from hashlib import md5
from base64 import b64decode
from base64 import b64encode
from Crypto.Cipher import AES
from Crypto.Random import get_random_bytes
from random import randrange
import string
alphabet = string.ascii_lowercase + string.ascii_uppercase + string.digits
iv = md5(b"ignis").digest()
flag = "ijctf{i am not the real flag :)}"
message = b"Its dangerous to solve alone, take this" + b"\x00"*9
keys = []
for i in range(4):
key = alphabet[randrange(0,len(alphabet))] + alphabet[randrange(0,len(alphabet))]
keys.append(key.encode() + b'\x00'*14)
for key in keys:
cipher = AES.new(key, AES.MODE_CBC, IV=iv)
flag = cipher.encrypt(flag)
for key in keys:
cipher = AES.new(key, AES.MODE_CBC, IV=iv)
message = cipher.encrypt(message)
print(f"flag= {b64encode(flag)}")
print(f"message= {b64encode(message)}")
ひとめmeet-in-the-middle attack
from Crypto.Cipher import AES
from hashlib import md5
from base64 import *
import string
message = b"Its dangerous to solve alone, take this" + b"\x00"*9
cipher = b64decode(b"NeNpX4+pu2elWP+R2VK78Dp0gbCZPeROsfsuWY1Knm85/4BPwpBNmClPjc3xA284")
iv = md5(b"ignis").digest()
alphabet = string.ascii_lowercase + string.ascii_uppercase + string.digits
table = {}
for i, c1 in enumerate(alphabet):
print(f"[+] {i+1}/{len(alphabet)}")
for c2 in alphabet:
k1 = (c1 + c2).encode() + b"\0" * 14
aes1 = AES.new(key=k1, mode=AES.MODE_CBC, IV=iv)
cipher1 = aes1.encrypt(message)
for c3 in alphabet:
for c4 in alphabet:
k2 = (c3 + c4).encode() + b"\0" * 14
aes2 = AES.new(key=k2, mode=AES.MODE_CBC, IV=iv)
cipher2 = aes2.encrypt(cipher1)
table[cipher2] = (k1, k2)
for i, c1 in enumerate(alphabet):
print(f"[+] {i+1}/{len(alphabet)}")
for c2 in alphabet:
k1 = (c1 + c2).encode() + b"\0" * 14
aes1 = AES.new(key=k1, mode=AES.MODE_CBC, IV=iv)
message1 = aes1.decrypt(cipher)
for c3 in alphabet:
for c4 in alphabet:
k2 = (c3 + c4).encode() + b"\0" * 14
aes2 = AES.new(key=k2, mode=AES.MODE_CBC, IV=iv)
message2 = aes2.decrypt(message1)
if message2 in table:
print("k1, k2: ", table[message2])
print("k3, k4: ", (k1, k2))
