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从一道CTF题出发：手把手教你用Python暴力破解AES-ECB模式加密的Flag（附完整代码与避坑指南）

news 2026/5/7 21:20:15

从一道CTF题实战：Python暴力破解AES-ECB加密的完整指南

1. 题目背景与加密原理分析

这道CTF题目提供了一个AES-ECB模式的加密函数和一个被加密的flag.txt文件。我们先来看加密函数的实现：

import Crypto import PTL import base64 txt = flag # 待加密的flag def aes(txt): data = txt.encode("utf-8") key = random.randint(100000, 999999) key = str(key) + str(key) + str(key)[0:4] data = data + "It is real flag!" cipher = AES.new(key, AES.MODE_ECB) ct_bytes = cipher.encrypt(data) return ct_bytes print(aes(txt))

关键加密特点分析：

使用AES-ECB模式加密
密钥生成方式：取6位随机数，重复拼接两次后加前4位，形成16字节密钥
明文在flag后追加固定字符串"It is real flag!"
输出base64编码的加密结果

2. ECB模式的安全弱点

AES-ECB（电子密码本）模式的主要安全问题：

相同明文块产生相同密文块：ECB模式下，相同的明文块会被加密成相同的密文块
缺乏扩散性：错误不会传播到其他块
容易遭受重放攻击：攻击者可以交换密文块

针对本题的利用点：

已知明文"It is real flag!"的存在可以作为"已知明文攻击"的突破口
密钥空间有限（100000-999999），可暴力破解

3. 破解脚本编写实战

以下是完整的Python破解脚本：

from Cryptodome.Cipher import AES import base64 # 已知的加密后flag encrypted_flag = "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