ALL the CTFS of Crypto2025 finally

crypto-simmetric/force-decryption/attack.py

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+#!/usr/bin/env python3
+from pwn import *
+from Cryptodome.Cipher import AES
+from Cryptodome.Random import get_random_bytes
+import os
+HOST = "130.192.5.212"
+PORT = "6523"
+server = remote(HOST, PORT)
+# I cant encrypt iamsuperadmin
+# I can encrypt a xorred version of it
+# I can generate a different IV to obtain the original iamsuperadmin?
+# (iamsuperadmin XOR something) XOR IV -> Encrypted
+# Encrypted -> Decrypted XORRED
+# P XOR S XOR IV = P'
+# S XOR IV = IV'? To give in decryption phase?
+sleepT = 1
+print(server.recv(1024))
+server.send(b'enc')
+server.send(b'\n')
+sleep(sleepT)
+print(server.recv(1024))
+
+leak = b"mynamesuperadmin"
+#XOR the leak
+payload = bytes([l ^ 1 for l in leak])
+print(f"Sending payload {payload.hex()}")
+server.send(payload.hex())
+server.send(b'\n')
+sleep(sleepT)
+mres = server.recv(1024).split(b'\n')
+print(mres)
+iv = mres[0].split(b':')[1].strip()
+iv = bytes.fromhex(iv.decode('utf-8'))
+enc = mres[1].split(b':')[1].strip()
+print(f"Received IV {iv.hex()} enc {enc}")
+#Do not touch encrypted block
+ivm = bytes([i ^ 1 for i in iv])
+print(f"Malicious IV:{ivm.hex()} len:{len(ivm)}")
+sleep(sleepT)
+server.send(b'dec\n')
+print(server.recv(1024))
+sleep(sleepT)
+server.send(enc)
+server.send(b'\n')
+sleep(sleepT)
+print(server.recv(1024))
+server.send(ivm.hex())
+server.send(b'\n')
+sleep(sleepT)
+print(server.recv(1024))
+#string = "6c786f606c64727471647360656c686\n"
+#string = bytes.fromhex(string)
+#Maybe like an inverse known text attack?
+# I can decrypt with the same key and IV multiple given cipherblock
+ #to obtain the key?
+# P ----> C1
+# P2 ----> C2 L
+
+"""leak = b"mynamesuperadmin"
+#XOR the leak
+payload = bytes([l ^ 1 for l in leak])
+print(f"leak:{leak.hex()} len:{len(leak)}")
+print(f"payload:{bytes.fromhex(payload.hex())}")
+#XOR the original IV
+iv = b""
+ivm = bytes([i ^ 1 for i in iv])
+print(f"Malicious IV:{ivm.hex()} len:{len(ivm)}")
+"""

crypto-simmetric/force-decryption/chall.py

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+from Cryptodome.Cipher import AES
+from Cryptodome.Random import get_random_bytes
+#from secret import flag
+
+key = get_random_bytes(16)
+leak = b"mynamesuperadmin"
+
+
+def make_cipher():
+    IV = get_random_bytes(16)
+    cipher = AES.new(key, AES.MODE_CBC, IV=IV)
+    return IV, cipher
+
+
+def encrypt():
+    string = input("What do you want to encrypt?\n> ")
+    #string = leak
+    #stringX = bytes(([s ^ 1 for s in string]))
+    string = bytes.fromhex(string)
+    #string = stringX
+    if len(string) != 16:
+
+        print("Sorry, you can encrypt only 16 bytes!")
+        return
+
+    if leak == string:
+        print("Sorry, you can't encrypt that!")
+        return
+
+    IV, cipher = make_cipher()
+    encrypted = cipher.encrypt(string)
+
+    print(F"IV: {IV.hex()}\nEncrypted: {encrypted.hex()}\n")
+
+
+def decrypt():
+    string = input("What do you want to decrypt?\n> ")
+    string = bytes.fromhex(string)
+
+    IV = input("Gimme the IV\n> ")
+    IV = bytes.fromhex(IV)
+
+    if (IV == leak):
+        print("Nice try...")
+        return
+
+    cipher = AES.new(key, AES.MODE_CBC, IV=IV)
+
+    decrypted = cipher.decrypt(string)
+    if leak == decrypted:
+        print(f"Good job. Your flag: PUPPA")
+    else:
+        print(f"Mh, a normal day.\nDecrypted: {decrypted.hex()}")
+
+
+if __name__ == '__main__':
+    menu = \
+        "What do you want to do?\n" + \
+        "quit - quit the program\n" + \
+        "enc - encrypt something\n" + \
+        "dec - decrypt something\n" + \
+        "help - show this menu again\n" + \
+        "> "
+
+    while True:
+        cmd = input(menu).strip()
+
+        if cmd == "quit":
+            break
+        elif cmd == "help":
+            continue
+        elif cmd == "enc":
+            encrypt()
+        elif cmd == "dec":
+            decrypt()
+        elif cmd == "crack":
+            decrypt(encrypt())

crypto-simmetric/force-decryption/lecture.py

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+#!/usr/bin/env python3
+
+import os