Thursday, June 4, 2020

#MVS2020CTF Write-Up (Egg Hunt)

This post will cover a walk through of the solutions that I was able to find for the Egg Hunt section of the 2020 Magnet Forensics Virtual Summit CTF.  This was solved using GCHQ CyberChef (https://gchq.github.io/CyberChef/).  

Egg Hunt

NOTE: The FULL block of text below IS the puzzle, for each level, please copy the NEW block of text located below the now decoded portion.

Puzzle starts here (Copy ALL text below):

Zpv ibwf gpvoe uif CMVF fhh! Uif ofyu qjfdf pg uif qvaamf jt: Mci vojs tcibr hvs UFSSB suu (gsqfsh kcfr = Cbwcb)... hvs bslh dwsqs ct hvs dinnzs wg : KK91WUvvraIuNa91paEurUvzWS9GEI5VFGPzN2qiZw4urUvzWU5zsVEuqUzzM2Iup2MurUvzWVP1sbdgNGPdqmOco2J5WR0upKTbpaJ0YHcYo29vWVJzp3SuNbJcqbquNavfWUJdrmPlN20iZw4uN2l4WVdzNUqurUXlM2guMacupLFzWVNcNVB4NGPjNxcYMaJ5rU9ho2SvWU5gpQPcqVz5rmPhNbcupLvjM2zlWU9arQ4iZwPhNbcupaT6swPzpRcuqav6qkcY
  • Quit ROMAN around and find the ONE egg - What is the color of the first egg?
BLUE - By taking the entire text from above and pasting it into the input field on CyberChef, and using the clue of ROMAN, I used the ROT13 decode option and began to change the number of rotations down.  At 12 I could see the second line decode, so using the second clue of ONE, I went to -1 and found the answer, which would lead me to see that the second question could be decoded with a plain ROT13. 


  • Last one there is a ROTten egg - What is the special word?
Onion - Again using CyberChef, we use the plain ROT13 rotation to find the flag.


  • Probably the most baseline egg - How is the Orange Egg encoded?
Base64 - With the clue of "baseline" in the question, using CyberChef and selecting Base64 decode the text is decoded.


  • Opposites Attract - What was the key used to unlock this cipher?
magnet - This key was displayed after decoding the previous text.  Once again using CyberChef, but this time using Vigenère cipher with the key of "magnet", you get the next message show in the screenshot.


  • Hey coach, I'm going to need a SUB - What is the final message of the completed egg hunt?
bean - With only the final line of the Egg Hunt left, I continued with CyberChef and began to try different ciphers.  Focusing on those that use an alphabet substitute based on the clue of "SUB".  I ultimately found Atbash Cipher which revealed the final flag.


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