ctfcrypto.py

import hashlib
import sys

def xor(s1,s2):
    return ''.join(chr(ord(a) ^ ord(b)) for a,b in zip(s1,s2))

def repeat(s, l):
    return (s*(int(l/len(s))+1))[:l]

key = sys.argv[1]
plaintext = sys.argv[2] + key
plaintext += hashlib.md5(plaintext).hexdigest()
cipher = xor(plaintext, repeat(key, len(plaintext)))
print cipher.encode('hex')

#outputs: 274c10121a0100495b502d551c557f0b0833585d1b27030b5228040d3753490a1c025415051525455118001911534a0052560a14594f0b1e490a010c4514411e070014615a181b02521b580305170002074b0a1a4c414d1f1d171d00151b1d0f480e491e0249010c150050115c505850434203421354424c1150430b5e094d144957080d4444254643