Does anybody know of a field in which a + b and a * b can be computed
quickly but (and this is important) it's computationally intractable to
compute the additive inverse of a?
I need it for a technique I'm working on.
-Bram
[Bram: All fields of n elements are isomorphic to all other fields of
n elements, and in any of the fields I'm familiar with, it is trivial
to compute an additive (or multiplicative) inverse. Given this, I
suspect what you want to do is rather hard -- you would have to
conceal the isomorphism to, say, GF(n) somehow. Any readers have any
other insights here? --Perry]
