Hack.lu Writeups

2012 CTF by Fluxfingers

It was again a great moment of fun to participate to this year's CTF organised by Fluxfingers @ Hack.lu 2012

2012 T-Shirt contest

This one is quite apart from the other challenges for several reasons:

• The challenge was actually printed on participants' t-shirts, as of last year
• Surprisingly enough, only 2 teams over the 290 who scored at least one challenge managed to solve it!! (none of the top 10, they were teams #50 and #83)
• The challenge was the only one not designed by Fluxfingers team but... by myself, with the help of Alex to design the actual T-Shirt

Still I played the ctf fairly, proof is that even my team (woyouyizhixiaomaol=我有一只小毛驴) didn't find the solution ;-)
I must admit, the challenge was easier for local people than for remote people, reason is that a list of words was written on the T-Shirt while online a patchwork of unrelated images was visible.
On first evening, as no one solved it yet, we added an extra hint in the challenge description.
On last morning, as no remote team managed to solve it, we also published a picture of the T-Shirt for remote teams. Apparently it didn't help...
Here is it:

28 - T-shirt
Same as local T-shirt challenge: https://ctf.fluxfingers.net/challenges/noclue.png 
Send your answers to (masked email on this wiki as it's too late and we hate spammers)
Hint: "It was in use sometime ago" #ctf #infosec 
Hint: https://ctf.fluxfingers.net/challenges/IMG_4924.JPG

Here is noclue.png:



Each element represents one word.
Maybe you don't guess the exact right word for each of them, maybe not exactly in the right order, but it doesn't really matter as with a few words, it's enough to find the trick as we will see later.
So if we do the exercice we get something like:
RJ45? / unicode / crypta / assyria? / creatrix / ochra / chimaera / cumulate eucrite / jana antepono / condoleo / remissus / Πελασγοί=pelasgoi / articulo / cimex lectularius
First two seems to refer to known technologies while all the rest seems mostly latin words

Second image is the T-Shirt itself and there you get the exact word list:



So actual word list is:
utp cable unicode crypta assyrius creatrix ochra chimaera cumulate antepono condoleo remissus pelasga articulo cimex

I heard many teams trying really many things in all possible directions, sometimes wrong ones but sometimes right:

• crypta => cryptography?? and people tried many different things but it's wrong: what you have is not a ciphertext as it's somehow "meaningful", not garbage as ciphertexts usually are, and moreover the first hint says "It was in use sometime ago". Which really means people used this kind of message in the past, it was not some pseudo-crypto I took of my hat.
• many saw that first three words are somehow separated from the rest, kind of header in front of a latin message
• someone interpreted it as those words are probably there to explain how to decode the latin message. And this is perfectly correct!
• but we are geeks and when we see utp cable unicode, our brain is too happy to know what they mean today while it seems hard to interpret! That's because thinking of the UTP you know and the Unicode you know is plain wrong :-) Remember the hint said it was in use sometime ago... not today and long ago they didn't know about Ethernet or UTF-8
• still in the funny interpretations, if you type the latin part in Google translate you get:
  Assyrian vault creative ochra chimera cumulatively prefer empathize newly released article bug
  and they went googling for newly released vulnerability disclosures :-)
• several teams asked me if it could be related to telegraph and Morse code: could be...

So to resume the best ideas heard so far and the hint, it's about a real system used in the past to transmit messages, maybe to do with telegraph and Morse code...
I don't know for you but when I don't know stuffs I usually ask Google...
Now it all depends which words you google for but soon or later you will see an interesting hit:


Googling for crypta assyrius creatrix: first result title is Full text of ""Unicode".: The Universal Telegraphic Phrase-book
Hey! we get something about UNICODE??? Universal Telegraphic Phrase-book??? (UTP)
Even for people having thought of telegraph it works with a completely different query, not on the message itself:
Googling for unicode telegraph: third result title is Full text of ""Unicode".: The Universal Telegraphic Phrase-book
With this link you can see it's actually using a very old phrasebook.
See? Not the Unicode your brain is wired to, Not the UTP cable it's wired to, but some telegraphic cable :-)
That page is not that easy to use as such because it's kind of pdftotext output and you miss the layout.
Click on "See other format" or google again for the book title and you can find at least two versions in pdf, much more confortable to use.
E.g. check this one online
It's presented as a code of cypher words for commercial, domestic and familial phrases in ordinary use in inland and foreign telegrams
This edition was published in 1889!
Actually it's worth reading the introduction if you're curious
Why such phrasebook? Because you had to pay per word so sending "why have you not acknowledged receipt of letter?" costed 8 times more than sending "acapnon"
Even unicode is itself in the phrasebook list, intended to be used as header of the message, with some geeky self-referencing style: to decipher this message refer to the UNICODE

And so for the message we had we get:

unicode          to decipher this message refer to the UNICODE
crypta           have been expecting to hear from you
assyrius         following is strictly confidential
creatrix         exception cannot be made
ochra            parcel is waiting remittance
chimaera         delivery can be made at once
cumulate         will bear the expense
antepono         bring home with you...
condoleo         dispose of it as you please
remissus         can you obtain good security
pelasga          be as quick as possible
articulo         come as soon as you can
cimex            describe exactly what you want

Teams had to submit this text (or slight variations of it if you started from the picture and didn't get the exact words or exact order) to the given email address to get the points.
Congrats to ChaosMonkeys and C3L, the two teams who solved this challenge!
If you tried and failed, I hope you still had fun and didn't end up totally frustrated ;-)

Any comments? Contact me