On 2011-05-17 8:55 AM, David-Sarah Hopwood wrote:
On 03/05/11 19:59, Zooko O'Whielacronx wrote:
Have you seen DJB's "Irrelevant patents on elliptic-curve cryptography"
http://cr.yp.to/ecdh/patents.html
[...]
My Curve25519 software never computes y, so it is not covered by the
patent. It should, in any case, be obvious to the reader that a patent
cannot cover compression mechanisms published seven years before the
patent was filed.
"""
DJB also has this page, which goes into more detail about 6141420:
http://cr.yp.to/patents/us/6141420.html
Contrary to the "filed 1994.07.29" above, the patent was actually
filed January 29, 1997:
http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=6,141,420.PN.&OS=PN/6,141,420&RS=PN/6,141,420
True, but it has the "related U.S. patent document" with application number
282263, which was filed in July 1994. That date is what is most relevant
for the "published seven years before the patent was filed" comment.
Which means it expires January 29, 2017.
If a granted patent has prior art for a given claim, then it is invalid
for that claim, and cannot be infringed, so its expiration date is not
important. (The holder can of course claim that it is infringed, but they
could do that for any random patent they hold, regardless of relevance.)
The most useful fact in the above link is that the best method for point
compression of elliptic curves, in all elliptic curves and any elliptic
curve, was published in 1992, 19 years ago. (x plus one bit that
discriminates between the two y values)
Since then, people have been publishing uselessly weird and complicated
ways of compressing points on an elliptic curve, and then claiming that
since they have a patent for some obscure, complicated, and useless ways
of compressing a point in certain obscure and arcane special cases,
anyone who compresses points has to pay them money.
Which is typical of the vast majority of patents.
_______________________________________________
cryptography mailing list
[email protected]
http://lists.randombit.net/mailman/listinfo/cryptography
