ALL the CTFS of Crypto2025 finally

crypto-simmetric/decrypt_it_if_you_are_fast_enough/attack.py

@@ -0,0 +1,34 @@
+#!/usr/bin/env python3
+import os
+import random
+from time import time
+from pwn import *
+
+HOST = "130.192.5.212"
+PORT = "6562"
+server = remote(HOST, PORT)
+example_flag = "5377d37d23d8b447c3ad04300eaf24d033fceb109ebf764876103b150ff7693f16d220d1a56b2043f503c2fd5ebd"
+lenFlag = len(bytes.fromhex(example_flag))
+sleepT = 0.1
+print(server.recv(1024))
+sleep(sleepT)
+server.send(b'y\n')
+sleep(sleepT)
+print(server.recv(1024))
+sleep(sleepT)
+payload = b'A'*lenFlag
+server.send(payload)
+server.send(b'\n')
+
+seed = int(time.time())
+payload_enc = server.recv(1024)
+server.send(b'f\n')
+flag_enc = server.recv(1024)
+print(f"Payload:{payload_enc.split(b'\n')[0]} flagEnc:{flag_enc.split(b'\n')[0]}")
+payload_enc = bytes.fromhex(payload_enc.split(b'\n')[0].decode())
+flag_enc = bytes.fromhex(flag_enc.split(b'\n')[0].decode())
+
+ks = [ p ^ pe for p,pe in zip(payload,payload_enc)]
+flag = [ f ^ k for f,k in zip(flag_enc,ks)]
+print(bytes(flag))
+# The script sometimes fail if it goes to fast, just rerun it