Game of Hunt

A Cryptic Voyage

Category: forensic
Challenge file: upsidedown.txt

Solution:

1. View the content of upsidedown.txt

00000000 00000000 00000000 00000001 01000001 10101101 00000000 00000000 00101010 00100000 00000000 01100101 00000000 01100101 00000000 00000000 00000000 00000000 00000110 00000101 01001011 01010000 00000001 11011011 ...

The text file contain binary string in the format of raw representation of data.

2. Use cyberchef to convert it

[cyberchef decode binary and reverse](https://cyberchef.org/#recipe=From_Binary(‘Space’,8)Reverse(‘Byte’)

cyberchef

Next we can save the output of the file

3. Examine the download file

The file is a zip archieve file and we can unzip it

$ unzip download.zip
Archive:  download.zip
   creating: ilovepdfs/
  inflating: ilovepdfs/document_1.pdf
  inflating: ilovepdfs/document_10.pdf
  inflating: ilovepdfs/document_100.pdf
  inflating: ilovepdfs/document_11.pdf
  inflating: ilovepdfs/document_12.pdf
  inflating: ilovepdfs/document_13.pdf
  inflating: ilovepdfs/document_14.pdf
  inflating: ilovepdfs/document_15.pdf
  inflating: ilovepdfs/document_16.pdf
  inflating: ilovepdfs/document_17.pdf
  inflating: ilovepdfs/document_18.pdf
  inflating: ilovepdfs/document_19.pdf
  inflating: ilovepdfs/document_2.pdf
  inflating: ilovepdfs/document_20.pdf
  inflating: ilovepdfs/document_21.pdf
  inflating: ilovepdfs/document_22.pdf
  inflating: ilovepdfs/document_23.pdf
  inflating: ilovepdfs/document_24.pdf
  inflating: ilovepdfs/document_25.pdf
  inflating: ilovepdfs/document_26.pdf
  inflating: ilovepdfs/document_27.pdf
  inflating: ilovepdfs/document_28.pdf
  inflating: ilovepdfs/document_29.pdf
  inflating: ilovepdfs/document_3.pdf
  inflating: ilovepdfs/document_30.pdf
  inflating: ilovepdfs/document_31.pdf
  inflating: ilovepdfs/document_32.pdf
  inflating: ilovepdfs/document_33.pdf
  inflating: ilovepdfs/document_34.pdf
  inflating: ilovepdfs/document_35.pdf
  inflating: ilovepdfs/document_36.pdf
  inflating: ilovepdfs/document_37.pdf
  inflating: ilovepdfs/document_38.pdf
  inflating: ilovepdfs/document_39.pdf
  inflating: ilovepdfs/document_4.pdf
  inflating: ilovepdfs/document_40.pdf
  inflating: ilovepdfs/document_41.pdf
  inflating: ilovepdfs/document_42.pdf
  inflating: ilovepdfs/document_43.pdf
  inflating: ilovepdfs/document_44.pdf
  inflating: ilovepdfs/document_45.pdf
  inflating: ilovepdfs/document_46.pdf
  inflating: ilovepdfs/document_47.pdf
  inflating: ilovepdfs/document_48.pdf
  inflating: ilovepdfs/document_49.pdf
  inflating: ilovepdfs/document_5.pdf
  inflating: ilovepdfs/document_50.pdf
  inflating: ilovepdfs/document_51.pdf
  inflating: ilovepdfs/document_52.pdf
  inflating: ilovepdfs/document_53.pdf
  inflating: ilovepdfs/document_54.pdf
  inflating: ilovepdfs/document_55.pdf
  inflating: ilovepdfs/document_56.pdf
  inflating: ilovepdfs/document_57.pdf
  inflating: ilovepdfs/document_58.pdf
  inflating: ilovepdfs/document_59.pdf
  inflating: ilovepdfs/document_6.pdf
  inflating: ilovepdfs/document_60.pdf
  inflating: ilovepdfs/document_61.pdf
  inflating: ilovepdfs/document_62.pdf
  inflating: ilovepdfs/document_63.pdf
  inflating: ilovepdfs/document_64.pdf
  inflating: ilovepdfs/document_65.pdf
  inflating: ilovepdfs/document_66.pdf
  inflating: ilovepdfs/document_67.pdf
  inflating: ilovepdfs/document_68.pdf
  inflating: ilovepdfs/document_69.pdf
  inflating: ilovepdfs/document_7.pdf
  inflating: ilovepdfs/document_70.pdf
  inflating: ilovepdfs/document_71.pdf
  inflating: ilovepdfs/document_72.pdf
  inflating: ilovepdfs/document_73.pdf
  inflating: ilovepdfs/document_74.pdf
  inflating: ilovepdfs/document_75.pdf
  inflating: ilovepdfs/document_76.pdf
  inflating: ilovepdfs/document_77.pdf
  inflating: ilovepdfs/document_78.pdf
  inflating: ilovepdfs/document_79.pdf
  inflating: ilovepdfs/document_8.pdf
  inflating: ilovepdfs/document_80.pdf
  inflating: ilovepdfs/document_81.pdf
  inflating: ilovepdfs/document_82.pdf
  inflating: ilovepdfs/document_83.pdf
  inflating: ilovepdfs/document_84.pdf
  inflating: ilovepdfs/document_85.pdf
  inflating: ilovepdfs/document_86.pdf
  inflating: ilovepdfs/document_87.pdf
  inflating: ilovepdfs/document_88.pdf
  inflating: ilovepdfs/document_89.pdf
  inflating: ilovepdfs/document_9.pdf
  inflating: ilovepdfs/document_90.pdf
  inflating: ilovepdfs/document_91.pdf
  inflating: ilovepdfs/document_92.pdf
  inflating: ilovepdfs/document_93.pdf
  inflating: ilovepdfs/document_94.pdf
  inflating: ilovepdfs/document_95.pdf
  inflating: ilovepdfs/document_96.pdf
  inflating: ilovepdfs/document_97.pdf
  inflating: ilovepdfs/document_98.pdf
  inflating: ilovepdfs/document_99.pdf

A total of 100 pdf. Goodness gracious.

4. Examine pdf size

In the ilovepdf’s directory, check the size of each file

ls -ll

For document_83.pdf’s size appears the be more than usual compared to the rest:

.rw-r--r-- 6.3k trevorphilips 30 Sep 05:28  document_83.pdf

5. View document_83.pdf

document-83

The text is highlight in black but we can copy and paste it into a text editor

document_83.pdf’s contents:

How do you feel now, find the hidden esolang :)

++++++++++[>+>+++>+++++++>++++++++++<<<<-]>>>>+++++.++++++++
+.---.-.<---.+++++++++++++++++.--------------.>+++++++++++++.<+++++++++++++++++
++.>------------.+++++
+.<++++++.++.>---.<++++.------.>++.<+++++++++.---.------.+++++++.+
++.+++++.---------.>-.
+.+++++++++.

Appear to a brainfuck code

6. Interprete brainfuck code

Use online tools to decode it, example used is md5decrypt.net

ironCTF{You_are_the_finest}

Flag: ironCTF{You_are_the_finest}