Crypto - BruteForce Writeup
解密脚本
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| from Crypto.Cipher import AES
from Crypto.Util.Padding import pad
import sys
def AES_decrypt(cipher_text, key):
try:
cipher = AES.new(key, AES.MODE_ECB)
padded_text = cipher.decrypt(cipher_text)
text = unpad(padded_text, AES.block_size)
return text
except:
return None
cipher_text = b"\xe0<Z\xb3\x95\xe2%\xf7\xb1\xc66\xfe\x1d\x12\xcb\xc1[q&q\x9e\x17\xc3;\x02'\xa1m\xc4L\xca\xcdg\x1e\x8a\x97@\xd6y\x02\x0c\xcbO\x91j%4."
found = False
for k in range(1, 33554431):
key_str = str(k).encode('utf-8')
padded_key = pad(key_str, AES.block_size)
plain_text = AES_decrypt(cipher_text, padded_key)
if plain_text is not None:
try:
text = plain_text.decode('utf-8')
if 'flag' in text.lower() or 'ctf' in text.lower() or '{' in text:
print("Found key:", k)
print("Decrypted text:", text)
found = True
break
except UnicodeDecodeError:
pass
if not found:
print("Failed to decrypt. Please check the cipher_text.")
|
注：因为r是25位素数，最大不超过2的25次方33,554,432，所以key = N % r的最大值是33,554,431
感谢出题人审阅 辛苦了
