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Powers of Tau Operational writeup
=================================
Round: 13
Date: 2017-11-21
Name: Tommaso Pellizzari
Location: Italy

Challenge:
75cf81add83e814a388d1392836484c81002fe2d8db2c0649077fa6e561acd62ea714d6a28776e0f83c1ead695ab30a58740341c8933cadfe67916256f6b4c29
0c7f812a2ccbdcb7161cb1149ed5916a836074508b889ec6bbc53b750cbdc1dd

Response:
8ee7f56bb57cc1f8bda9a43c193a7d8ace49aeced57350e17e3972438d837b0c5fcf2444abe1e77bd8d043c9066a9da96898571f279871396ac50d2908d30c66


Preparation
=================
I created a very plain vanilla set-up starting from
https://github.com/ebfull/powersoftau, commit
d47a1d3d1f007063cbcc35f1ab902601a8b3bd91

I built 'compute' binary running:

cargo build --release --bin=compute

rustc 1.21.0 (3b72af97e 2017-10-09)

./compute b2sum:
0860d8c9b48596c811111f20198d6ea6212889ae935dfef1f0f818b81c393e75ac6acb13fc7d061310b99b4f2cf9b25820f8d0150a8a21313c070aa45e8c511f

Then I copied the binary to a fresh USB just bought and I re-formatted it


Side-channel defences
====================
For the computation I used a very old Sony Vaio vpceb1j8e unplugging the
hard drive and booting the computer from a second fresh Lubuntu livecd usb
stick (re-formatted)
(lubuntu-17.10-desktop-amd64.iso)
md5 48703ddd81aab8dce53264cb8a8c5202
Then I copied the compute binaries and the challenge with the first USB key
into RAM and start the compute process
I have performed the full activity in person with noone in the same room


Postprocessing
==============
After ./compute was finished, I took a picture with cell of the blake2 hash
of the response. Then copied back the response file to the first USB stick
containing the binaries, and then shut down the Vaio in which the
computation occurred.
All the communication inbound and outbound has occurred through a different
computer and the 2 USB keys mentioned
I will not destroy the Vaio (I think it will not survive much longer after
the last 5 hours) therefore I'm going to leave it unplugged for the next
month
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