C# 字符串的加密与解密

string EncryptKey = "yeah";//定义密钥
        /// <summary>
        /// 字符串加密
        /// </summary>
        /// <param name="str">要加密的字符串</param>
        /// <returns></returns>
        private string Encrypt(string str)
        {
            DESCryptoServiceProvider desc = new DESCryptoServiceProvider();//实例化加密解密对象
            byte[] key = Encoding.Unicode.GetBytes(EncryptKey);//定义字节数组、用来存储密钥
            byte[] data = Encoding.Unicode.GetBytes(str);//定义字节数组、用来存储要解密的字符串

            MemoryStream mstream = new MemoryStream();//实例化内存流对象

            //使用内存流实例化加密流对象
            CryptoStream cstream = new CryptoStream(mstream, desc.CreateEncryptor(key, key), CryptoStreamMode.Write);
            cstream.Write(data, 0, data.Length);//想加密流中写入数据
            cstream.FlushFinalBlock();//释放加密流
            return Convert.ToBase64String(mstream.ToArray());//返回加密后的字符串

        }
        /// <summary>
        /// 字符串解密
        /// </summary>
        /// <param name="str">要解密的字符串</param>
        /// <returns></returns>
        private string Decrypt(string str)
        {
            DESCryptoServiceProvider desc = new DESCryptoServiceProvider();//实例化加密、解密对象
            byte[] key = Encoding.Unicode.GetBytes(EncryptKey);//定义字节数组用来存储密钥
            byte[] data = Convert.ToBase64String(str);//定义字节数组用来存储密钥
            MemoryStream mstream = new MemoryStream();//实例化内存流对象
            //使用内存流实例化解密对象
            CryptoStream cstream = new CryptoStream(mstream, desc.CreateDecryptor(key, key), CryptoStreamMode.Write);
            cstream.Write(data, 0, data.Length);//向解密流中写入数据
            cstream.FlushFinalBlock();//释放解密流
            return Encoding.Unicode.GetString(mstream.ToArray());
        }