Rating:

# aptenodytes-forsteri (597 solves, 183 points)
## Description
Here's a warmup cryptography challenge. Reverse the script, decrypt the output, submit the flag.

## Solution
After looking at the initial python file its clear that this algorithm is taking a character and turning it into another character. To find the key to this substitution cipher
I wrote a python script that prints the alphabet, and then the ciphered alphabet. I used the key to manually decode the output: IOWJLQMAGH

I could've added to the script to fully automate that process but the flag was really short so I think it was faster to just do it by hand.

Here's the script to generate the key:
python3

flag = "flag{ABCDEFGHIJKLMNOPQRSTUVWXYZ}"
letters = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
encoded = ""
for character in flag[5:-1]:
encoded+=letters[(letters.index(character)+18)%26] #encode each character
print(letters)
print(encoded)


## Flag
flag{QWERTYUIOP}

Original writeup (https://github.com/BASHing-thru-challenges/HSCTF-2021-Writeups/tree/main/crypto/aptenodytes-forsteri).