At 05:50 9/03/2000 -0800, bram wrote:
>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?
If you literally mean "field", there must be a multiplicative identity,
called "1". If you calculate its additive inverse, which is surely
tractable as a one-time computation, then additive inverses generally can
be computed as x*-1, which you postulate to be easy.
Greg.
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