AES

直接通过题目来学习

from Crypto.Cipher import AES
 import binascii
 from Crypto.Util.number import bytes_to_long
 from aes_flag import flag,key
 import os
 #maybe flag is fake
 iv = flag
 l = len(key)
 if l==16:

     hint = os.urandom(4) * 16
     print(bytes_to_long(hint)^bytes_to_long(key))

     msg = b'Welcome! Good luck have fun! diyicichutiqiuqingpen xiexiele.....'
     def encrypto(message):
         aes = AES.new(key,AES.MODE_CBC,iv)
         return aes.encrypt(message)

     print(binascii.hexlify(encrypto(msg))[-32:])

'''
10814139970454569101142970101299943513649261825483864773663646850498898172963892837254881797558641977330505910327448279013601791760702391621769017335029566
b'a99b50f2320e2768e94535cac2888a96'
'''

分析

 l = len(key)
 if l==16:
     hint = os.urandom(4) * 16
     print(bytes_to_long(hint)^bytes_to_long(key))
#key是16个字节 而hint是16个重复的4个字节
#所以hint 可以通过异或之后前面的字节求出
#key通过异或求出

# -----------get key---------
tmp = 10814139970454569101142970101299943513649261825483864773663646850498898172963892837254881797558641977330505910327448279013601791760702391621769017335029566
hint = int(str(hex(tmp))[2:10] * 16,16)
key = long_to_bytes(tmp ^ hint)

from Crypto.Util.number import long_to_bytes
import binascii, sys
from Crypto.Util.strxor import strxor
from Crypto.Cipher import AES

# -----------get key---------
tmp = 10814139970454569101142970101299943513649261825483864773663646850498898172963892837254881797558641977330505910327448279013601791760702391621769017335029566
hint = int(str(hex(tmp))[2:10] * 16,16)
key = long_to_bytes(tmp ^ hint)

# ----------get iv-----------
msg = b'Welcome! Good luck have fun! diyicichutiqiuqingpen xiexiele.....'
msgs = [msg[ii:(ii+16)] for ii in range(0,len(msg),16)]
msgs.reverse()
IV = binascii.unhexlify('a99b50f2320e2768e94535cac2888a96')

def decry(key,IV,ms):
    aes=AES.new(key,AES.MODE_ECB)
    return strxor(aes.decrypt(IV),ms)

for ms in msgs:
    IV=decry(key,IV,ms)
print(b'flag{' + IV+ b'}')