MGJW: this week | 信标定长(研究)

大约从上午十点多写到了下午2点半，待会儿要去开组会了

Signed-off-by: LetMeFly666 <[email protected]>

Author: LetMeFly666

tryGoPy/MGJW/thisWeek/chat.md

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+<!--
+ * @Author: LetMeFly
+ * @Date: 2025-04-20 11:00:50
+ * @LastEditors: LetMeFly.xyz
+ * @LastEditTime: 2025-04-20 14:08:53
+-->
+使用一段人类可读的描述，以一个本科生写周报的口吻，一段话详细介绍AES-CBC加密原文和密文之间的长度关系。
+要求：
+1. 凸显研究过程（探究、计算、得出结论等）
+2. 可以包含公式
+3. 以人类口吻而非机器口吻，不要列举一二三条
+
+---
+
+假设信标中每个字符由数字和字母组成（10+26=36）种，那么信标长度为$n$的情况下，有$k$封邮件随机生成的信标有重合的概率为 多少？
+
+
+很棒！返回文字和公式的latex源码。
+
+
+假设邮件有$10^{16}$封（邮件服务商提供预计可以提供1亿亿次邮件信标服且不会发生冲突），则信标长度至少要为多少才有极大概率得以保证？允许出现邮件信标冲突的概率为亿亿分之1。
+
+
+很棒！返回文字和公式的latex源码。
+
+---
+
+我使用AES加密后得到密文，如果我将密文以16进制形式显示的话，实际长度似乎要翻倍。请你设计一个较好的展示方法，目标是人类可读字符，长度尽可能地短。
+
+
+base64编码后长度能确定吗？长度和原文是什么关系？
+
+---
+
+请将一个字符串分别以AES不同方法加密，比较密文长度。
+
+写一个python脚本来展示。
+
+
+AES129  194 256的区别呢
+
+---
+
+以本科生的口吻在周报里讲base64编码，侧重原文长度和编码后的长度的关系。使用一段式描述，以人类口吻而非机器口吻，不要列举一二三条。

tryGoPy/MGJW/thisWeek/testForLength.py

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+'''
+Author: LetMeFly
+Date: 2025-04-20 11:01:24
+LastEditors: LetMeFly.xyz
+LastEditTime: 2025-04-20 11:13:19
+'''
+from Crypto.Cipher import AES
+from Crypto.Util.Padding import pad, unpad
+
+
+def encrypt_aes(plaintext: str, key: bytes) -> bytes:
+    cipher = AES.new(key, AES.MODE_CBC)  # 使用CBC模式
+    ct_bytes = cipher.encrypt(pad(plaintext.encode(), AES.block_size))
+    return cipher.iv + ct_bytes  # 返回IV + 密文
+
+msg = '其实今天要进攻'
+key = bytes.fromhex('e3a9a39b3c95c109257aeb8c09cb8ad331779647c54de1a40a66d308f8e4a882')  # 演示用，实际可别公布
+encrypted = encrypt_aes(msg, key)
+
+print(encrypted.hex())
+print(len(msg), '->', len(encrypted.hex()))
+# decrypt = decrypt_aes(encrypted, key)
+# print(decrypt)
+

tryGoPy/MGJW/thisWeek/testForLength2.py

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+'''
+Author: LetMeFly
+Date: 2025-04-20 11:01:24
+LastEditors: LetMeFly.xyz
+LastEditTime: 2025-04-20 12:10:02
+'''
+from Crypto.Cipher import AES
+from Crypto.Util.Padding import pad, unpad
+import random
+
+
+def encrypt_aes(plaintext: bytes, key: bytes) -> bytes:  # to后人：这次随机生成的直接是bytes
+    cipher = AES.new(key, AES.MODE_CBC)
+    ct_bytes = cipher.encrypt(pad(plaintext, AES.block_size))  # 因为plaintext是bytes类型，所以这里删掉了encode
+    return cipher.iv + ct_bytes
+
+def encryptOnce(msg: bytes):
+    encrypted = encrypt_aes(msg, key)
+    # print(encrypted.hex())
+    print(len(msg), '->', len(encrypted.hex()))
+
+
+key = bytes.fromhex('e3a9a39b3c95c109257aeb8c09cb8ad331779647c54de1a40a66d308f8e4a882')  # 演示用，实际可别公布
+for originalLength in range(100):
+    msg = random.randbytes(originalLength)
+    encryptOnce(msg)

tryGoPy/MGJW/thisWeek/testForLength3.py

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+'''
+Author: LetMeFly
+Date: 2025-04-20 12:57:49
+LastEditors: LetMeFly.xyz
+LastEditTime: 2025-04-20 12:57:51
+'''
+import base64
+
+# AES加密后的原始字节
+ciphertext = b'\x4d\x61\x6e\x79\x20\x73\x74\x72\x69\x6e\x67\x73'
+
+# 转换为Base64
+base64_str = base64.b64encode(ciphertext).decode('ascii')
+print(base64_str)  # 输出: TWlueSBzdHJpbmdz

tryGoPy/MGJW/thisWeek/testForLength4.py

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+'''
+Author: LetMeFly
+Date: 2025-04-20 13:42:49
+LastEditors: LetMeFly.xyz
+LastEditTime: 2025-04-20 14:07:03
+'''
+from Crypto.Cipher import AES
+from Crypto.Util.Padding import pad, unpad
+from Crypto.Random import get_random_bytes
+import base64
+
+def aes_encrypt(plaintext, mode, key, iv=None):
+    if mode == AES.MODE_ECB:
+        cipher = AES.new(key, AES.MODE_ECB)
+    elif mode == AES.MODE_CBC:
+        cipher = AES.new(key, AES.MODE_CBC, iv)
+    elif mode == AES.MODE_CFB:
+        cipher = AES.new(key, AES.MODE_CFB, iv)
+    elif mode == AES.MODE_OFB:
+        cipher = AES.new(key, AES.MODE_OFB, iv)
+    else:
+        return
+
+    padded_text = pad(plaintext.encode('utf-8'), AES.block_size)
+    ciphertext = cipher.encrypt(padded_text)
+    return ciphertext
+
+def compare_aes_modes(plaintext):
+    key = get_random_bytes(16)  # 目标是加密结果尽可能少，所以选择AES128而不是192或256
+    iv = get_random_bytes(16)
+
+    modes = [
+        ("ECB", AES.MODE_ECB),
+        ("CBC", AES.MODE_CBC),
+        ("CFB", AES.MODE_CFB),
+        ("OFB", AES.MODE_OFB)
+    ]
+    
+    print(plaintext)
+    
+    results = []
+    for name, mode in modes:
+        # ECB模式不需要IV
+        iv_param = iv if mode != AES.MODE_ECB else None
+        ciphertext = aes_encrypt(plaintext, mode, key, iv_param)
+        
+        ciphertext_length = len(ciphertext)
+        base64_length = len(base64.b64encode(ciphertext))
+        
+        results.append((name, ciphertext_length, base64_length))
+        
+        print(f"\n{name}")
+        print(f"密文长度: {ciphertext_length}")
+        print(f"Base64编码后长度: {base64_length}")
+        print(f"Base64密文: {base64.b64encode(ciphertext).decode('utf-8')}")
+
+
+plaintext = "test test test test test test handsome li test "
+print(len(plaintext))
+compare_aes_modes(plaintext)