Difference between revisions of "CHES2015 Writeup"
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Revision as of 23:43, 11 August 2015
CHES 2015
Ongoing! Writeups will be published only on 13/09/2015, obviously!
On https://ches15challenge.com/ four challenges were made available on 24/06/2015 21:00 CET and the CTF was open till 13/09/2015 8:00 CET, first day of the CHES2015 conference.
A backup is available here but the third challenge is online and needs the corresponding server to be up and running.
The Challenge is composed of 4 sub-challenges, which can be solved in any order. Each comes with at least one ciphertext, which contains a secret flag. Except if stated otherwise by the challenge itself, the ciphertext has been obtained thanks to an AES128 encryption in CBC mode with a null initialization vector. An intermediate flag can also appear during the resolution.
Challenge 1
slowed.wav ctxt1.txt
Challenge 2
Cseh.jpg ctxt2.txt
Challenge 3
client.c ctxt3a.txt ctxt3b
Challenge 4
rom.png ctxt4.txt
file rom.png rom.png: PNG image data, 30598 x 10240, 8-bit/color RGB, non-interlaced
That's a huge image!
To give an idea, here is a scaled-down version:
convert rom.png -resize 10% rom_scaled.png
And a zoom at scale 1:1 on the top left corner:
convert rom.png -crop 300x300-0-0 +repage rom_corner.png
