watermark_codec_pkg/watermark_codec/model_decoder.py

"""
Created on 2024/5/8
@author: <NAME>
@version: 1.0
@file: model_decoder.py
@brief 白盒水印解码器
"""
from typing import List

import numpy as np
from mindspore import nn, Tensor

from watermark_codec.tool.str_convertor import bin2string
from watermark_codec.tool.tensor_deal import load_tensor, flatten_parameters, get_prob


class ModelDecoder:
    def __init__(self, layers: List[nn.Conv2d] = None, weights: List[Tensor] = None, key_path: str = None):
        """
        初始化白盒模型解码器
        :param layers: 模型嵌入白盒水印的加密层
        :param weights: 模型嵌入白盒水印的加密层的权重，当weights不为None时，layers参数无效
        :param key_path: 投影矩阵导出文件位置，加载投影矩阵使用
        """
        # 判断传入的层是否全部为卷积层
        if layers is None and weights is None:
            raise RuntimeError('layers和weights不可同时为空')
        if weights is None:
            for layer in layers:
                if not isinstance(layer, nn.Conv2d):
                    raise TypeError('传入参数不是卷积层')
            weights = [x.weight for x in layers]  # 获取所有卷积层权重
        self.w = flatten_parameters(weights)
        self.x_random = load_tensor(key_path)
        self.model = None

    def decode(self):
        prob = get_prob(self.x_random, self.w)
        prob = prob.asnumpy()
        decode = np.where(prob > 0.5, 1, 0)
        code_string = ''.join([str(x) for x in decode.tolist()])
        code_string = bin2string(code_string)
        return code_string