Uncle Pry's CTF Warmups - Episode #2

ctf
warmups

(Leader & Offsec Engineer) #1

Hey 0x00ers!

If you missed part one, be sure to check it out.

I’ve been playing with some new things this week and have learned a lot and so I wanted to extend the opportunity to teach you something, through a challenge.

This one is really straight forward and will play a role in our later CTF, at this moment in time I’m just helping you guys get comfortable with using Cyberchef and getting comfortable with different operations used in cryptography and forensics challenges.

I wish you luck! If you find the answer, please enclose it using the spoiler tags when you reply.


Difficulty: Easy

Mission: Decode the message!

54 61 104 57 92 70 96 77 37 57 70 68 105 58 52 69 98 84 69 44 43 70 46 109 74 69 90 101 47 36 64 59 76 37 34 68 73 106 113 69 71 86 67 103 109 65 82 99 107

EDIT: As pointed out by @lkw, the last one was actually unsolvable. My bad, here is a new one that is solvable :smiley:


#2

Are they supposed to be literal '.'s or cyberchef’s representation of any unprintable character?
i.e.


(Leader & Offsec Engineer) #3

I’ll give you a hint.

Make sure to decode it first


#4

So, they are literal '.'s? Otherwise it’s not going to decode


(Leader & Offsec Engineer) #5

This is proof this is a good exercise. Once you notice this technique you’ll be glad I put you through this pain.

Yet another hint:

Is all text UTF8?


#6

I don’t really want hints, More of an indication of whether it’s solvable.
To clarify



Hello can’t be decoded from those dots since the characters don’t actually encode to that, it’s just cyberchef trying to show the existence of a non printable byte.
The bytes are really these


(Leader & Offsec Engineer) #7

And I just looked, and you’re right.

Whoops. Sorry about that, I’ll edit it and put up a new one…


(Presumptuous Commoner) #8

Be sure to drink your Ovaltine 0x00sec!


(Leader & Offsec Engineer) #9

Congrats! Good job!

Can you post the recipe you used? And explain how you got there?


(Presumptuous Commoner) #11

In Chef format:

From_Decimal(‘Space’,false)
From_Base85(’!-u’)

In URL format:

I also tinkered with the Magic and Text Encoding Brute Force features.


#12

Hi guys, I’m new in forum and new in security information. I’m studing every day and sorry about my english. In case the hash I use hash identifier to know whats hash is. In case the Data Format is there any tool that can help me identify the format? Cyberchef can identify some formats but not all.


(Presumptuous Commoner) #13

CyberChef (https://gchq.github.io/CyberChef) has some really cool tools in it.

On a local file system, you can use things like file (https://en.wikipedia.org/wiki/File_(command)). Again, when it comes to files or file streams, you may want to learn more about “magic numbers” (https://en.wikipedia.org/wiki/List_of_file_signatures).

Not sure if that’s the context of the question you were asking, but I hope it provides some guidance.


#14

#15

Thanks PresComm :smiley:


#16

Other useful tools for files I can think of at the moment are binwalk , scalpel and, exiftool.
Also a good hex editor (I tend to use xxd and/or okteta).


(Presumptuous Commoner) #17

And on the Windows side bintext (http://b2b-download.mcafee.com/products/tools/foundstone/bintext303.zip) and HxD (https://mh-nexus.de/en/hxd/). Exiftool is universal enough.