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Re: [Fwd: Re: P1363: prudent fields]
Composite exponents permit implementation using field
towers and lead to performance advantages.
Hilarie
>>> Sandy Harris <sandy@storm.ca> 06/26/01 11:48AM >>>
Hilarie Orman wrote:
>
> Given that the groups have no demonstrated mathematical
> weaknesses
However, enough problems with composite exponents have shown up
that we just got this advice from a wel--known crytographer:
| More generally, we recommend that elliptic curves over GF(2^n)
| where be n is composite be avoided, including elliptic curves
| over GF(2^185).
> and that they have significant computational performance advantages,
If performance depends only on the size of exponent, then those
groups -- 2^155 and 2^185 -- have about the same performance as
the group using 2^163.
> there appears to be no reason to drop them.
I'd say there's enough doubt that the cautious course would be to
drop them.