This is the repository for all challenges which were simply text based.
The flag at the time could be found on the rules page for the 2016 CTF. An archival copy can be found here.
Flag: 55572e792981f50145f75649f53fcd3c
Problem: The key is not MCA-3CD9E73E
Solution: ruby -e "puts 'MCA-' + (0x3CD9E73E ^ 0xFFFFFFFF).to_s(16)"
Flag: MCA-C32618C1
This is a null cipher (https://en.wikipedia.org/wiki/Null_cipher) the result sentence is encoded into the first letter of each word in the provided sentence.
FLAG = MCA ABBFACFF
"The hour ended, running eternally south", uttered Lance, "This is never good. Kerosene's everywhere, Yikes! It's stupid man." Creating another anthropomorphic baseball bat for another creepy, freaky fella. Yippy! Oscar! Umbrellas are rare except when everyone lets Canadian orangutans misspell "electroencephalograms"
They will get this
"The Resulting Key Is MCA ABBFACFF you are welcome"
Flag: MCA-ABBFACFF
The players are provided with the plaintext "Attack at dawn" and the ciphertext which is generated using a cipher. The users have to derive the key used to encrypt the text from. This could be as simple as saying:
Plaintext: "Attack at dawn" Ciphertext: "mvt-7k 5l :coo" Key: MCA-5A597C9B See http://www.cs.du.edu/~snarayan/crypt/vigenere.html for vinegere cipher
Flag: Is also the key which is MCA-5A597C9B