to a first predetermined power (associated with the intended
    receiver) and finally computed.  The remainder or residue, C, is
    computed 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).  The residue, M', is computed 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.
 
The US patent would be expected to expire September 20, 2000.

I fear this is more than anyone wanted to know.


Carl Oppedahl AA2KW  (intellectual property lawyer)
30 Rockefeller Plaza
New York, NY  10112-0228
voice 212-408-2578     fax 212-765-2519