[viff-devel] Floating point operation [Re. to Martin's message]

[Amitabh Saxena]

Hi Martin,

> > The functionality we need is the ability to work with floating point
> > numbers.
>
> Do you mean local computations on such numbers or do you mean secret
> shared floating point numbers?

Say, if a and b are two floating point numbers that are secret-shared
between members (e.g. additively), then we want to compute:
c = a # b
where # is one of { *, / , + , - }

c should be computed to a desired degree of accuracy such that c is
secret-shared between the members at the end of the protocol. its
possible that one of {a, b} may be public but not always. It would be
nice if this can be done locally without interaction.

Current approaches based on integers arithmetic to do floating point
operations suffer from the problem of "bit-size expansion during
intermediate computations" and I see problems in scaling up. I'd like
some references that deal with this problem ('efficient MPC with
rationals'). I found one related paper called "Cryptocomputing with
rationals" published a while ago. I've not surveyed the very recent
works yet.

Thanks in advance.
Amitabh