I love this! Very detailed and I was happy that someone managed to
leverage the next-challenge stuff locally during the ceremony.

Thank you!

Sean

On Fri, Feb 9, 2018 at 6:30 PM, Jan Jancar via zapps-wg
<zapps...@lists.z.cash.foundation> wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA512
>
> 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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