from secret import FLAG def hashfun(msg): digest = [] for i in range(len(msg) - 4): digest.append(ord(msg[i]) ^ ord(msg[i + 4])) return digest print(hashfun(FLAG)) # [10, 30, 31, 62, 27, 9, 4, 0, 1, 1, 4, 4, 7, 13, 8, 12, 21, 28, 12, 6, 60]
平文の先頭はおそらくCSR{なのでやるだけ
from ptrlib import xor keys = list(b"CSR{") ciphers = [10, 30, 31, 62, 27, 9, 4, 0, 1, 1, 4, 4, 7, 13, 8, 12, 21, 28, 12, 6, 60] for i in range(len(ciphers)): k = ciphers[i] ^ keys[i] keys.append(k) print(xor(bytes(keys), bytes(ciphers)))
