Lense Lense

Keybase proof

I hereby claim:

I am lense on github.
I am lense (https://keybase.io/lense) on keybase.
I have a public key whose fingerprint is CDC6 56E1 4573 D016 91CB 4E35 4596 4BC9 C3E2 AFE3

To claim this, I am signing this object:

Extract the key!

Written by RyanWithZombies

Update: The key is not "flag{ don't trust the Cheshire cat!! he works for the Queen of Hearts }". Sorry about that. It's an artifact from an easier version of this challenge. You need to extract key.jpg.

HINT:

CSAWLZ is a completely custom format! You won't find decompressing tools on the internet. We made it just for you. :)

First thing I did was figure out that it was a git repo, search Google for how to extract the code, and run git archive master | tar x -C code. It asks for 2 prime factors of a number which doesn't have exactly 2 prime factors, from which it can be assumed that something was wrong with the code.

Running git fsck (after more Google searching) showed 3 hashes not matching up, which means that the hash of the file contents (plus header metadata) didn't match the filename. I then read https://git-scm.com/book/en/v2/Git-Internals-Git-Objects (side-note: the Pro Git book is a fantastic introduction to and reference for git). 3 Files are corrupted: sharp.cpp in each of the 3 commits (see git log).

Then I tool a leap of faith and assumed that a single byte was wrong (corrupted, hence the SATA controller comment) in each blob, and wrote a script to brute force it. It worked for first one, and then doom had to remind me to propagate the changes: the first

We found these System/360 punch cards and we need to extract the data. We already read the data off for you.

It looks encrypted. Can you help?

HINT: This is actually encrypted. With technology and techniques that were available in 1965

HINT: https://gist.github.com/withzombies/40554f02d6c7055fb0bc punchout.tar.xz-24504ddc1e81092010497ee49fc52e1c

###Good writeup is at https://github.com/p4-team/ctf/tree/master/2015-12-05-seccon/paillier_crypto_200#eng-version

I use the fact that h=co (mod n*n) to brute force n, which took around 45 minutes.
Then I factor n to get p and q, and make into phi. Then I plug everything into the "simpler variant" on https://en.wikipedia.org/wiki/Paillier_cryptosystem

	// ==UserScript==
	// @name Automate Steam linkfilter
	// @namespace https://github.com/lense
	// @description Skip the Steam link filter on trusted domains
	// @include https://steamcommunity.com/linkfilter/?url=*
	// @version 1
	// @grant none
	// @run-at document-start
	// ==/UserScript==

	# Preface:
	# I'm not putting this online because I think it's a particularly good
	# solution--it's buggy and thrown together. I'm instead uploading it because
	# of the sheer amount of time I spent on it. Making it public makes me feel
	# better for wasting 12 or so hours of my life on this problem, to not even
	# end up getting points for it. 6 of those were after getting the flag, but
	# uppercase instead of lowercase. A significant amount of time was also spent
	# trying to use the built in parser of rubinius to at least dump the rbc
	# instructions, but I have no idea how to write Ruby, and eventually decided
	# it would be easier to rewrite everything rather than do anything in Ruby.

	#/usr/bin/env python

	from Crypto.PublicKey import RSA, DSA
	from Crypto.Random import random, atfork
	from Crypto.Cipher import PKCS1_OAEP

	import SocketServer,threading,os,time
	import socket

	from priv import privkey, privkey_enc

	#!/usr/bin/env python

	# https://github.com/pablocelayes/rsa-wiener-attack
	import RSAwienerHacker

	def int2ascii(n):
	# Cut off 0x and L
	h = hex(n)[2:-1]
	# Convert each hex byte to ascii char
	return "".join([chr(int(h[i:i+2], 16)) for i in range(0, len(h), 2)])

	SOLARIZED HEX 16/8 TERMCOL XTERM/HEX LAB RGB HSB
	--------- ------- ---- ------- ----------- ---------- ----------- -----------
	base03 #002b36 8/4 brblack 234 #1c1c1c 15 -12 -12 0 43 54 193 100 21
	base02 #073642 0/4 black 235 #262626 20 -12 -12 7 54 66 192 90 26
	base01 #586e75 10/7 brgreen 240 #585858 45 -07 -07 88 110 117 194 25 46
	base00 #657b83 11/7 bryellow 241 #626262 50 -07 -07 101 123 131 195 23 51
	base0 #839496 12/6 brblue 244 #808080 60 -06 -03 131 148 150 186 13 59
	base1 #93a1a1 14/4 brcyan 245 #8a8a8a 65 -05 -02 147 161 161 180 9 63
	base2 #eee8d5 7/7 white 254 #e4e4e4 92 -00 10 238 232 213 44 11 93
	base3 #fdf6e3 15/7 brwhite 230 #ffffd7 97 00 10 253 246 227 44 10 99