Hash of the challenge file for verification:

    729cd42c 9fa0328d d3faa58e 5fdd80b9
    94270562 af70a380 f017bb9a 6099d742
    8865b173 824c7547 10d2ccf0 667508f4
    e7bf5f33 30660b5b 1dda4364 256926fc

response was based on the hash:

    729cd42c 9fa0328d d3faa58e 5fdd80b9
    94270562 af70a380 f017bb9a 6099d742
    8865b173 824c7547 10d2ccf0 667508f4
    e7bf5f33 30660b5b 1dda4364 256926fc

Hash of the response file for verification:

    98900cd9 b12a8619 aaa134ee e1a20ec8
    89acc1af ca5a8131 c8b92c47 60f3b6b2
    6132ec96 31c7e735 4547252f 2d578d29
    3fcb91af d797edd1 b28fef9e 7105b5b8

Blake2b hash of the new_challenge file for participant #20:

    5bfc6971 5a5f57d2 9170410c 04cfb19d
    b079de9d a94f9b81 770d7cfd 6cfb7b14
    d05e3268 596722a6 546a40b6 79194ce9
    682d3956 23a664a9 a7d836c9 67a41d7d

The above new_challenge file: https://ppot.blob.core.windows.net/public/challenge_0020

Petr's signed attestation:

Attestation to response 0019
============================

**Date:** 8 - 9 January 2020

**Name:** Petr Korolev

**Location:** Dacha under Zvenigorod, Russia

**Device(s):** Personal laptop: MacBook Pro (15-inch, 2018) (2,6 GHz 6-Core Intel Core i7, 16 GiB memory) running on macOS 10.15.2 (19C57).

**Challenge:**

Hash of the `challenge` file for verification:

729cd42c 9fa0328d d3faa58e 5fdd80b9 94270562 af70a380 f017bb9a 6099d742 8865b173 824c7547 10d2ccf0 667508f4 e7bf5f33 30660b5b 1dda4364 256926fc

**Software used:** https://github.com/kobigurk/phase2-bn254/commit/bf852c168676a7afc5dd17b47ff9b8f394aeab8a

**Response:**

Hash of the `response` file for verification:

98900cd9 b12a8619 aaa134ee e1a20ec8 89acc1af ca5a8131 c8b92c47 60f3b6b2 6132ec96 31c7e735 4547252f 2d578d29 3fcb91af d797edd1 b28fef9e 7105b5b8

An image of the hash from the ceremony was uploaded to twitter https://twitter.com/skywinder/status/1217380683489759232

**Entropy sources:** My entropy cocktail recipe: took random words and numbers from people, has them, and concat put random symbols in between.

**Time taken:** ~ 20 hours

**Side channel defenses:** Running in isolation area (on dacha). Closed all the applications, services, and daemons on the laptop and switched off the connection to the internet.

**Postprocessing:**

- Rebooted the laptop, then transferred the files to an external hard drive, plugged that into a different laptop, and uploaded them to the remote server.

Privacy Matters, enjoy!