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Powers of Tau attestation
=========================

Round: 54
Date: 2018-02-09
Principals: Jan Jancar and Jakub Rafajdus
Location: Zilina, Slovakia

Go implementation commit:
FiloSottile/powersoftau
7a08472c288cd7022c24ad01e1e181cfc47c3363

Rust implementation commit:
ebfull/powersoftau
d47a1d3d1f007063cbcc35f1ab902601a8b3bd91

sha256 challenge:
bae01c605003b5c84b38436c7a0bc31c123a3fcf049ea95ff7967c9e0d5c8baa

The BLAKE2b hash of `./response_j` is:
       44d7dd87 08d40812 6bb1b661 ac08b58a
       ee200eb9 42592c36 bfbcb3f1 e74f5b26
       07ff54d5 3ec93f98 10f88414 7a097a9d
       4596c281 42449128 2a284343 cc921b32

The BLAKE2b hash of `./response_k2` is:
       d0e254dc 319b760d 7e9f42aa fa87df46
       95c2f7ab 8eebf17c 303e5a44 e7b3c41c
       02a73eda d60c270b b6c643a7 753cb275
       f72fd24f de8b01cf 6711d83a b89795a8

sha256 ubuntu-16.04.3-desktop-amd64.iso:
1384ac8f2c2a6479ba2a9cbe90a585618834560c477a699a4a7ebe7b5345ddc1


Log
- ---

I decided to participate by producing two consecutive responses,
produced by different machines (named k and j) and implementations.
The plan was to run the Go implementation in parallel on two machines,
after they both finish, choose randomly which response and next
challenge should be used, then use the other machine and the Rust
implementation to produce the second response. See the below log and
diagram for more details on how this actually went.

All times in UTC+1. On 09.02.2018:

- 09:25 - Downloaded challenge file to an external drive.
- 11:50 - Moved to location of machine k.
- 12:00 - Started trying to cross-compile the Go implementation for
          Windows, as machine k only had it installed.
- 12:50 - Gave up on trying to cross-compile, instead downloaded a
          Ubuntu 16.04 live USB.
- 13:00 - Booted up the live USB on machine k, installed Go, compiled
          FiloSottile/powersoftau.
- 13:05 - Copied the challenge file from the external drive to both
          machines.
- 13:07 - Started computation on both machines with the Go
          implementation.
- 14:19 - Machine j finished computing.
- 14:20 - Copied the response of machine j and the next challenge
          produced to the external drive.
- 14:40 - Machine k finished computing.
- 14:45 - Copied the response of machine k and the next challenge
          produced to the external drive.
        - Flipped a coin to select which response of which machine to
          use for further computation, machine j was selected.
- 14:50 - Installed Rust on machine k live USB.
- 14:55 - Started computation on machine k, with the Rust
          implementation, using the challenge produced before by
          machine j.
- 16:40 - Uploaded the first response (produced by machine j).
- 16:45 - Machine k finished computing.
- 17:45 - Uploaded the second response (produced by machine k, based on
          the challenge produced by j first).


Diagram
- -------

              Go implementation          |     Rust implementation
              -----------------                -------------------
    ---> [Machine k] -> response_k       |
    |                -> challenge_next_k
    |                                    |
challenge           Coinflip chose j.
    |                       |            |
    |                      \ /
    ---> [Machine j] -> response_j       |
                     -> challenge_next_j --> [Machine k] -> response_k2

* response_j and response_k2 were uploaded.
* Machine j is mine, machine k is Jakub's.
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