[viff-devel] Optimizing preprocessing

[Martin Geisler]

Janus Dam Nielsen <janus.nielsen at alexandra.dk> writes:

> Hi Marcel,
>
> I am not opposed to your suggestion. However I would like to point out
> that in VIFF you compute on shares and not field elements!

Well, we've actually made the outer runtime interfaces in such a way
that add, mul, xor, etc... accept both integers, FieldElements and
Shares. The methods then wrap their input as needed -- or they *dont*
wrap it if that leads to a short cut (e.g., constant multiplication)

> Computing directly on the field elements is hacking the abstractions
> of VIFF. Computation on field elements or rather the representation of
> a Share can be useful as an optimization, however this optimization
> should be confined within applications or runtimes, and should not
> progress over interface boundaries as I fear you are suggesting.

I think we are in agreement: public methods on the runtimes will keep
returning Shares. Methods used internally in runtimes can return other
things as needed. To me it sounds like a better API to require
preprocessing functions to return a list of Deferreds:

  [D(?), D(?), ...],

instead of a Deferred list of tuples containing Deferreds :-)

I think it will simplify the interface nicely, at least for consumers.
Using simpler types also leads to less memory usage which has a positive
effect on performance, as Marcel notes. So let's go for it.

-- 
Martin Geisler

VIFF (Virtual Ideal Functionality Framework) brings easy and efficient
SMPC (Secure Multiparty Computation) to Python. See: http://viff.dk/.