c# - 如何将 C++ unsigned char* 转换为 C#？

Question

我在 C++ 中为 AES 256 加密创建了一个有效的方法:

void AES_Encrypt(unsigned char* message, unsigned char* expandedKey)
{
      unsigned char numOfRounds = 13;
      unsigned char* state = new unsigned char[16];

      AddRoundKey(state, expandedKey);
      for (int i = 0; i < numOfRounds; i++)
      {
          //bla bla
          AddRoundKey(state, expandedKey + (16 * (i + 1)));
      }

      // bla bla
      AddRoundKey(state, expandedKey + 224);
}

和

void AddRoundKey(unsigned char *state, unsigned char* roundKey)
{
    for (int i = 0; i < 16; i++)
        state[i] = state[i] ^ roundKey[i];
}

但是当我将它翻译成 C# 时:

private void AddRoundKey(byte[] state, byte[] roundKey)
{
    for (int i = 0; i < 16; i++)
        state[i] = (byte)(state[i] ^ roundKey[i]);
}

我在准确翻译的函数上遇到错误:

AddRoundKey(state, expandedKey + (16 * (i + 1)));
AddRoundKey(state, expandedKey + 224);

在这种情况下，我如何正确翻译 void AddRoundKey(unsigned char *state, unsigned char* roundKey)？

Answer 1

最简单的方法是传递偏移量:

void AddRoundKey(byte[] state, byte[] roundKey, int offset)
    {
        for (int i = 0; i < 16; i++)
            state[i] = (byte)(state[i] ^ roundKey[i + offset]);
    }

然后你调用它:

        AddRoundKey(state, expandedKey, (16 * (i + 1)));
        ...
        AddRoundKey(state, expandedKey, 244);

其他

您可以使用 unsafe关键字(注意在项目设置中启用不安全)

unsafe void AddRoundKey(byte* state, byte* roundKey)
    {
        for (int i = 0; i < 16; i++)
            state[i] = (byte)(state[i] ^ roundKey[i]);
    }

然后在你调用它的时候使用 fixed:

fixed (byte* state_pointer = state, expandedKey_pointer = expandedKey)
        {
            AddRoundKey(state_pointer, expandedKey_pointer + 244);
        }

当 state 和 expandedKey 为 byte[] 时。