private static byte[] ProtectData(byte[] data, string name, CryptProtectDataFlags dwFlags)
{
byte[] cipherText = null;
// copy data into unmanaged memory
// DATA_BLOB CryptProtectData
DPAPI.DATA_BLOB din = new DPAPI.DATA_BLOB();
din.cbData = data.Length;
//Marshal
din.pbData = Marshal.AllocHGlobal(din.cbData);
//InPtr
//IntPtr.Zero:一OutOfMemory
if (din.pbData.Equals(IntPtr.Zero))
{
throw new OutOfMemoryException("Unable to allocate memory for buffer.");
}
Marshal.Copy(data, 0, din.pbData, din.cbData);
DPAPI.DATA_BLOB dout = new DPAPI.DATA_BLOB();
try
{
bool cryptoRetval = DPAPI.CryptProtectData(ref din, name, IntPtr.Zero, IntPtr.Zero, IntPtr.Zero, dwFlags, ref dout);
if (cryptoRetval)
{
int startIndex = 0;
cipherText = new byte[dout.cbData];
Marshal.Copy(dout.pbData, cipherText, startIndex, dout.cbData);
DPAPI.LocalFree(dout.pbData);
}
else
{
int errCode = Marshal.GetLastWin32Error();
StringBuilder buffer = new StringBuilder(256);
Win32Error.FormatMessage(Win32Error.FormatMessageFlags.FORMAT_MESSAGE_FROM_SYSTEM, IntPtr.Zero, errCode, 0, buffer, buffer.Capacity, IntPtr.Zero);
}
}
finally
{
if (!din.pbData.Equals(IntPtr.Zero))
{
Marshal.FreeHGlobal(din.pbData);
}
}
return(cipherText);
}
/// <summary>
/// 加密数据
/// </summary>
/// <param name="data">要加密的明文数据</param>
/// <param name="name">有意义的描述，此描述会加到加密后的数据中</param>
/// <param name="dwFlags">flags的位标志</param>
/// <returns></returns>
private static byte[] ProtectData(byte[] data, string name, CryptProtectDataFlags dwFlags)
{
byte[] cipherText = null;
// copy data into unmanaged memory
//DATA_BLOB结构，用于CryptProtectData参数
DPAPI.DATA_BLOB din = new DPAPI.DATA_BLOB();
din.cbData = data.Length;
//Marshal类的作用：提供了一个方法集，这些方法用于分配非托管内存、复制非托管内存块、将托管类型转换为非托管类型，
//此外还提供了在与非托管代码交互时使用的其他杂项方法。
//为din.pbData分配内存
din.pbData = Marshal.AllocHGlobal(din.cbData);
//InPtr结构:用于表示指针或句柄的平台特定类型
//分配内存错误，抛出内存不足异常
//IntPtr.Zero:一个只读字段，代表已初始化为零的指针或句柄
if (din.pbData.Equals(IntPtr.Zero))
{
throw new OutOfMemoryException("Unable to allocate memory for buffer.");
}
//将data数组中的数据复制到pbData内存指针中
Marshal.Copy(data, 0, din.pbData, din.cbData);
//声明DPAPI类的DATA_BLOB公共结构类型
DPAPI.DATA_BLOB dout = new DPAPI.DATA_BLOB();
try
{
//加密数据
bool cryptoRetval = DPAPI.CryptProtectData(ref din, name, IntPtr.Zero, IntPtr.Zero, IntPtr.Zero, dwFlags, ref dout);
//判断加密是否成功
if (cryptoRetval) // 成功
{
int startIndex = 0;
//分配cipherText数据元素大小为dout.cbData
cipherText = new byte[dout.cbData];
//从dout.pbData内存指针指向的内容拷贝到byte数组cipherText中
Marshal.Copy(dout.pbData, cipherText, startIndex, dout.cbData);
//从内存中释放指针指向的数据I
DPAPI.LocalFree(dout.pbData);
}
else
{
//加密失败，获得错误信息
int errCode = Marshal.GetLastWin32Error();
StringBuilder buffer = new StringBuilder(256);
//显示错误信息
Win32Error.FormatMessage(Win32Error.FormatMessageFlags.FORMAT_MESSAGE_FROM_SYSTEM, IntPtr.Zero, errCode, 0, buffer, buffer.Capacity, IntPtr.Zero);
}
}
finally
{
// 如果din.pbData非空，则释放din.pbData使用的内存
if (!din.pbData.Equals(IntPtr.Zero))
{
Marshal.FreeHGlobal(din.pbData);
}
}
//返回加密后的数据
return(cipherText);
}
