Hints given to us:
Find a key.
SCMPKBOUPDPHYTIAVIVRBTMVORUDNBDFNETDOIVTXROUNDKOBFWBPVOEQLTGKKARACYCGDNAECBXIZIKPTLEERZTYCYKIVXCPKPTPOVCAQRHRVKJUWMTWCMSXKADYHRVNAHCBRVSVSSCQCZQYDJXGSNRVSWCESTTBHIFCIASXRTAHKRRTUMVOKWITZPFZDISXZVVLGETPPLKSELDPGKELSHCBJBWXBIFCPEZYNBWXCDYMGAOVWNDKAKKKWBBQKPTIODKMGGHRVVNHINFCQESDYMLACVVBWBBQROPBBDFOXOSKDIGZWXFNTKFYIICWHRVVNHIYILTKHRVXPISB
This is the original file:
File:CodeGate_2011_Crypto_200.txt
Recommended Tools:
Brains - Actually, more of guesswork.
pygenere (http://smurfoncrack.com/pygenere/pygenere.php) - For cracking ciphertext using Vigenere cipher.
Finding the "Cipher" behind the Puzzle:
Looking at the given ciphertext, it seems to strongly suggest that it could be a polyalphabetic cipher.
This time round, i made use of www.simonsingh.net again to check which cipher it could be using.
Finally, i tried Vigenere cipher using the following link.
http://www.simonsingh.net/The_Black_Chamber/vigenere_cracking_tool.html
The returned results is as followed:
It seems to suggest that if the ciphertext is indeed using Vigenere cipher, the possible key length is 2,3 or 6.
Final Solution:
So using pygenere (http://smurfoncrack.com/pygenere/pygenere.php), i've tried entering explicitly 2 followed by 3 and 6 as the keylength.
Only keylength, 6, give me back sensible english words like the following picture.
On top of the page is the returned keyword that pygenere returned to me. So i've tried that as the key and Bingo.
Using "KRIPTO", we solve this challenge. :D
cheers
0x4a61636f62
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