DPAPI加密

    // <summary>
    /// Window自带加密解密DPAPI
    /// </summary>
    public class DPAPI
    {

        #region

        /// <summary>
        /// DPAPI加密
        /// </summary>
        /// <param name="pPlainText"></param>
        /// <param name="szDescription"></param>
        /// <param name="pEntropy"></param>
        /// <param name="pReserved"></param>
        /// <param name="pPrompt"></param>
        /// <param name="dwFlags"></param>
        /// <param name="pCipherText"></param>
        /// <returns></returns>
        [DllImport("crypt32.dll", EntryPoint = "CryptProtectData", SetLastError = true, CharSet = System.Runtime.InteropServices.CharSet.Auto)]
        public static extern bool DPAPIEncrypt(ref DATA_BLOB pPlainText, string szDescription, ref DATA_BLOB pEntropy, IntPtr pReserved, ref CRYPTPROTECT_PROMPTSTRUCT pPrompt, int dwFlags, ref DATA_BLOB pCipherText);

        /// <summary>
        /// DPAPI解密
        /// </summary>
        /// <param name="pCipherText"></param>
        /// <param name="pszDescription"></param>
        /// <param name="pEntropy"></param>
        /// <param name="pReserved"></param>
        /// <param name="pPrompt"></param>
        /// <param name="dwFlags"></param>
        /// <param name="pPlainText"></param>
        /// <returns></returns>
        [DllImport("crypt32.dll", EntryPoint = "CryptUnprotectData", SetLastError = true, CharSet = System.Runtime.InteropServices.CharSet.Auto)]
        public static extern bool DPAPIDecrypt(ref DATA_BLOB pCipherText, ref string pszDescription, ref DATA_BLOB pEntropy, IntPtr pReserved, ref CRYPTPROTECT_PROMPTSTRUCT pPrompt, int dwFlags, ref DATA_BLOB pPlainText);

        #endregion

        #region

        /// <summary>
        /// 密钥类型
        /// </summary>
        public enum KeyType
        {
            /// <summary>
            /// 用户存储
            /// </summary>
            UserKey = 1,
            /// <summary>
            /// 机器存储
            /// </summary>
            MachineKey
        };

        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
        public struct DATA_BLOB
        {
            public int cbData;
            public IntPtr pbData;
        }

        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
        public struct CRYPTPROTECT_PROMPTSTRUCT
        {
            public int cbSize;
            public int dwPromptFlags;
            public IntPtr hwndApp;
            public string szPrompt;
        }

        private static IntPtr NullPtr = ((IntPtr)((int)(0)));

        private static KeyType defaultKeyType = KeyType.UserKey;

        private const int CRYPTPROTECT_UI_FORBIDDEN = 0x1;
        private const int CRYPTPROTECT_LOCAL_MACHINE = 0x4;

        #endregion

        private static void InitPrompt(ref CRYPTPROTECT_PROMPTSTRUCT ps)
        {
            ps.cbSize = Marshal.SizeOf(typeof(CRYPTPROTECT_PROMPTSTRUCT));
            ps.dwPromptFlags = 0;
            ps.hwndApp = NullPtr;
            ps.szPrompt = null;
        }

        private static void InitBLOB(byte[] data, ref DATA_BLOB blob)
        {
            blob.pbData = Marshal.AllocHGlobal(data.Length);
            if (blob.pbData == IntPtr.Zero)
                throw new Exception("无法为BLOB结构分配数据缓冲区");

            blob.cbData = data.Length;
            Marshal.Copy(data, 0, blob.pbData, data.Length);
        }

        /// <summary>
        /// 加密
        /// </summary>
        /// <param name="plainText">要加密明文</param>
        /// <returns></returns>
        public static string Encrypt(string plainText)
        {
            return Encrypt(defaultKeyType, plainText, String.Empty, String.Empty);
        }

        /// <summary>
        /// 加密
        /// </summary>
        /// <param name="keyType">密钥类型</param>
        /// <param name="plainText">要加密明文</param>
        /// <returns></returns>
        public static string Encrypt(KeyType keyType, string plainText)
        {
            return Encrypt(keyType, plainText, String.Empty, String.Empty);
        }

        /// <summary>
        /// 加密
        /// </summary>
        /// <param name="keyType">密钥类型</param>
        /// <param name="plainText">要加密明文</param>
        /// <param name="entropy"></param>
        /// <returns></returns>
        public static string Encrypt(KeyType keyType, string plainText, string entropy)
        {
            return Encrypt(keyType, plainText, entropy, String.Empty);
        }

        /// <summary>
        /// 加密
        /// </summary>
        /// <param name="keyType">密钥类型</param>
        /// <param name="plainText">要加密明文</param>
        /// <param name="entropy"></param>
        /// <param name="description"></param>
        /// <returns></returns>
        public static string Encrypt(KeyType keyType, string plainText, string entropy, string description)
        {
            if (plainText == null)
                plainText = String.Empty;
            if (entropy == null)
                entropy = String.Empty;

            return Convert.ToBase64String(Encrypt(keyType, Encoding.UTF8.GetBytes(plainText), Encoding.UTF8.GetBytes(entropy), description));
        }

        /// <summary>
        /// 加密
        /// </summary>
        /// <param name="keyType">密钥类型</param>
        /// <param name="plainTextBytes">要加密明文</param>
        /// <param name="entropyBytes"></param>
        /// <param name="description"></param>
        /// <returns></returns>
        public static byte[] Encrypt(KeyType keyType, byte[] plainTextBytes, byte[] entropyBytes, string description)
        {
            if (plainTextBytes == null)
                plainTextBytes = new byte[0];
            if (entropyBytes == null)
                entropyBytes = new byte[0];
            if (description == null)
                description = String.Empty;

