一次性密码本 是一种加密数据的方法，它将无意义的随机的假数据混入数据中，从而达到加密的作用。

一次性密码本的加密操作用到的假数据必须符合3个标准：

• 假数据与原始数据长度相同，
• 假数据真正随机
• 假数据完全保密

具体的python实现如下：

from secrets import token_bytes
from typing import Tuple


def random_key(length: int) -> int:
    tb: bytes = token_bytes(length)
    return int.from_bytes(tb, "big")


def encrypt(original: str) -> Tuple[int, int]:
    original_bytes: bytes = original.encode()
    dummy: int = random_key(len(original_bytes))
    original_key: int = int.from_bytes(original_bytes, "big")
    encrypted: int = original_key ^ dummy
    return dummy, encrypted


def decrypt(key1: int, key2: int) -> str:
    decrypted: int = key1 ^ key2
    temp: bytes = decrypted.to_bytes((decrypted.bit_length() + 7) //8, "big")
    return temp.decode()


if __name__ == "__main__":
    key1, key2 = encrypt("One Time Pad!")
    result: str = decrypt(key1, key2)
    print(result)

练习

用一次性密码本方案加密并解密图像

首先，理解一下思路，就是需要将图像先转换成base64(bytes)的形式进行存储，这样方便进行转换。 之后就可以按照一次性密码本的实现。

import base64

from secrets import token_bytes
from typing import Tuple


def random_key(length: int) -> int:
    tb: bytes = token_bytes(length)
    return int.from_bytes(tb, "big")


def encrypt(original_bytes: bytes) -> Tuple[int, int]:
    dummy: int = random_key(len(original_bytes))
    original_key: int = int.from_bytes(original_bytes, "big")
    encrypted: int = original_key ^ dummy
    return dummy, encrypted


def decrypt(key1: int, key2: int) -> bytes:
    decrypted: int = key1 ^ key2
    temp: bytes = decrypted.to_bytes((decrypted.bit_length() + 7) //8, "big")
    return temp


if __name__ == "__main__":
    img = r'feng.png'

    # 图片转base64
    with open(img, 'rb') as f:
        image_base64 = base64.b64encode(f.read())
    print(image_base64)
    key1, key2 = encrypt(image_base64)

    print('key1',key1)
    print('key2',key2)
    result: bytes = decrypt(key1, key2)
    print(result)

    # 解码图片
    imgdata = base64.b64decode(result)
    # # 将图片保存为文件
    with open("temp.jpg", 'wb') as f:
        f.write(imgdata)