Monday, July 15, 2013

Cyberlympics 2013 Practice Round 1 write-up

Team gula.sh is participating in the Global Cyberlympics 2013 games, and we have been doing a little practicing before the first round.

Although we missed the practice rounds (I didn't get any e-mails, some of my teammates did...), thanks to my friend Hari from the Indian *.* null team, we obtained the practice round challenge package and played with it a little.

A very quick write-up on the challenges:

DECODE_ME01.txt
Base64 encoded.
Solution: WELCOME TO THE JUNGLE, WE HAVE FUN AND GAMES, SOME OF THEM ARE EVEN STAEJRWU.

DECODE_ME02.txt
Reversed String.
Solution: THIS OLD MAN, HE HAD FUN, HE PLAYED BOUTDTMS ON MY THUMB.

DECODE_ME03.txt
Digraph (a pair of characters used to write one).
Solution: sometimes the older ways are the better ways, this eimwetot is not one of them.

DECODE_ME04.txt
It was a text in hex.
Solution: I ONCE TRIED TO COUNT IN HEXADECIMAL BUT I KEPT LOOSING COUNT AFTER XUNEFILM.

DECODE_ME05.txt
Morse code.
Solution: BEEPBOOPBEEPSOUNDSLIKER2D2ISHAVINGAFITMAYBEITISBECAUSEIEIBSMSCMADEHIM

DECODE_ME06.txt
It was a text in binary.
Solution: IF YOU ADD UP ALL THE ONES IN THIS MESSAGE IT SPELLS SNFNLEGI IN EBCDIC.

DECODE_ME07.txt
URL Encoded.
Solution: TOO MANY TIMES I LOOK INTO THE FACE OF OBEMTGOE AND REALIZE THAT I AM STARING BACK AT MYSELF.

DECRYPT_ME01.txt
Caesar cipher.
Solution: IF YOU KEEP DECRYPTING ME LIKE THAT I THINK I AM GOING TO YGTRIPLO ALL OVER THE PLACE!

DECRYPT_ME02.txt
Caesar cipher.
Solution: THERE ONCE WAS A MAN FROM NANTUCKET. WHOSE NAFCMHUE WAS SO LONG, HE COULD… KEEP YOUR MIND CLEAN!!!!

DECRYPT_ME03.txt
Caesar cipher again...
Solution: IF YOU KNEW JULIUS LIKE I KNEW NADNEJUE THEN WE WOULD NOT NEED A CASEAR CIPER AT ALL.

DECRYPT_ME04.txt
Substitution cipher.
Solution: there is something evil in the way a random substitution works, it makes kewmtyat look normal.

DECRYPT_ME05.txt
Couldn't find the solution for this one in 10 mins, so we skipped it. Anyone having the solution for this, please comment, or send it to me. Thx!

FILECARVE_ME01.zip
It was a JPEG file of a QR code.
Solution:
The order of the chunks: 7862_8200_9525_1556_5490_5706_7466_7251_1055_6218_5220
QR code raw bytes: 40 85 65 54 65 24 54 35 24 10 ec 11 ec 11 ec 11 ec 11 ec 
QR code raw text: VUFRECRA

FILECARVE_ME02.zip
2 JPEG files, one was a cute bunny, the other one was a QR code again.
Solution:
Chunk order for the bunny: 4192_9117_7715_4081_2994_6501_4927_3182_4957
Chunk order for the QR code: 4901_3326_4603_1700_2737_6576_6823_5471_9316_1186_4805
QR code raw bytes: 40 95 14 15 85 54 24 14 e5 50 a0 ec 11 ec 11 ec 11 ec 11 
QR code raw text: QAXUBANU

FILECARVE_ME03.zip
I was too lazy to solve this one. It's a zip file, with a JPEG file named FILECARVE_ME03.JPG within. Again, if you have the solution, please comment, or send it to me. Thx!
Solution:
Thanks to Uuganjargal Amarsaikhan, The order of the chunks for this one is:
2143_0642_5467_5354_5149_0291_5335_7886_9524_4489_7997_4970_7077_6059_0284_7195_0794_6232_1519_7873_6639_7656_8091_0584_7866_3845_7804_2193_9518_7702
QR code raw bytes: 40 95 95 55 05 24 55 34 54 e0 a0 ec 11 ec 11 ec 11 ec 11
QR code raw text: YUPRESEN

FILECARVE_ME04.zip
I was too lazy to solve this one too. It's an mp3 file, and I think it's morse code. Once again, if you have the solution, please comment, or send it to me. Thx!
Solution:
Again, thanks to Uuganjargal Amarsaikhan, the order of the chunks for this one is: 1899_3173_4732_4730_2453_7774_4131_6350_2981_0379
Morse text in the MP3 file: CHUCAPHU

6 comments :

  1. FILECARVE_ME4
    That one was mp3 file of morse sound.
    Order of files:
    1899_3173_4732_4730_2453_7774_4131_6350_2981
    Morse text: CHUCAPHU

    ReplyDelete
  2. FILECARVE_ME03
    This zip file contains FILECARVE_ME03.jpg which is QR code.
    Order of files:
    2143_0642_5467_5354_5149_0291_5335_7886_9524_4489_7997_4970_7077_6059_0284_7195_0794_6232_1519_7873_6639_7656_8091_0584_7866_3845_7804_2193_9518_7702
    QR text: YUPRESEN

    FILECARVE_ME04
    That is mp3 file of morse sound.
    Order of files:
    1899_3173_4732_4730_2453_7774_4131_6350_2981_0379
    Morse text: CHUCAPHU

    ReplyDelete
    Replies
    1. Uuganjargal Amarsaikhan could you please explain us how you figured out the order for the zip file chunks?
      Thanks!

      Delete
  3. Uuganjargal Amarsaikhan: Thx! I will check these out as soon as I can! :)

    ReplyDelete
  4. Could you please explain how you figured out the order of the chunks? I'd been struggling with it for a while, and never figured out.

    ReplyDelete
    Replies
    1. Well there is no general rule, but it is something like this:

      You can identify the first chunk using the "file" program and the last chunk from its size (it is smaller than every other chunks, obviously).

      Next, I wrote a small python script that, once I choose the first chunk, generates all possible combinations with the first chunk (except the last chunk). So if the first chunk was 11111, I get files like: 11111_2222, 11111_33333, 11111_44444, etc.

      Here, it gets different depending on the file type: for pictures, you can just try to open the concatenated chunks and find the one where you have a little bigger part from the picture (so if you open the first chunk, you will see the first few lines, and with the proper chunk concatenated, you will see a bit more). In case of audio files for example, you can use Audacity to do the same thing, but you need to check the wave forms. But for other formats, you will probably need different approach.

      Once you have the next chunk, you will have to repeat the previous step of the process, and try to identify the next chunk, and than the next one, and so on.

      Hope it is clear, at least a little... :)

      Delete