[viff-devel] Multiparty AES in less than 3 seconds per block thanks to Twisted hack

[Marcel Keller]

Hi friends of VIFF,

I've now implemented the hack I mentioned at the last SIMAP/CACE 
meeting. The quintessence of the hack is that we do network 
communication every time a multiplication or open operation is 
scheduled, not only after returning the control back to Twisted.

As you can see in the attached graphs, the results are much better and 
more accurate than without the hack. The graph also shows that inversion 
by masking still is slower than inversion by exponentiation. However, 
the gap is smaller because I optimized PRSS which is used more with 
masking than with exponentiation. I guess that masking is slower because 
it needs more local computation and the network latency between the test 
machines is quite low (about 0.1 ms), which increases the impact of 
local computations.

If you want to try out the hack yourself, you find two patches attached. 
One is against Twisted 8.2.0 and one against the current tip of my VIFF 
repository: http://hg.viff.dk/mkeller/rev/d522f9b14b49. The PRSS 
optimizations can also be found there.

Furthermore, a new version of the document describing the AES 
implementation is attached. It corrects various errors of the previous 
version.

Best regards,
Marcel


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