            DATA_BLOB plainTextBlob = new DATA_BLOB();
            DATA_BLOB cipherTextBlob = new DATA_BLOB();
            DATA_BLOB entropyBlob = new DATA_BLOB();

            CRYPTPROTECT_PROMPTSTRUCT prompt = new CRYPTPROTECT_PROMPTSTRUCT();
            InitPrompt(ref prompt);

            try
            {
                try
                {
                    InitBLOB(plainTextBytes, ref plainTextBlob);//将明文字节转换为BLOB结构。
                }
                catch (Exception ex)
                {
                    throw new Exception("无法初始化纯文本BLOB", ex);
                }

                try
                {
                    InitBLOB(entropyBytes, ref entropyBlob);//将熵字节转换为BLOB结构
                }
                catch (Exception ex)
                {
                    throw new Exception("无法初始化熵BLOB。", ex);
                }

                int flags = CRYPTPROTECT_UI_FORBIDDEN;
                if (keyType == KeyType.MachineKey)
                    flags |= CRYPTPROTECT_LOCAL_MACHINE;

                bool success = DPAPIEncrypt(ref plainTextBlob, description, ref entropyBlob, IntPtr.Zero, ref prompt, flags, ref cipherTextBlob);
                if (!success)
                {
                    throw new Exception("CryptProtectData失败", new Win32Exception(Marshal.GetLastWin32Error()));
                }

                byte[] cipherTextBytes = new byte[cipherTextBlob.cbData];
                Marshal.Copy(cipherTextBlob.pbData, cipherTextBytes, 0, cipherTextBlob.cbData);
                return cipherTextBytes;
            }
            catch (Exception ex)
            {
                throw new Exception("DPAPI无法加密数据", ex);
            }
            finally
            {
                if (plainTextBlob.pbData != IntPtr.Zero)
                    Marshal.FreeHGlobal(plainTextBlob.pbData);

                if (cipherTextBlob.pbData != IntPtr.Zero)
                    Marshal.FreeHGlobal(cipherTextBlob.pbData);

                if (entropyBlob.pbData != IntPtr.Zero)
                    Marshal.FreeHGlobal(entropyBlob.pbData);
            }
        }

        /// <summary>
        /// 解密
        /// </summary>
        /// <param name="cipherText">要解密的密文</param>
        /// <returns></returns>
        public static string Decrypt(string cipherText)
        {
            string description;
            return Decrypt(cipherText, String.Empty, out description);
        }

        /// <summary>
        /// 解密
        /// </summary>
        /// <param name="cipherText">要解密的密文</param>
        /// <param name="description"></param>
        /// <returns></returns>
        public static string Decrypt(string cipherText, out string description)
        {
            return Decrypt(cipherText, String.Empty, out description);
        }

        /// <summary>
        /// 解密
        /// </summary>
        /// <param name="cipherText">要解密的密文</param>
        /// <param name="entropy"></param>
        /// <param name="description"></param>
        /// <returns></returns>
        public static string Decrypt(string cipherText, string entropy, out string description)
        {
            if (entropy == null)
                entropy = String.Empty;

            return Encoding.UTF8.GetString(Decrypt(Convert.FromBase64String(cipherText), Encoding.UTF8.GetBytes(entropy), out description));
        }

        /// <summary>
        /// 解密
        /// </summary>
        /// <param name="cipherTextBytes">要解密的密文</param>
        /// <param name="entropyBytes"></param>
        /// <param name="description"></param>
        /// <returns></returns>
        public static byte[] Decrypt(byte[] cipherTextBytes, byte[] entropyBytes, out string description)
        {
            DATA_BLOB plainTextBlob = new DATA_BLOB();
            DATA_BLOB cipherTextBlob = new DATA_BLOB();
            DATA_BLOB entropyBlob = new DATA_BLOB();

            CRYPTPROTECT_PROMPTSTRUCT prompt = new CRYPTPROTECT_PROMPTSTRUCT();
            InitPrompt(ref prompt);
            description = String.Empty;

            try
            {
                try
                {
                    InitBLOB(cipherTextBytes, ref cipherTextBlob);
                }
                catch (Exception ex)
                {
                    throw new Exception("无法初始化密文BLOB", ex);
                }

                try
                {
                    InitBLOB(entropyBytes, ref entropyBlob);
                }
                catch (Exception ex)
                {
                    throw new Exception("无法初始化熵BLOB", ex);
                }

                int flags = CRYPTPROTECT_UI_FORBIDDEN;
                bool success = DPAPIDecrypt(ref cipherTextBlob, ref description, ref entropyBlob, IntPtr.Zero, ref prompt, flags, ref plainTextBlob);
                if (!success)
                {
                    throw new Exception("CryptUnprotectData失败", new Win32Exception(Marshal.GetLastWin32Error()));
                }

                byte[] plainTextBytes = new byte[plainTextBlob.cbData];
                Marshal.Copy(plainTextBlob.pbData, plainTextBytes, 0, plainTextBlob.cbData);
                return plainTextBytes;
            }
            catch (Exception ex)
            {
                throw new Exception("DPAPI无法解密数据", ex);
            }
            finally
            {
                if (plainTextBlob.pbData != IntPtr.Zero)
                    Marshal.FreeHGlobal(plainTextBlob.pbData);

                if (cipherTextBlob.pbData != IntPtr.Zero)
                    Marshal.FreeHGlobal(cipherTextBlob.pbData);

                if (entropyBlob.pbData != IntPtr.Zero)
                    Marshal.FreeHGlobal(entropyBlob.pbData);
            }
        }

    }