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Powers of Tau Operational Writeup
=================================

Round: 3
Date: 2017-11-12
Name: Jared Tobin
Location: Auckland, NZ

Challenge:
e712fa22f1d027a0b4ce3ef698f26d5cab07c3380e4c24a479a914c85617fd1a2960b386cceb5c94718979010a1b7ed8b6145da872f0744e06503bd664fe7283
Response:
cb48afb82ab4c476ae741633c3eb6643e7700dc7b2b4701af91e3cc932270b96c375e5f3a5c20c96fac6c9b40a5bba6c956d66f223f090c545c277aa05427757

Preparation Steps
=================

Being somewhat pressed for time and hardware, I recruited several
geographically-distributed volunteers that I know well and trust
completely to help me out.  In the end, the following volunteers were
able to get back to me in time:

* Shawn Tobin (RSA Canada)
* Fredrik Harryson (Parity Technologies)
* Jason Forbes (Kraken Sonar Systems)

I set up a private Keybase team with the above volunteers, distributed
the challenge to them over KBFS, and gave them instructions over the
team chat on how to proceed.  Each was to add entropy and compute the
response locally using whatever mechanisms they preferred (report not
required), then return their response/hash pairs to me over KBFS.  Each
member was to use the code in Sean's powersoftau repository as of commit
9e1553c437183540392a7231d0788318a19b18a3 to perform the computation.

Procedure
=========

I computed a response locally in rather mundane fashion using rustc
1.21.0 on an early-2015 model Macbook Air running Sierra.  Eventually
the volunteers managed to upload their response/hash pairs to KBFS, and
I randomly selected one of the resulting four responses to submit for my
piece of the MPC.

I uploaded the resulting response via the handy app Sean provided me with.

Side channel defences
=====================

I used broad geographical distribution and randomness to mitigate the
possibility of successful side channel attacks.  Shawn was located in
Vancouver, Canada, Fredrik was located in Malmö, Sweden, and Jason was
located in St. John's, Canada.

I selected the response to upload by pre-determining a correspondence
between names and numbers, and then walking outside and asking the first
stranger I saw to pick a number between one and four.

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