You either know, XOR you don't

Description

I've encrypted the flag with my secret key, you'll never be able to guess it. Remember the flag format and how it might help you in this challenge! 0e0b213f26041e480b26217f27342e175d0e070a3c5b103e2526217f27342e175d0e077e263451150104

I don't know

What I do know is that the flag format is crypto{...}, which we can try using

Recall due to associativity, flag ^ key = cipher means cipher ^ flag = key

from pwn import xor

HEX = "0e0b213f26041e480b26217f27342e175d0e070a3c5b103e2526217f27342e175d0e077e263451150104"

byteString = bytes.fromhex(HEX)
flagFragment = b"crypto{"

# Try XORing the flag fragment with the string to get a key fragment
print(xor(byteString, flagFragment))

We get an interesting byte string output:

b'myXORke+y_Q\x0bHOMe$~seG8bGURN\x04DFWg)a|\x1dTM!an\x7f'

We can assume the key starts with myXORkey so let's try XORing our guess with the byte string

# Test out the key
keyBit = b"myXORkey"
print(xor(keyBit, byteString))

Lo and behold, this yields the flag

Flag

crypto{1f_y0u_Kn0w_En0uGH_y0u_Kn0w_1t_4ll}